UNIT-II

2. Basics of Operating System

2.1 Introduction

Modern general-purpose computers, including personal computers and

mainframes, have an operating system to run other programs, such as application

software. Examples of operating systems for personal computers include Microsoft

Windows, Mac OS (and Darwin), UNIX, and LINUX. The lowest level of any

operating system is its kernel. This is the first layer of software loaded into

memory when a system boots or starts up. The kernel provides access to various

common core services to all other system and application programs. These services

include, but are not limited to: disk access, memory management, task scheduling,

and access to other hardware devices. As well as the kernel, an operating system is

often distributed with tools for programs to display and manage a graphical user

interface (although Windows and the Macintosh have these tools built into the

operating system), as well as utility programs for tasks such as managing files and

configuring the operating system. They are also often distributed with application

software that does not relate directly to the operating system‘s core function,

various camps advocate micro-kernels, monolithic kernels, and so on. Operating

systems are used on most, but not all, computer systems. The simplest computers,

including the smallest embedded systems and many of the first computers did not

have operating systems. Instead, they relied on the application programs to manage

the minimal hardware themselves, perhaps with the aid of libraries developed for

the purpose. Commercially-supplied operating systems are present on virtually all

modern devices described as computers, from personal computers to mainframes,

as well as mobile computers such as PDAs and mobile phones.

Why Use Operating Systems

An operating system (OS) is a software program that manages the hardware and

software resources of a computer. The OS performs basic tasks, such as controlling

and allocating memory, prioritizing the processing of instructions, controlling

input and output devices, facilitating networking, and managing files. The first

computers did not have operating systems. However, software tool for managing

the system and simplifying the use of hardware appeared very quickly afterwards

and gradually expanded in scope. By the early 1960s, commercial computer

vendors were supplying quite extensive tools for streamlining the development,

scheduling, and execution of jobs on batch processing systems. Examples were

produced by UNIVAC and Control Data Corporation, amongst others. Through the

1960s, several major concepts were developed, driving the development of

operating systems. The development of the IBM System/360 produced a family of

mainframe computers available in widely differing capacities and price points, for

which a single operating system OS/360 was planned (rather than developing ad-

hoc programs for every individual model). This concept of a single OS spanning an

entire product line was crucial for the success of System/360 and, in fact, IBM‘s

current mainframe operating systems are distant descendants of this original

system; applications written for the OS/360 can still be run on modern machines.

OS/360 also contained another important advance: the development of the hard

disk permanent storage device (which IBM called DASD). Another key

development was the concept of timesharing: the idea of sharing the resources of

expensive computers amongst multiple computer users interacting in real time with

the system. Time sharing allowed all of the users to have the illusion of having

exclusive access to the machine; the Multics timesharing system was the most

famous of a number of new operating systems developed to take advantage of the

concept. Commercially-popular minicomputer operating system was VMS. One

notable early operating system was CP/M, which was supported on many early

microcomputers and was largely cloned in creating MS-DOS, which became

wildly popular as the operating system chosen for the IBM PC (IBM‘s version of it

was called IBM-DOS or PC-DOS), its successors making Microsoft one of the

world‘s most profitable companies. The major alternative throughout the 1980s in

the microcomputer market was Mac OS, tied intimately to the Apple Macintosh

computer. By the 1990s, the microcomputer had evolved to the point where, as

well as extensive GUI facilities, the robustness and flexibility of operating systems

of larger computers became increasingly desirable. Microsoft's response to this

change was the development of Windows NT, which served as the basis for

Microsoft‘s entire operating system line starting in 1999. Apple rebuilt their

operating system on top of a UNIX core as Mac OS X, released in 2001. Hobbyist-

developed reimplementation‘s of UNIX, assembled with the tools from the GNU

project, also became popular; versions based on the Linux kernel are by far the

most popular, with the BSD derived UNIX holding a small portion of the server

market. The growing complexity of embedded devices has a growing trend to use

embedded operating systems on them.

Note: Multics was an inspiration to a number of operating systems developed in

the 1970s, notably UNIX.

Present Scenario

Command line interface (or CLI) operating systems can operate using only the

keyboard for input. Modern OS‘s use a mouse for input with a graphical user

interface (GUI) sometimes implemented as a shell. The appropriate OS may

depend on the hardware architecture, specifically the CPU, with only Linux and

BSD running on almost any CPU. Windows NT has been ported to other CPUs,

most notably the Alpha, but not many. Mainframe computers and embedded

systems use a variety of different operating systems, many with no direct

connection to Windows or UNIX, but typically more similar to Unix than

Windows. Personal computers IBM PC compatible - Microsoft Windows and

smaller Unix-variants (like Linux and BSD) Apple Macintosh - Mac OS X,

Windows, Linux and BSD Mainframes - A number of unique OS‘s, sometimes

Linux and other UNIX variants. Embedded systems - a variety of dedicated OS‘s,

and limited versions of Linux or other OS‘s.

Unix-like

The UNIX-like family is a diverse group of operating systems, with several major

subcategories including System V, (Berkeley Software Distribution) BSD, and

Linux. The name ―UNIX‖ is a trademark of the open group which licenses it for

use to any operating system that has been shown to conform to the definitions that

they have cooperatively developed. The name is commonly used to refer to the

large set of operating systems which resemble the original UNIX systems run on a

wide variety of machine architectures. They are used heavily as server systems in

business, as well as workstations in academic and engineering environments. Free

software UNIX variants, such as Linux and BSD, are increasingly popular.

They are used in the desktop market as well, for example Ubuntu, but mostly by

hobbyists. Some UNIX variants like HP‘s HP-UX and IBM‘s AIX are designed to

run only on that vendor‘s proprietary hardware. Others, such as Solaris, can run on

both proprietary hardware and on commodity x86 PCs. Apple‘s Mac OS X, a

microkernel BSD variant derived from next step, mach, and free BSD, has replaced

Apple‘s earlier (non-UNIX) Mac OS. Over the past several years, free UNIX

systems have supplanted proprietary ones in most instances. For instance, scientific

modeling and computer animation were once the province of SGI‘s IRIX, present

scenario they are dominated by Linux-based. The team at bell labs who designed

and developed UNIX went on to develop and inferno, which were designed for

modern distributed environments. They had graphics built-in, unlike UNIX

counterparts that added it to the design later did not become popular because,

unlike many UNIX distributions.

Note: The first microcomputers did not have the capacity or need for the elaborate

operating system that had been developed for mainframes and minis; minimalistic

operating systems were developed.

Microsoft Windows

The Microsoft Windows family of operating systems originated as a graphical

layer on top of the older MS-DOS environment for the IBM PC. Modern versions

are based on the newer Windows NT core that first took shape in OS/2 and

borrowed from open VMS. Windows runs on 32-bit and 64-bit Intel and AMD

computers, although earlier versions also ran on the DEC alpha, MIPS, and power

PC architectures (some work was done to port it to the SPARC architecture). As of

2004, Windows held a near-monopoly of around 90% of the worldwide desktop

market share, although this is thought to be dwindling due to the increase of

interest focused on open source operating systems. It is also used on low-end and

mid-range servers, supporting applications such as web servers and database

servers. In recent years, Microsoft has spent significant marketing and R&D

money to demonstrate that Windows is capable of running any enterprise

application.

Operating System

Operating system (OS) is the lifeline of computer. You connect all the basic

devices like CPU, monitor, keyboard and mouse; plug in the power supply and

switch it on thinking you have everything in place. But the computer will not start

or come to life unless it has an operating system installed in it because OS −

Keeps all hardware parts in a state of readiness to follow user instructions

Co-ordinates between different devices

Schedules multiple tasks as per priority

Allocates resource to each task

Enables computer to access network

Enables users to access and use application software

Besides initial booting, these are some of the functions of an operating system −

Managing computer resources like hardware, software, shared resources, etc.

Allocating resources

Prevent error during software use

Control improper use of computer

One of the earliest operating systems was MS-DOS, developed by Microsoft for

IBM PC. It was a Command Line Interface (CLI) OS that revolutionized the PC

market. DOS was difficult to use because of its interface. The users needed to

remember instructions to do their tasks. To make computers more accessible and

user-friendly, Microsoft developed Graphical User Interface (GUI) based OS

called Windows, which transformed the way people used computers.

An operating system is an important part of almost every computer system. A

computer system can be divided roughly into four components: the hardware, the

operating system, the application programs, and the users (Figure below).

Figure : Abstract view of the components of a computer system.

The hardware-the central processing unit (CPU), the memory, and the input/output

(110) devices-provides the basic computing resources. The application programs-

such as word processors, spreadsheets, compilers, and web browsers-define the

ways in which these resources are used to solve the computing problems of the

users. The operating system controls and coordinates the use of the hardware

among the various application programs for the various users. The components of a

computer system are its hardware, software, and data.

The operating system provides the means for the proper use of these

resources in the operation of the computer system operating systems can be

explored from two viewpoints the user and the system.

Note: Since the early 1990s the choice for personal computers has been largely

limited to the Microsoft windows family and the UNIX-like family, of which Linux

and Mac OS are becoming the major choices.

Functions of Operating System

As you know, operating system is responsible for functioning of the computer

system. To do that it carries out these three broad categories of activities −

Essential functions − Ensures optimum and effective utilization of

resources

Monitoring functions − Monitors and collects information related to system

performance

Service functions − Provides services to users

Let us look at some of the most important functions associated with these

activities.

Processor management

Managing a computer’s CPU to ensure its optimum utilization is called processor

management. Managing processor basically involves allocating processor time to

the tasks that need to be completed. This is called job scheduling. Jobs must be

scheduled in such a way that −

There is maximum utilization of CPU

Turnaround time, i.e. time required to complete each job, is minimum

Waiting time is minimum

Each job gets the fastest possible response time

Maximum throughput is achieved, where throughput is the average time

taken to complete each task

There are two methods of job scheduling done by operating systems −

Preemptive scheduling

Non-Preemptive scheduling

Preemptive Scheduling

In this type of scheduling, next job to be done by the processor can be scheduled

before the current job completes. If a job of higher priority comes up, the processor

can be forced to release the current job and take up the next job. There are two

scheduling techniques that use pre-emptive scheduling –

Round robin scheduling − A small unit of time called time slice is defined

and each program gets only one time slice at a time. If it is not completed

during that time, it must join the job queue at the end and wait till all

programs have got one time slice. The advantage here is that all programs

get equal opportunity. The downside is that if a program completes

execution before the time slice is over, CPU is idle for the rest of the

duration.

Response ratio scheduling − Response ratio is defined as

ElapsedTimeExecutiontimereceivedElapsedTimeExecutiontimereceived

A job with shorter response time gets higher priority. So a larger program may

have to wait even if it was requested earlier than the shorter program. This

improves throughput of the CPU.

Non-preemptive Scheduling

In this type of scheduling, job scheduling decisions are taken only after the current

job completes. A job is never interrupted to give precedence to higher priority jobs.

Scheduling techniques that use non-preemptive scheduling are –

First come first serve scheduling − This is the simplest technique where

the first program to throw up a request is completed first.

Shortest job next scheduling − Here the job that needs least amount of time

for execution is scheduled next.

Deadline scheduling − The job with the earliest deadline is scheduled for

execution next.

Memory Management

Process of regulating computer memory and using optimization techniques to

enhance overall system performance is called memory management. Memory

space is very important in modern computing environment, so memory

management is an important role of operating systems.

As you know, computers have two types of memory – primary and secondary.

Primary memory is fast but expensive and secondary memory is cheap but

slower. OS has to strike a balance between the two to ensure that system

performance is not hurt due to very less primary memory or system costs do not

shoot up due to too much primary memory.

Input and output data, user instructions and data interim to program execution need

to be stored, accessed and retrieved efficiently for high system performance. Once

a program request is accepted, OS allocates it primary and secondary storage areas

as per requirement. Once execution is completed, the memory space allocated to it

is freed. OS uses many storage management techniques to keep a track of all

storage spaces that are allocated or free.

Contiguous Storage Allocation

This is the simplest storage space allocation technique where contiguous memory

locations are assigned to each program. OS has to estimate the amount of memory

required for the complete process before allocation.

Non-contiguous Storage Allocation

As the name suggests, program and associated data need not be stored in

contiguous locations. The program is divided into smaller components and each

component is stored in a separate location. A table keeps a record of where each

component of the program is stored. When the processor needs to access any

component, OS provides access using this allocation table.

In a real-life scenario primary memory space might not be sufficient to store the

whole program. In that case, OS takes the help of Virtual Storage technique,

where program is physically stored in secondary memory but appears to be stored

in primary memory. This introduces a miniscule time lag in accessing the program

components. There are two approaches to virtual storages –

Program paging − A program is broken down into fixed size pageand

stored in the secondary memory. The pages are given logical address or

virtual address from 0 to n. A page table maps the logical addresses to the

physical addresses, which is used to retrieve the pages when required.

Program segmentation − A program is broken down into logical units

called segments, assigned logical address from 0 to n and stored in

secondary memory. A segment table is used to load segments from

secondary memory to primary memory.

Operating systems typically use a combination of page and program segmentation

to optimize memory usage. A large program segment may be broken into pages or

more than one small segments may be stored as a single page.

File Management

Data and information is stored on computers in form of files. Managing file system

to enable users to keep their data safely and correctly is an important function of

operating systems. Managing file systems by OS is called file management. File

management is required to provide tools for these file related activities −

Creating new files for storing data

Updating

Sharing

Securing data through passwords and encryption

Recovery in case of system failure

Device Management

The process of implementation, operation and maintenance of a device by

operating system is called device management. Operating system uses a utility

software called device driver as interface to the device.

When many processes access the devices or request access to the devices, the OS

manages the devices in a way that efficiently shares the devices among all

processes. Processes access devices through system call interface, a programming

interface provided by the OS.

Security

Security module protects the resources and information of a computer system

against destruction and unauthorized access.

Command Interpretation

Command interpretation module takes care of interpreting user commands, and

directing system resources to process the commands. With this mode of interaction

with a system, users are not much concerned about hardware details of the system.

Types of Operating System

There are generally four types, categorized based on the types of computers they

control and the sort of applications they support. The categories are real-time

operating system, single user single task, and single user multitasking and multi-

user.

Real-Time Operating System (RTOS)

Real-time operating systems are used to control machinery, scientific instruments

and industrial systems such as embedded systems (programmable thermostats,

household appliance controllers), industrial robots, spacecraft, industrial control

(manufacturing, production, power generation, fabrication, and refining), and

scientific research equipment. A real time operating system typically has very little

user-interface capability, and no end-user utilities, since the system will be a

―sealed box‖ when delivered for use. A very important part of an RTOS is

managing the resources of the computer so that a particular operation executes in

precisely the same amount of time, every time it occurs. In a complex machine,

having a part move more quickly just because system resources are available may

be just as catastrophic as having it not move at all because the system is busy.

A RTOS facilitates the creation of a real-time system, but does not guarantee

the final result will be realtime; this requires correct development of the software.

A RTOS does not necessarily have high throughput; rather, an RTOS provides

facilities which, if used properly, guarantee deadlines can be met generally (soft

real-time) or deterministically (hard real-time). A RTOS will typically use

specialized scheduling algorithms in order to provide the real-time developer with

the tools necessary to produce deterministic behavior in the final system. A RTOS

is valued more for how quickly and/or predictably it can respond to a particular

event than for the given amount of work it can perform over time. Key factors in

an RTOS are therefore a minimal interrupt latency (the time between the

generation of an interrupt by a device and the servicing of the device which

generated the interrupt) and a minimal thread switching latency (the time needed

by the operating system to switch the CPU to another thread).

Single User, Single Task

The name implies, this operating system is designed to manage the computer so

that one user can effectively do one thing at a time. The palm OS for palm

handheld computers is a good example of a modern single-user, single-task

operating system.

Single User, Multitasking

This is the type of operating system most people use on their desktop and laptop

computers today. Microsoft's windows and Apple's Mac OS platforms are both

examples of operating systems that will let a single user have several programs in

operation at the same time. For example, it's entirely possible for a windows user

to be writing a note in a word processor while downloading a file from the Internet

while printing the text of an e-mail message.

Multi-user

Multi-user defines operating system or application software that allows concurrent

access by multiple users of a computer. A multi-user operating system allows

many different users to take advantage of the computer‘s resources simultaneously.

The operating system must make sure that the requirements of the various users are

balanced, and that each of the programs they are using has sufficient and separate

resources so that a problem with one user does not affect the entire community of

users. UNIX, VMS and mainframe operating systems, such as MVS, are examples

of multi-user operating systems. Time-sharing systems are multi-user systems.

Most batch processing systems for mainframe computers may also be considered

―multi-user‖, to avoid leaving the CPU idle while it waits for I/O operations to

complete.

Popular Operating Systems

Initially computers had no operating systems. Every program needed full

hardware specifications to run correctly as processor, memory and device

management had to be done by the programs themselves. However, as

sophisticated hardware and more complex application programs developed,

operating systems became essential. As personal computers became popular

among individuals and small businesses, demand for standard operating system

grew. Let us look at some of the currently popular operating systems −

Windows − Windows is a GUI operating system first developed by

Microsoft in 1985. The latest version of Windows is Windows 10.

Windows is used by almost 88% of PCs and laptops globally.

Linux − Linux is an open source operating system mostly used by

mainframes an supercomputers. Being open source means that its code is

available for free and anyone can develop a new OS based on it.

BOSS − Bharat Operating System Solutions is an Indian distribution of

Linux based on Debian, an OS. It is localized to enable use of local Indian

languages. BOSS consists of −

o Linux kernel

o Office application suite BharteeyaOO

o Web browser

o Email service Thunderbird

o Chat application Pidgim

o File sharing applications

o Multimedia applications

Mobile OS

An operating system for smart phones, tablets and other mobile devices is

called mobile OS. Some of the most popular OS for mobile devices includes−

Android − This Linux-based OS by Google is the most popular mobile OS

currently. Almost 85% of mobile devices use it.

Windows Phone 7 − It is the latest mobile OS developed by Microsoft.

Apple iOS − This mobile OS is an OS developed by Apple exclusively for

its own mobile devices like iPhone, iPad, etc.

Blackberry OS − This is the OS used by all blackberry mobile devices like

smart phones and playbooks.

Window Operating System

Windows 7

Windows 7 is an operating system that Microsoft has produced for use on personal

computers. It is the follow-up to the Windows Vista Operating System, which was

released in 2006. An operating system allows your computer to manage software

and perform essential tasks. It is also a Graphical User Interface (GUI) that allows

you to visually interact with your computer’s functions in a logical, fun, and easy

way.interact with your computer’s functions in a logical, fun, and easy way.*

The first screen appear after you turn on the power of computer is a desktop

• If it is a shared PC; more than one user use it, or one user with password

protected, you will arrive at Welcome Screen

or

1 - The Desktop

The Desktop is the main Windows 7 screen (see image below). It is the work area

where dialog boxes, windows, icons,and menus appear. Like an office desk, the

Windows 7 desktop contains items you can use to do your job. For instance, from

your desktop, you can perform file-management tasks and run software

applications. You can customize the appearance of the desktop to suit your

preferences.

Desktop Icons

The Desktop is where you’ll find icons (small pictures) for many of your most

frequently used programs. You’ll most likely see icons for Computer, Documents,

Recycle Bin, and Internet Explorer.

Computer – Allows you to see what drives are attached to your computer (for

example, your local hard disk drive, your CD/DVD drives, any networked shared

drives, and external drives, such as a USB flash drive). You can also view the files

that are located on these drives.

Documents– Supplies a ‘catch-all’ place for your personal files. Within here you

can see your files, any shared files from other computer users and any music or

pictures you may have stored. The Documents folder will sometimes be identified

by your name instead of the word “Documents.”

Recycle Bin– Stores any files you delete until you empty it.

Internet Explorer – Contains Windows’ built in web browser that integrates with

other Windows components (such as your folders and Documents).

The Desktop Components

The desktop for Windows 7 consists of two main components

1. Desktop that contains many components like icons "file, folder, shortcut. Etc…)

2. Task Bars

Desktop Components

1- Icons: An icon is a graphic image, a small picture or object that represents a

file, program, web page, or command. Icons help you execute commands, open

programs or documents quickly. To execute a command by using an icon, click or

double-click on the icon. It is also useful to recognize quickly an object in a

browser list. For example, all documents using the same extension have the same

icon.

We can classify icons as the following

• Folder Icons • File Icons • Shortcut Icons

Folder Icons File Icons Shortcut Icons

What is the difference between a file, a folder, and a shortcut?

All the data on your hard drive consists of files and folders. The basic difference

between the two is that files store data, while folders store files and other folders.

The folders, often referred to as directories, are used to organize files on your

computer. The folders themselves take up virtually no space on the hard drive.

Files, on the other hand, is a collection of data. stored in one unit, identified by a

filename. And filename period file extension can range from a few bytes to several

gigabytes. They can be documents, programs, libraries, and other compilations of

data. File name consists of two part name and extension

A shortcut is a link that points to a program on the computer. Shortcuts allow users

to create links to their programs in any folder, Start bar, Taskbar, Desktop or other

locations on their computer. A shortcut in Windows is commonly identified by a

small arrow in the bottom corner of the icon.

Special Icons on the desktop

• Recycle bin:

The Recycle Bin is a location (Folder) where deleted files are temporarily stored on

Microsoft Windows. The Recycling Bin allows users to recover files that have been

deleted in Windows.

• My Computer:

My Computer allows the user to explore the contents of their computer drives as

well as manage their computer files. Once My Computer is open you'll see all

available drives on your computer. For most users, you'll only be concerned with

the Local Disc (C:) drive, which is the hard drive and what stores all your files.

Icon Operations

• Arrange Icons On the Desktop

To change the arrangement of icons on the desktop do the following

1 - Right Click the desktop

2- Click Sort by

3- Select one of the 4 options to arrange icons from sub-menu

• View/Hide Icons

1- Right Click the desktop

2- 2- Click View

3- 3- Check to see if Auto Arrange has a check mark

4- 4- If it does uncheck it

• Change Icon size

1- Right Click the desktop

2- 2- Click View

3- 3- Show the required size

1- Right Click the desktop

2- Click View

3- Show the required size

• Auto Arrange Icon

1 - Right Click the desktop

2- Click View

3- Check to see if Auto Arrange has a check mark

4- If it does uncheck it

Start Menu Parts

The Start menu for Windows 7 consists of many Parts, to show Use the Start menu

to do these common activities:

• Start programs

• Open commonly used folders

• Search for files, folders, and programs

• Adjust computer settings

• Get help with the Windows operating system

• Turn off the computer

• Log off from Windows or switch to a different user account

Shutting Down the computer

At the bottom of the right pane is the Shut down button. Click the Shut down

button to turn off your computer. Clicking the arrow next to the Shut down button

displays a menu with additional options for switching users, logging off, restarting,

or shutting down.

• Switch user: If you have more than one user account on your computer,

Fast User Switching is an easy way for another person to log on to the

computer without logging you off or closing your programs and files.

• Log off: When you log off from Windows, all of the programs you were

using are closed, but the computer is not turned off.

• Lock: Locking your PC is a good option if you’ll be back soon. You'll

have to enter your password when you come back, which helps keep your

work more secure.

• Restart: The Restart button "reboots" your computer (it is sometimes

called a "warm boot" or "soft boot.") That means it saves your information

to the hard drive, turns off the computer for a moment, and then turns it back

on again.

• Sleep: Clicking on Sleep puts your computer in a low-power state, but

doesn't turn it off. The main advantage is that it allows you to get back to

work quickly, without having to wait for the computer to do a full reboot

Working with Windows

Whenever you open a program, file, or fo lder, it appears on your screen in a box or

frame called a window (that's where the Windows operating system gets its name).

Because windows are everywhere in Windows, it's important to understand how to

move them, change their size, or just make them go away. Parts of a window

Although the contents of every window are different, all windows share some

things in common. For one thing, windows always appear on the desktop - the main

work area of your screen. In addition, most windows have the same basic parts.

• Title bar. Displays the name of the document and program (or the folder

name if you're working in a folder).

•Minimize, Maximize, and Close buttons. These buttons hide the window,

enlarge it to fill the whole screen, and close it, respectively (more details on

these shortly).

• Menu bar. Contains items that you can click to make choices in a

program.

• Scroll bar. Let’s you scroll the contents of the window to see information

that is currently out of view.

• Borders and corners. You can drag these with your mouse pointer to

change the size of the window.

Moving a window

To move a window, point to its title bar with the mouse pointer . Then drag the

window to the location that you want. (Dragging means pointing to an item,

holding down the mouse button, moving the item with the pointer, and then

releasing the mouse button.)

Changing the size of a window

• To make a window fill the entire screen, click its Maximize button or double-

click the window's title bar.

• To return a maximized window to its former size, click its Restore button of the

Maximize button). Or, double-click the window's title bar. • To resize a window

(make it smaller or bigger), point to any of the window's borders or corners. When

the mouse pointer changes to a two headed arrow (see picture below), drag the

border or corner to shrink or enlarge the window.

• A window that is maximized cannot be resized. You must restore it to its

previous size first.

Hiding a window

• Hiding a window is called minimizing it. If you want to get a window out of the

way temporarily without closing it, minimize it.

• To minimize a window, click its Minimize button. The window disappears from

the desktop and is visible only as a button on the taskbar, the long horizontal bar at

the bottom of your screen.

• To make a minimized window appear again on the desktop, click its taskbar

button. The window appears exactly as it did before you minimized it.

Closing a window

• Closing a window removes it from the desktop and taskbar. If you're done with a

program or document and don't need to return to it right away, close it.

• To close a window, click its Close button

• If you close a document without saving any changes you made, a message

appears that gives you the option to save your changes.

Switching between windows

If you open more than one program or document, your desktop can quickly

become cluttered with windows. Keeping track of which windows you have open

isn’t always easy, because some windows might partially or completely cover

others.

Using the taskbar.

The taskbar provides a way to organize all of your windows. Each window has a

corresponding button on the taskbar. To switch to another window, just click its

taskbar button. The window appears in front of all other windows, becoming the

active window—the one you're currently working in.

To easily identify a window, point to its taskbar button. When you point to a

taskbar button, you'll see a thumbnail-sized preview of the window, whether the

content of the window is a document, a photo, or even a running video. This

preview is especially useful if you can't identify a window by its title alone.

• Using Alt +Tab. You can switch to the previous window by pressing

Alt+Tab, or cycle through all open windows and the desktop by holding

down Alt and repeatedly pressing Tab. Release Alt to show the selected

window.

• Using Aero Flip 3D. Aero Flip 3D arranges your windows in a

threedimensional stack that you can quickly flip through. To use Flip 3D:

• Hold down the Windows logo key & and press Tab to open Flip 3D.

Dialog boxes

A dialog box is a special type of window that asks you a question, allows you to

select options to perform a task, or provides you with information. You'll often see

dialog boxes when a program or Windows needs a response from you before it can

continue.

Unlike regular windows, most dialog boxes can't be maximized, minimized, or

resized. They can, however, be moved.

Understanding the parts of a window

When you open a folder or library, you see it in a window. The various parts of this

window are designed to help you navigate around Windows or work with files,

folders, and libraries more easily. Here's a typical window and each of its parts:

Window part What it's useful for

Navigation pane: Use the navigation pane to access libraries, folders, saved

searches, and even entire hard disks. Use the Favorites section to open your most

commonly used folders and searches; use the Libraries section to access your

libraries. You can also expand Computer to browse folders and subfolders.

Back and Forward buttons: Use the Back button and the Forward button to

navigate to other folders or libraries you've already opened without closing the

current window. These buttons work together with the address bar; after you use

the address bar to change folders.

Toolbar: Use the toolbar to perform common tasks, such as changing the

appearance of your files and folders, burning files to a CD, or starting a digital

picture slide show. The toolbar's buttons change to show only the tasks that are

relevant.

Address bar: Use the address bar to navigate to a different folder or library or to

go back to a previous one. Library pane The library pane appears only when you

are in a library (such as the Documents library). Use the library pane to customize

the library or to arrange the files by different properties.

Column headings: Use the column headings to change how the files in the file list

are organized. For example, you can click the left side of a column heading to

change the order the files and folders are displayed in, or you can click the right

side to filter the files in different ways. (Note that column headings are available

only in Details view.

File list: This is where the contents of the current folder or library are displayed. If

you type in the search box to find a file, only the files that match your current view

(including files in subfolders) will appear.

Search box: Type a word or phrase in the search box to look for an item in the

current folder or library. The search begins as soon as you begin typing—so if you

type "B," for example, all the files with names starting with the letter B will appear

in the file list.

Details pane Use the details pane to see the most common properties associated

with the selected file. File properties are information about a file, such as the

author, the date you last changed the file, and any descriptive tags you might have

added to the file.

Preview pane: Use the preview pane to see the contents of most files. If you select

an e-mail message, text file, or picture, for example, you can see its contents

without opening it in a program. If you don't see the preview pane, click the

Preview pane button in the toolbar to turn it on.

Viewing and arranging files and folders

When you open a folder or library, you can change how the files look in the

window. For example, you might prefer larger (or smaller) icons or a view that lets

you see different kinds of information about each file. To make these kinds of

changes, use the Views button in the toolbar.

Each time you click the left side of the Views button, it changes the way your files

and folders are displayed by cycling through five different views: Large Icons,

List, a view called Details that shows several columns of information about the

file, a smaller icon view called Tiles, and a view called Content that shows some of

the content from within the file.

If you click the arrow on the right side of the Views button, you have more

choices. Move the slider up or down to fine tune the size of the file and folder

icons. You can see the icons change size as you move the slider.

Working with file and folder

1. Selecting • Single object

To select a single object, click on it once.

• |Multiple object

There are several ways to select Multiple files or folders.

• To select a consecutive group of files or folders, click the first item, press

and hold down the Shift key, and then click the last item.

• To select Multiple files or folders that are near each other, drag the mouse

pointer to create a selection around the outside of all the items that you want

to include.

• To select non-consecutive files or folders, press and hold down the Ctrl

key, and then click each item that you want to select.

• To select all of the files or folders in a window, on the toolbar, click

Organize, and then click Select all. If you want to exclude one or more

items from your selection, press and hold down the Ctrl key, and then click

the items.

Notes: After selecting files or folders, you can perform many common tasks,

such as copying, deleting, renaming, printing, and compressing. Simply

right-click the selected items, and then click the appropriate choice.

2. Rename

• Click the file or folder to select it.

• Click the organize button on the toolbar, and then click Rename.

• With the name selected highlights, type a new name, or click to position

the insertion point, and then edit the name.

• Press Enter

Notes:

• Right-click the file or folder you want to rename, click Rename, type a

name, and then press Enter.

• You can also select the file, then press F2, type a name, and then press

Enter.

• File names can be up to 255 characters. You can use spaces and

underscores in names, but you can’t use the following characters: * : < > | ?

“ \ or /. Remember the best way to keep your files organized is with a

consistent naming convention.

3. Copying

When you copy an item, the original item remains in its original location—

plus you have the new copy

• Open the location that contains the file you want to copy.

• Right-click the file, and then click Copy.

• Open the location where you want to store the copy.

• Right-click an empty space within the location, and then click Paste. The

copy of the original file is now stored in the new location.

Notes:

• Another way to copy and paste files is to use the keyboard shortcuts

Ctrl+C (Copy) and Ctrl+V (Paste).

• You can also press and hold the right-mouse button and then drag the file

to the new location. When you release the mouse button, click Copy here.

4. Moving (cut)

Moving a file (or folder) is different from copying it. Moving cuts the item

from its previous location and places it in a new location. Copying leaves the

original item where it was and creates a copy of the item elsewhere. In other

words, when you copy something you end up with two of it. When you

move something, you only have the one thing.

• Open the drive or folder containing the file or folder you want to move.

• Select the files or folders you want to move.

• Click the Organize button on the toolbar, and then click Cut.

• Display the destination folder where you want to move the files or folder.

• Click the Organize button on the toolbar, and then click Paste.

Copy or Move a File or Folder Using Drag and Drop

• Open the drive or folder containing the file or folder you want to copy or

move.

• Select the files or folders you want to copy or move.

• In the Navigation pane, point to a folder list to display the expand and

collapse arrows.

• Click the arrows to display the destination folder, and then click the

destination folder.

• Right-click the selected files or folders, drag to the destination folder, and

then click Copy Here or Move Here.

Notes:

To move the selected items, drag them to the destination folder. To copy the

items, hold down the Ctrl key while you drag.

Another way to copy and paste files is to use the keyboard shortcuts Ctrl+X

(Cut) and Ctrl+V (Paste). Pay attention to pop-up messages that appear

when dragging—you can use these to find out what will happen when you

release the mouse button.

5. Create a Folder

• Open the drive or folder where you want to create a folder.

• Click the New folder button on the toolbar.

• With the New Folder name selected, type a new name.

• Press Enter.

Notes:

Right-click a blank area on the desktop or in the folder window, point to New, and

then click Folder.

6. Deleting

• Select the file or folder.

• Click the Organize button and select Delete from the pull-down menu.

• After you select delete a confirmation message appears.

Notes:

• You can also delete a file or folder by press right click on the item and then

click delete.

• Or press Del buttons on the keyboard.

• The easiest way to delete on the desktop by drag and drop it to recycle Bin.

• When you delete a file or folder from your hard disk, it's not deleted right

away. Instead, it's stored in the Recycle Bin until the Recycle Bin is emptied.

• If you delete a file or folder from a network folder or from a USB flash

drive, it might be

permanently deleted rather than being stored in the Recycle Bin.

• If a file cant be deleted, it might be in use by a program that's currently

running. Try closing the program or restarting your computer to fix the

problem. For more information.

Note: To permanently delete a file without first moving it to the Recycle Bin, select

the file, and then press Shift + Delete.

Permanently delete files from the Recycle Bin

• When you delete a file, it's usually moved to the Recycle Bin so that you

can restore the file later if necessary.

• To permanently remove files from your computer and reclaim any hard

disk space they were using, you need to delete the files from the Recycle

Bin. You can delete individual files from the Recycle Bin or empty the

entire Recycle Bin at once.

1. Open the Recycle Bin by double-clicking the Recycle Bin on the desktop.

2. Do one of the following:

• To permanently delete one file, click it, press Delete, and then click Yes.

• To delete all of the files, on the toolbar, click Empty the Recycle Bin, and

then click Yes.

Notes:

• You can empty the Recycle Bin without i ￡ Empty Recycle Bin opening it

by right-clicking the Recycle Bin and then clicking Empty Recycle Bin. •

You can permanently delete a file from your computer without sending it to

the Recycle Bin by clicking the file and then pressing Shift + Delete.

Restore item from recycle Bin

• Open the Recycle Bin by double-clicking the Recycle Bin on the desktop.

• Do one of the following:

• To restore a file, click it, and then, on the toolbar, click Restore this item.

• To restore all of the files, make sure that no files are selected, and then, on

the toolbar, click Restore all items.

• The files will be restored to their original locations on your computer.

7. Opening an existing file or folder

• To open a file, double-click it. The file will usually open in the program

that you used to create or change it. For example, a text file will open in

your word-processing program.

8. Search for a file and folder

Windows provides several ways to find files and folders. There isn't one best

way to search—you can use different methods for different situations.

A. Use the search box on the Start menu

You can use the search box on the Start menu to find files, folders, programs, and

e-mail messages Stored on your computer.

• Click the Start button and then type a word or part of a word in

the search box.

• Search result appear as soon as you start typing in the search box.

as you start typing in the search box. As you type, items that match your text will

appear on the Start menu. The search results are based on text in the file name, text

in the file, tags, and other file properties.

B. Use the search box in a folder or library

Browsing for the file might mean looking through hundreds of files and subfolders.

To save time and effort, use the search box at the top of the open window.

The search box filters the current view based on text that you type. The search

looks for text in the file name and contents; and in the file properties, such as in

tags. In a library, the search includes all folders included in the library as well as

subfolders within those folders. To search for a file or folder by using the search

box:

• Type a word or part of a word in the search box.

• As you type, the contents of the folder or library are filtered to reflect each

successive character you type. When you see the file that you want, stop

typing.

For example, now, suppose that you're looking for your invoice files, so you type

"invoice11 in the search box. As you type, the view is automatically filtered and

you see something like this:

Notes:

• You can use a question mark (?) as a wildcard for a single character and

an asterisk (*) as a wildcard for any number of characters.

• The easiest way to start search window is by press F3

• I f you know which file type it is, you can just enter the file extension

("JPG" for example) in the search box.

• You can also use other techniques in the search box to quickly narrow

down a search. For example, if you're searching for a file based on one or

more if its properties (such as a tag or the date the file was last modified),

you can use search filters to specify the property in your search. Or, you can

type keywords in the search box to narrow down your results even further.

Working with Control Panel

You can use Control Panel to change settings for Windows. These settings control

nearly everything about how Windows looks and works, and you can use them to

set up Windows so that it's just right for you.

• Open Control Panel by clicking the Start button and then clicking

Control Panel.

• You can display Control Panel screen with different view types as follow

Open control Panel by

There are two ways to find Control Panel items: o Use search: To find a setting

you're interested in or a task you want to perform, type a word or phrase in the

search box. For example, type "sound" to find specific settings for your sound card,

system sounds, and the volume icon on the taskbar. o Browse: you can explore

Control Panel by clicking different categories (for example, System and Security,

Programs, or Ease of Access), and viewing common tasks listed under each

category or, under View by, click either Large icons or Small icons to view a list

of all Control Panel items.

• The following table gives you a description of all the Control Panel

categories, including the various programs you can find by clicking each

category’s hyperlink*.

Category Name . . . To Display These Groups of Links

System and Security Action Center, Windows Firewall, System, Windows Update, Power

Options, Backup and Restore, BitLocker Drive Encryption, and Administrative Tools

User Accounts User Accounts, Windows Cardspace, Credential Manager, and Mail (32-bit)

Network and Internet

Network and Sharing Center,

Homegroup, and Internet Options

Appearance and Personalization Personalization, Display, Desktop Gadgets, Taskbar and Start Menu, Ease

of Access Center, Folder Options, and Fonts

Hardware and Sound Devices and Printers, AutoPlay, Sound,

Power Options, Display, and Windows Mobility

Center

Clock, Language, and Region Date and Time, and Region and Language

Programs Programs and Features, Default

Programs, and Desktop Gadgets

Ease of Access Ease of Access Center and Speech Recognition

Change desktop background (wallpaper)

Your desktop background (also called wallpaper) can be a digital picture from your

personal collection or one that comes with Windows. You can also select a color

for your desktop background or use a color to frame your background picture.

Windows comes with lots of desktop background choices.

• To change the desktop background

1. Open Desktop Background by clicking the Start button, clicking Control

Panel, clicking Appearance and Personalization, clicking Personalization, and

then clicking Desktop Background.

2. Click the picture or color you want for your desktop beck ground. If the picture

you want to use is not in the list of desktop background pictures, click the Picture

location down arrow to view other categories, or click Browse to search for the

picture on your computer. When you find the picture you want, double-click it. It

will become your desktop background and appear in the list of desktop

backgrounds.

3. Under How should the picture be positioned, choose to have the picture fit the

screen, tile, or be centered on the screen, and then click OK.

Note: You can make any picture stored on your computer (or a picture you are

currently viewing) your desktop background by rightclicking the picture, and then

clicking Set as Desktop Background.

Change screen saver

Windows comes with several screen savers. You can also create your own screen

savers from personal pictures you've saved on your computer, or some software

companies might develop additional screen savers for download or purchase.

To change a screen saver

1. Open Screen Saver Settings by clicking the Start button, clicking

Control Panel, clicking Appearance and Personalization, clicking

Personalization, and then clicking Screen Saver.

2. Under Screen saver, in the drop-down list, click the screen saver you

want to use.

3. Click Preview to see what your chosen screen saver will look like.

4. Click OK.

Note:

• To clear a screen saver, move your mouse or press any key.

• You can change wallpaper and screen saver by right click on the desktop

and then choose personalize

How to use the taskbar

You can customize the taskbar, including the way taskbar buttons look, how they

group together when you have more than one window open, change where the

taskbar is on your desktop, and decide what icons and apps are on it.

Linux/Unix Operating System

Classification of UNIX/Linux

UNIX is a Multi-User/Multi-Tasking operating system and exists in many

different versions (“derivates”): Solaris, AIX, XENIX, HP-UX, SINIX, Linux.

Operating system (OS): Sum of all programs which are required to operate a

computer and which control and monitor the application programs.

Essential features UNIX

• has been originally written in the programming language C, and is therefore a

classical platform for C-programs. UNIX contains well suited environments

for program development (C, C++, Java, Fortran, ...).

• is mainly used for scientific-technical applications on mainframes and

workstations, but has become, because of Linux, also popular for classical PC-

applications throughout the last years.

• is perfectly suited for application in networks. Larger systems and networks

require an administrator.

• offers various alternatives for the solution of most tasks. The multitude of

commands (more than in any other OS) are brief and flexible.

• is originally command-line oriented, but can be used via a graphical user

interface (X Window system).

Linux is available (also via internet) in different distributions (S.u.S.E., Fedora,

Debian etc.). Meanwhile there is a variety of direct-start (live) systems, which can

be started, without installation, directly from CD or other bootable storage devices

(Knoppix, Ubuntu, . . . ). There are also interesting “mini versions” (<100 MB)

designed for a start from USBsticks (e.g., Puppy). The source code of Linux is

free.

2 First steps at the computer

User, logon, logoff

Since UNIX is a multi-user operating system, it can deal with several users

simultaneously. Each user needs a user account.

Each user has a personal environment (home directory, shell), which can be

accessed only by her-/himself (and by the system administrator and those people

who know the password – legitimate or by hacking).

Inside the system the user is identified by his user ID (UID) and his group identity

(group ID, GID).

There are two user types:

• ‘normal’ users with restricted rights and the

• system administrator (root) with all privileges.

The latter is responsible for the installation, configuration and maintenance of the

system as well as the user administration.

Each user has to logon and to logoff from the system (login/logout). Each user

account is protected by a password.

Graphical user interface

Originally, UNIX is command-line oriented. The X Window system enables

convenient interaction via a window-oriented graphical interface, similar to other

OS. The window manager is responsible for the management and display of the

individual windows. Each window manager (and there are a variety of such

managers) can be distinguished by its own Look and Feel (appearance of window

decorations and control devices etc.). Most window managers can be chosen at the

login-menu.

Examples for simple window managers:

• twm: very simple and resource-saving

• mwm: Motif window manager, more common and more advanced

• xfce: convenient, simple, and resource-saving (recommended for use in virtual

machines)

Moreover, almost all Linux distributions provide graphical desktop environments

such as KDE or GNOME, which have a functionality far beyond simple window

managers.

command xterm

Syntax:

xterm [options]

Though there is a graphical interface, UNIX needs the possibility for direct

command input for practical use. Therefore, at least one terminal window needs to

be open. This can be accomplished via the window manager or the desktop

environment (‘console’)

More windows can then be opened with the command xterm.

Generally, all UNIX commands have a variety of options, which usually begin

with -. For the commands which will be introduced in the fo llowing, we will

provide only the most important ones.

Example:

wegner@arber:~ > xterm -geo 80x40 -fn 10x20

The command xterm is called with two options -geo, -fn, which, in this case, need

additional arguments (width and height of window, font name & size).

command man

Syntax:

man command

man -k expression

Displays the manual pages (“man pages”) for the provided command. man -k

searches for man pages containing the expression in the NAME section. A man

page usually consists of the following sections

• NAME command and purpose

• SYNOPSIS syntax of command

• DESCRIPTION of command effect

• FILES which are modified and/or needed

• OPTIONS if present

• EXAMPLE(S) for application (rarely)

• BUGS errors, if known

• SEE ALSO other commands in the same context

command passwd

Syntax:

Passwd

sets a new password.

Passwords should be constructed from a combination of letters, digits and special

characters, and should not appear in any dictionary or similar list. Otherwise, the

password can be hacked by systematic search algorithms.

The command to set/change the password and the required conventions (length,

number of digits/letters/special characters) can vary from system to system. The

following example is a common one, e.g., valid for the workstations at the CIP

Pool (but not for the workstations of the USM).

Example:

wegner@arber: ~ > passwd

Changing password for wegner

Old password: myoldpasswd

Enter the new password (minimum of 5, maximum of 8 characters)

Please use a combination of upper and lower case letters and numbers.

New password: mynewpasswd

Re-enter new password: mynewpasswd

Password changed.

Command who, whoami

Syntax:

who

whoami

who displays information about all users which are logged into the system

• user name,

• terminal where the corresponding user is working,

• time of login.

whoami is self-explanatory.

Example:

wegner@arber:~ > whoami

arber!wegner pts/5 Oct 20 12:45

Working at external terminals

To login to a distant host, one has to provide the corresponding IP address, either

numerical or as the complete host name name.domain. In local networks (CIP-

Pool), the brief host name (without domain) is sufficient. To establish the

connection and to encrypt the transmitted data, one should use exclusively the so-

called “secure” commands. Avoid ftp and use sftp instead. With ftp, even the

password is not encoded!

command ssh

Syntax:

ssh (-4) -X -l username hostname

ssh (-4) -X username@hostname

Enables logging in to an arbitrary host which can be located via an IP address (if

one knows the user account and the password). Logoff with exit, Ctrl-D or logout.

In case, the option -4 (without brackets) forces an IPv4 connection (if IPv6 is not

working)

Example:

wegner@arber:~ > ssh -X -l wegner lxsrv1.lrz-muenchen.de

Password: mypasswd

Last login: Sun Oct 22 ...

*********************

Mitteilungen

*********************

wegner@lxsrv1:~ > logout

Connection to lxsrv1.lrz-muenchen.de closed.

OR (if connection within “own” cluster)

Example:

wegner@arber:~ > ssh -X wegner@arber

Last login: Sun Oct 22 ...

etc. (keine Passwort-Abfrage)

An additional advantage of the secure shell is that the distant host hostname can

display X applications on the local terminal, without requiring the command xhost

(as in earlier times). For certain hosts, the command ssh requires the option -X to

enable this feature.

command scp

To copy files from one host to another, the command scp (“secure copy”) is used,

see also cp.

Syntax:

scp (-4) file1 username@hostname:file2

scp (-4) username@hostname:file1 file2

The first command copies the local file file1 to the external host under name file2,

the second command vice versa. Note the colon! scp -r enables to copy complete

directories recursively, compare cp -r.

3 File systems

Logics, file types

“In UNIX everything is a file.”The following file-system objects can be found

• ‘normal’ (text-) files

• executable files (binary files or shell scripts)

• directories

• device files

• pipes

• symbolic or hard links (references to files)

All files and file system objects are ordered within a hierarchical file tree with

exactly one root directory ‘/’.

In contrast to the MS-Windows file system, the UNIX file system does not

distinguish between different drives. All physical devices (hard disks, DVD,

CDROM, USB, floppy) are denoted by specific files inside a certain directory

within the file tree (usually within /dev).

File names consist of a sequence of letters, digits and certain special characters,

and must not contain slashes (for convenience, they should neither contain empty

spaces).

Avoid characters which might be interpreted by the shell in a special way. A file

can be referenced within the file tree by either an absolute or a relative path name.

An absolute path name consists of all directories leading to the file and the file

name, and always begins with a / (the root directory).

In many shells and application programs, the tilde denotes the home directory.

command pwd

Syntax:

pwd

displays the current directory.

Example:

wegner@arber:~ > pwd

/home/wegner

wegner@arber:~ >

command cd

Syntax:

cd [directory]

Changes into the given directory, or into the home directory when no parameter is

provided. As in MS-DOS/Windows, “..” denotes the parent and “.” the current

directory.

Example:

wegner@arber:~ > cd /home/puls

wegner@arber:/home/puls > pwd

/home/puls

wegner@arber:/home/puls > cd ..

wegner@arber:/home > pwd

/home

wegner@arber:/home > cd

wegner@arber:~ > pwd

/home/wegner

wegner@arber:~ >

Search pattern for file names

In principle, the shell is a specific program which deals with the interpretation of

input commands. If these commands have parameters which are file names, several

files can be addressed simultaneously by means of a search pattern, which is

expanded by the shell. In any case, the file name expansion is performed prior to

the execution of the command.

expression meaning

* ‘almost’ arbitrary (incl. empty) string of characters

? a single ‘almost’ arbitrary character

[...] a range of characters

[!...] a negated range of characters

‘almost’ arbitrary: leading dot (e.g., hidden files, ../ etc.) excluded

command ls

Syntax:

ls [-alR] [file/directory]

displays the names (and, optionally, the properties) of files or lists the content of a

directory. File and directory names can be be absolute or relative.

Important options

-a list also files/directories which begin with a dot (hidden)

-l long listing format. Displays permissions, user and group, time stamp,

size, etc.

-R for directories, all sub-directories will be displayed recursively.

Example:

wegner@arber:~ > ls

hello* hello.cpp hello.f90 nsmail/

wegner@arber:~ > ls -a

./ .bash_history .netscape/ hello.cpp

../ .bashrc* .ssh/ hello.f90

.Xauthority .history hello* nsmail/

wegner@arber:~ > ls /var/X11R6

app-defaults/ bin/ lib@ sax/

scores/ xfine/ xkb/

wegner@arber:~ > ls .b*

.bash_history .bashrc*

wegner@arber:~ > ls [a-h]*

hello* hello.cpp hello.f90

wegner@arber:~ > ls *.?[9p]?

hello.cpp hello.f90

wegner@arber:~ >

Copy, move and delete files/directories

In addition to ls there are other commands for working with files which can be

used together with file name patterns.

command mkdir, rmdir

Syntax:

mkdir directory

rmdir directory

mkdir creates an empty directory, rmdir deletes an empty directory.

Example:

wegner@arber:~ > ls

hello* hello.cpp hello.f90 nsmail/

wegner@arber:~ > mkdir numerik

wegner@arber:~ > ls

hello* hello.cpp hello.f90 nsmail/ numerik/

wegner@arber:~ > rmdir numerik

wegner@arber:~ > ls

hello* hello.cpp hello.f90 nsmail/

wegner@arber:~ >

command cp

Syntax:

cp file1 file2

cp file1 [file2 ...] directory

cp -r dir1 dir2

cp -r dir1 [dir2 ...] directory

copies files or directories. The original file/directory remains unmodified.

option:

-r directories are copied recursively with all subdirectories.

Several possibilities:

cp file1 file2

file1 is copied to file2. Attention: if file2 already exists, it is overwritten (mostly

without warning), and the original file2 is lost!!!

cp file1 [file2 file3] dir

If dir exists, file1 [, file2, file3] are copied into dir. If dir does not exist, you get

an error warning (for more than two arguments), or, for two arguments, dir is

interpreted as a file name and file1 is copied to a file named dir.

cp -r dir1 dir2

If dir2 already exists, dir1 is recursively copied into dir2. If dir2 does not exist, a

recursive copy of dir1 is created and named dir2.

cp -r dir1 dir2 dir3 dir4

If dir4 already exists, dir1, dir2, dir3 are copied into dir4. If dir4 does not exist,

you get an error warning, as well as for other combinations of files and directories

within the command.

Example:

wegner@arber:~ > ls

hello* hello.cpp hello.f90 nsmail/ numerik/

wegner@arber:~ > cp hello.cpp hello2.cpp

wegner@arber:~ > ls

hello* hello.f90 nsmail/

hello.cpp hello2.cpp numerik/

wegner@arber:~ > cp hello.cpp numerik

wegner@arber:~ > ls numerik

hello.cpp

wegner@arber:~ >

command mv

Syntax:

mv file1 file2

mv file1 [file2 ...] directory

mv dir1 dir2

mv dir1 [dir2 ...] directory

Rename or move files or directories. Similar to cp, but original is ‘destroyed’.

First command from above renames files, other commands move files/directories.

(Actually, only the pointer in the ‘inode table’ is changed, but there is no physical

move – except if you move the file to another file system).

Note: no option [-r] required

Several possibilities, analogue to cp.

Example:

wegner@arber:~ > ls

hello* hello.f90 nsmail/

hello.cpp hello2.cpp numerik/

wegner@arber:~ > mv hello2.cpp hello3.cpp

wegner@arber:~ > ls

hello* hello.f90 nsmail/

hello.cpp hello3.cpp numerik/

wegner@arber:~ > ls numerik

hello.cpp

wegner@arber:~ > mv hello3.cpp numerik

wegner@arber:~ > ls

hello* hello.cpp hello.f90 nsmail/ numerik/

wegner@arber:~ > ls numerik

hello.cpp hello3.cpp

wegner@arber:~ >

command rm

Syntax:

rm [-irf] file(s)/directory(ies)

Delete files and/or directories. After deleting, the deleted files cannot be

recovered! Use rm only with greatest caution. E.g., the command rm -r * deletes

recursively (in most cases without further inquiry) the complete file tree below the

current directory (leaving the hidden files/directories beginning with . though).

Options:

-i delete only after confirmation

-r directories will be recursively deleted (with all subdirectories)

-f force: suppress all safety inquiries.

Note: Varying from system to system, rm without the option -f might need a

confirmation or not (the latter is the standard).

Example:

wegner@arber:~/numerik > ls

hello.cpp hello3.cpp

wegner@arber:~/numerik > rm -i hello3.cpp

rm: remove ‘hello3.cpp’? y

wegner@arber:~/numerik > ls

hello.cpp

wegner@arber:~/numerik >

File permissions/Access rights

The UNIX file system distinguishes between three different access rights or file

mode bits. (Note: actually, there are more access rights, but these are of interest

only for administrators.)

r read: permits the reading of file contents, or, for directories, the listing of their

content.

w write: permits the modification of files (incl. delete). To create or delete files,

the parent directory(ies) need write access as well!

x execute: permits the execution of binary files (commands, programs) and of

shell scripts from the command line. For directories, the x bit is required to change

into this directory and to access the files/directories inside.

Access rights are individually defined for

u the owner of the object

g the group to which the object belongs

o all other users

a all users (i.e., u + g + o)

The access rights of a file can be changed by means of the command chmod.

command chmod

Syntax:

chmod [ugoa][+-=][rwx] file(s)/directory(ies)

Change the access rights of files or directories. These rights are displayed by ls -l

according to the pattern

uuugggooo

rwxrwxrwx

Example:

wegner@arber:~/numerik > ls -l

total 4

-rw-r--r-- 1 wegner stud 100 Oct 20 15:02 hello.cpp

wegner@arber:~/numerik > chmod go+w hello.cpp

wegner@arber:~/numerik > ls -l

total 4

-rw-rw-rw- 1 wegner stud 100 Oct 20 15:02 hello.cpp

wegner@arber:~/numerik >

4 Editing and printing text files

To modify (= edit) the content of a text file, an editor is needed. Within UNIX

there is a variety of editors, which can be distinguished mostly with respect to

ease of use and memory requirements.

The editor vi and vim

vi is the only editor which is present on all UNIX systems. The editor vi

• can be completely keyboard controlled

• is extremely flexible

• rather difficult to learn

vim is a derivate from vi, and can be controlled also by the mouse.

Those of you who enjoy a challenge should learn using this editor.

A somewhat simpler and more convenient alternative, which is also implemented

in (almost) all UNIX systems,is

The editor emacs

The editor emacs works in an own window, and can be controlled (in addition to

keys) by menus and mouse. emacs has rather large memory requirements (no

problem for today’s computers), since this ‘editor’ can do much more than only

editing.

More important commands

a2ps converts ASCII text to PostScript. Often required to print text under Linux.

a2ps [options] textfile

-1, -2, ..., -9 predefined font size and page layout.

E.g., with -2 two pages of text are displayed side-by-side on one

output page.

-o output file (*.ps)

-P NAME send output to printer NAME

diff file1 file2 compares two files. If they are identical, no output.

touch file sets the current time stamp for a file. Can be used to create an empty

file. finger account displays additional information for the

user of a certain account (name of user, project, etc.)

gv datei.ps displays PostScript files and files of related formats (e.g., *.eps, *.pdf).

acroread file.pdf displays pdf files and allows for simple manipulations (e.g., copy

text or figures to the clipboard).

gimp file starts the image manipulation program gimp (similar to photoshop).

Allows to view, manipulate and print image files (e.g., *.jpg, *.tif, *.png).

ps2pdf file.ps converts ps-files to pdf-files. The file file.pdf will be automatically

created.

gzip file. Compresses file via Lempel-Ziv algorithm. The file file.gz is created and

the file file deleted. Typical compression factor 3.

gunzip file.gz. Corresponding decompression.

tar “tape archive”. Nowadays mainly used to create one single file from a file tree,

which then, e.g., can be sent by email. Reverse process also with tar.

tar -cvf direc.tar direc creates (c) file (f) direc.tar from directory direc. Verbose

progress is displayed (v).

tar -xvf direc.tar re-creates original file tree under original name (./direc).

tar -zcvf direc.tgz direc

tar -zxvf direc.tgz additional compression/dekompression via gzip.

Note: This command is extremely ‘powerful’. Either read the man pages, or use

the command as given.