open source magazine

Fiat Lux! 02/2010

This article is subject to creative commons licensing (http://creativecommons.org/licenses/by/3.0/)

Fiat Lux! 02/2010

Welcome to the first Fiat Lux!

The Editor

Here begins the first edition of Fiat Lux, the magazine of

the Free Software Cell of Government Engineering

College, Bartonhill. Like all Free Software projects this

magazine has been a labor of collaboration and it would

continue to remain so. All articles were provided

voluntarily by our members. In fact we've received more

articles than our modest page limit of 20 would allow

(they will be in the next issue). If you have an article

relevant to this magazine be assured that it has a spot in

here.

Before going into further details about this magazine lets

demystify what this Free Software Cell really is. The

Free Software Cell of our college is a volunteer

organization with members from all branches and all

semesters. As it is clear from the name, we are all about

Free/Open Source Software (FOSS) . If you are

wondering how to join the Cell you'll be happy to know

that if you show up at any of our meetings you are one of

us :-)

The goal of this magazine is to provide a platform for

Free/Open Source enthusiasts to learn from one

another. The magazine hopes to provide content

relevant to the scope of our various branches. Our

working philosophy is that everyone of us has something

to teach and something to learn from one another . This

issue has been intended as a basic stepping stone into

the various goings on in the world of FOSS. So if you

were expecting a bit more, kindly be patient, you'll get

what you are looking for in a later issue. Let us remind

you once again that this is a collaborative work,

feedback is always welcome.

WE would like to mention all those who have helped,

participated and guided this small endeavor. First and

foremost thanks goes to Renjith Sir ( Mr. Renjith S

Kumar, Lecturer, ME ), who is the guide and guardian of

the FOSS cell. Further thanks goes to our Principal Dr.

Geetha K. P. for giving us permission and support to

start this magazine. Further, I'd like to thank all the

members of the cell for the passion and commitment

they have shown in their contributions in all stages from

planning to design.

We're waiting for your criticisms, and hopefully some

complements :-)


Fiat Lux! 02/2010

What it means to be free

Vidya S

Vani S Krishna

Most software that you buy or download comes in the compiled

ready-to-run version. ‘Compiled’ means that the actual program

code that the developer created, known as the source code,

has run through a special program called a compiler that

translates the source code into a form that the computer can

understand. It is extremely difficult to modify the compiled

version of most applications and nearly impossible to see

exactly how the developer created different parts of the

program. Most commercial software manufacturers see this as

an advantage that keeps other companies from copying their

code and using it.

Open source software is quite different. The source code is

included with the compiled version and modification or

customization is actually possible. The software developers who

support the open source concept believe that by allowing

access to the source code, the application will be more useful

and error-free over the long term.

It is a common mistake to think of open source and free

software as one and the same. The difference can be

summarized in statement “all free software is open source but

not all open source software is free software”. The term free

here is meant as a reference to freedom and not price. In fact

there are many proprietary software that are technically open

source (Java is a good example of this).

FREE SOFTWARE

Free software is a matter of the users' freedom to run, copy,

distribute, study, change and improve the software. More

precisely, it refers to four kinds of freedom, for the users of the

software

• The freedom to run the program, for any purpose

(freedom 0).

• The freedom to study how the program works, and

adapt it to your needs (freedom 1). Access to the

source code is a precondition for this.

• The freedom to redistribute copies so you can help

your neighbor (freedom 2).

• The freedom to improve the program, and release

your improvements to the public, so that the whole

community benefits (freedom 3). Access to the

source code is a precondition for this.

PROPRIETARY SOFTWARE

The term "proprietary software" is often used to mean computer

software which is not free. Terminology for forms of software

licensing is not fully standardized and can be controversial. A

literal meaning of "proprietary" in relation to software is that it

has a copyright owner who can exercise control over what users

can do with the software. However, the term is commonly used

in a narrower sense to describe software with restrictions on

use or private modification, or with restrictions judged to be

excessive on copying or publishing of modified or unmodified

versions. These restrictions are placed on it by one of its

proprietors. In this sense it is also known as "non-free software"

and is the opposite of free software, generally speaking.

A related term is closed-source software which usually

describes software whose source code is not published, in

contrast with "open source". While most proprietary software is

closed-source, source-available proprietary software also exists.

SHAREWARE AND FREEWARE

Shareware is software that is distributed free on a trial basis

with the understanding that the user may need or want to pay

for it later. Some software developers offer a shareware version

of their program with a built-in expiration date (after 30 days, the

user can no longer get access to the program). Other

shareware is offered with certain capabilities disabled as an

enticement to buy the complete version of the program.

Shareware is sometimes confused with freeware. Like free

software, freeware is free in the economic sense of the word but

like shareware, freeware program code is proprietary and the

creator retains the copyright. Like shareware, freeware is

software you can download, pass around, and distribute without

any initial payment. However, the great part about freeware is

that you never have to pay for it. No 30 day limit, no demo

versions, no disabled features it's totally free. Things like minor

program updates and small games are commonly distributed as

freeware. Though freeware does not cost anything, it is still

copyrighted, so other people can't market the software as their

own.

SOFTWARE LICENCE

We all click on that button that says “Accept” while installing a

software. It is actually something called an end user agreement

to which we have just agreed without even reading the

agreement. This agreement is a form of what is called a


Fiat Lux! 02/2010

software license. The license is a legally valid agreement that

the user of the software agrees to abide by.

You may now be thinking that a license is something that is

found in proprietary software alone. Actually all free software

comes with a license to which we have to agree. It may be any

one of the many licenses around.

CREATIVE COMMONS LICENSE

Creative Commons (CC) is a nonprofit organization

headquartered in San Francisco, California, United States

devoted to expanding the range of creative works available for

others to build upon legally and to share. The organization has

released several copyright licenses known as creative

commons licenses for free to the public. These licenses allow

creators to communicate which rights they reserve, and which

rights they waive for the benefit of recipients or other creators.

Wikipedia is one of the notable web-based projects using one of

its licenses.

BSD LICENSE

The BSD license is a class of extremely simple and very liberal

licenses for computer software that was originally developed at

the University of California at Berkeley (UCB). It was first used

in 1980 for the Berkeley Source Distribution (BSD), also known

as BSD UNIX, an enhanced version of the original UNIX

operating system that was first written in 1969 by Ken

Thompson at Bell Labs.

The only restrictions placed on users of software released

under a typical BSD license are that if they redistribute such

software in any form, with or without modification, they must

include in the redistribution (1) the original copyright notice, (2)

a list of two simple restrictions and (3) a disclaimer of liability.

These restrictions can be summarized as (1) one should not

claim that they wrote the software if they did not write it and (2)

one should not sue the developer if the software does not

function as expected or as desired. Some BSD licenses

additionally include a clause that restricts the use of the name

of the project.

The permissive nature of the BSD license allows companies to

distribute derived products as proprietary software without

exposing source code and sometimes intellectual property to

competitors. Searching for strings containing "University of

California, Berkeley" in the documentation of products, in the

static data sections of binaries and ROMs, or as part of other

information about a software program, will often show BSD

code has been used. This permissiveness also makes BSD

code suitable for use in open source products, and the license

is compatible with many other open source licenses.

BSD operating systems can run much native software of

several other operating systems on the same architecture,

using a binary compatibility layer. Much simpler and faster than

emulation, this allows, for instance, applications intended for

Linux to be run at effectively full speed. This makes BSDs not

only suitable for server environments, but also for workstation

ones, given the increasing availability of commercial or closed-

source software for Linux only. This also allows administrators

to migrate legacy commercial applications, which may have only

supported commercial Unix variants, to a more modern

operating system, retaining the functionality of such applications

until they can be replaced by a better alternative.

GNU GENERAL PUBLIC LICENSE

The GNU General Public License (GNU GPL or simply GPL) is

a widely used free software license, originally written by Richard

Stallman for the GNU project.

The GPL is an example of a powerful copyleft license that

requires derived works to be available under the same copyleft.

Under this philosophy, the GPL grants the recipients of a

computer program the rights of the free software definition and

uses copyleft to ensure the freedoms are preserved, even when

the work is changed or added to. This is in distinction to

permissive free software licenses, of which the BSD licenses

are the standard examples.

The GPL was designed as a license, rather than a contract. In

some Common Law jurisdictions, the legal distinction between a

license and a contract is an important one: contracts are

enforceable by contract law, whereas licenses are enforced

under copyright law. However, this distinction is not useful in the

many jurisdictions where there are no differences between

contracts and licenses, such as Civil Law systems.

Those who do not agree to the GPL's terms and conditions do

not have permission, under copyright law, to copy or distribute

GPL licensed software or derivative works. However, if they do

not redistribute the general public licensed program, they may

still use the software within their organization however they like,

and products constructed by the use of the program are not

covered by this license

APACHE LICENSE

The Apache License is a free software license authored by the

Apache Software Foundation (ASF). The Apache License

requires preservation of the copyright notice and disclaimer, but

it is not a copyleft license — it allows use of the source code for

the development of proprietary software as well as free and

open source software.


Fiat Lux! 02/2010

All software produced by the ASF or any of its projects or

subjects is licensed according to the terms of the Apache

License. Some non-ASF software is licensed using the Apache

License as well. As of July 2009, over 5000 non-ASF projects

located at SourceForge.net are available under the terms of the

Apache License. In a blog post from May 2008 Google

mentioned that 25% of the 100,000 projects then hosted on

Google Code were using the Apache License.

PHP LICENSE

The PHP License is the software license under which the PHP

programming language is released. The PHP License is a non-

copyleft free software license according to the Free Software

Foundation and an open source license according to the the

Open Source Initiative. This license is GPL-incompatible due to

restrictions on the use of the word PHP.

MIT LICENSE

The MIT License is a free software license originating at the

Massachusetts Institute of Technology (MIT), used by the MIT X

Consortium. It is a permissive license, meaning that it permits

reuse within proprietary software on the condition that the

license is distributed with that software. The license is also

GPL-compatible, meaning that the GPL permits combination

and redistribution with software that uses the MIT License.

According to the Free Software Foundation, the MIT License is

more accurately called the X11 license, since MIT has used

many licenses for software and the license was first drafted for

the X Window System.

Software packages that use the MIT License include Expat,

PuTTY, the Mono development platform class libraries, Ruby on

Rails, Lua (from version 5.0 onwards), and the X Window

System, for which the license was written.

Some software packages dual license their products under the

MIT License, such as the JavaScript library jQuery, which is

licensed under both the MIT and GNU General Public License

licenses.

MOZILLA PUBLIC LICENSE

The Mozilla Public License (MPL) is a free and open source

software license. Version 1.0 was developed by Mitchell Baker

when she worked as a lawyer at Netscape Communications

Corporation and version 1.1 at the Mozilla Foundation. The

MPL is characterized as a hybridization of the modified BSD

license and GNU General Public License.

The MPL is the license for the Mozilla Application Suite, Mozilla

Firefox, Mozilla Thunderbird and other Mozilla software. The

MPL has been adapted by others as a license for their software,

most notably Sun Microsystems, as the Common Development

and Distribution License for OpenSolaris, the open source

version of the Solaris 10 operating system, and by Adobe, as

the license for its Flex product line.

The license is regarded as a weak copyleft. Specifically, source

code copied or changed under the MPL must stay under the

MPL. The MPL was approved both as an Open Source software

license by the Open Source Initiative and as a Free Software

license by the Free Software Foundation.

ECLIPSE PUBLIC LICENSE

The Eclipse Public License (EPL) is an open source software

license used by the Eclipse Foundation for its software. It

replaces the Common Public License (CPL) and removes

certain terms relating to patent litigation.

The Eclipse Public License is designed to be a business-

friendly free software license, and features weaker copyleft

provisions than contemporary licenses such as the GNU

General Public License (GPL). The receiver of EPL-licensed

programs can use, modify, copy and distribute the work and

modified versions, in some cases being obligated to release

their own changes.

The EPL is approved by the Open Source Initiative (OSI) and

the Free Software Foundation (FSF).

BEYOND SOFTWARE

Most of these licenses deal with the freedoms relating to

software. However many of these licenses are not confined to

software. Licenses such as creative commons, for instance, are

used increasingly for intellectual property beyond software.

The best example of this is wikipedia, where the content of each

and every article is subject to the creative commons license. It

is not uncommon for one to find ebooks, blogs etc that are

subject to creative commons licensing.

An extension of this idea can apply to even print media. If you

have not by now noticed it, the bottom right of this page has the

creative commons license symbol. It means that each and

every article and content in this publication is subject to creative

commons licensing.

So do feel free to copy, modify, and redistribute :-)


Fiat Lux! 02/2010

The Man Behind The

Revolution : Richard

Stallman

Revathy Lal

Richard Matthew Stallman (born March

16, 1953), often abbreviated "rms", is an

American software freedom activist, and

computer programmer. In September

1983, he launched the GNU Project to

create a free Unix-like operating system,

and has been the project's lead architect

and organizer. With the launch of the GNU

Project, he initiated the free software movement and, in October

1985, set up the Free Software Foundation.

Stallman pioneered the concept of copyleft and is the main

author of several copyleft licenses including the GNU General

Public License, the most widely used free software license.

[Stallman has also developed a number of pieces of widely-

used software, including the original Emacs, the GNU Compiler

Collection, and the GNU Debugger. He co-founded the League

for Programming Freedom in 1989.

In June 1971, as a first year student at Harvard University,

Stallman was known for his strong performance in Math 55, and

became a programmer at the MIT Artificial Intelligence

Laboratory. There he became a regular in the "hacker"

community. While a graduate student at MIT, Stallman

published a paper on an AI truth maintenance system called

dependency-directed backtracking with Gerald Jay

Sussman.This paper was an early work on the problem of

intelligent backtracking in constraint satisfaction problems. As of

2003, the technique Stallman and Sussman introduced is still

the most general and powerful form of intelligent backtracking.

The technique of constraint recording, wherein partial results of

a search are recorded for later reuse, was also introduced in

this paper. When Brian Reid in 1979 placed "time bombs" in

Scribe to restrict unlicensed access to the software, Stallman

proclaimed it "a crime against humanity." He clarified, years

later, that it is blocking the user's freedom that he believes is a

"crime", not the issue of charging for the software.

In 1980, Stallman and some other hackers at the AI Lab were

refused access to the source code for the software of the first

laser printer, the Xerox 9700. Stallman had modified the

software on an older printer (the XGP, Xerographic Printer), so

it electronically messaged a user when the person's job was

printed, and would message all logged-in users when a printer

was jammed. Not being able to add this feature to the Dover

printer was a major inconvenience, as the printer was on a

different floor from most of the users. This one experience

convinced Stallman of people's need to be free to modify the

software they use. Stallman argues that software users should

have the freedom to "share with their neighbor" and to be able

to study and make changes to the software that they use. He

maintains that attempts by proprietary software vendors to

prohibit these acts are "antisocial" and "unethical". The phrase

"software wants to be free" is often incorrectly attributed to him,

and Stallman argues that this is a misstatement of his

philosophy. He argues that freedom is vital for the sake of users

and society as a moral value, and not merely for pragmatic

reasons such as possibly developing technically superior

software.

In January 1984, Stallman quit his job at MIT to work full-time

on the GNU project, which he had announced in September

1983.

GNU's NOT LINUX!

It is a common misconception among many to think that Linux is

an OS and that GNU is some

company or organization that made

a lot of software in it (gcc, gnome,

etc). GNU is actually an operating

system that has not yet materialized

entirely. Software such as gcc,

emacs, etc credited to Stallman

personally and many others of the

Free Software Foundation and the GNU Project are the pieces

in the puzzle that is to form the OS that is GNU.

GNU is a long running process. Unfortunately, it had a missing

link, its kernel. Linux is the kernel that was used to fill the gap in

the picture. Thus, we today have GNU/Linux. Does this mean

that the GNU project is over? Not at all. Work is still going on

the kernel, named Hurd. Debian has even made a Debian

GNU/Hurd distribution, but being a work in progress it is still

unstable.

Why build another kernel when we have linux? Why not say that

GNU project is complete? The answer to these questions is not

that easy to give. There are philosophical differences amongst

those in the Free Software/Open Source community. One may

not believe it but Richard Stallman and Linus Torvalds have big

differences in opinion when it comes to a number of matters.

We may dig deeper into all these issues when we investigate

the history of Free Software (maybe in another issue).


Fiat Lux! 02/2010

GNU PROJECT AND FREE SOFTWARE

ACTIVISM

In 1985, Stallman published the GNU

Manifesto, which outlined his motivation for

creating a free operating system called GNU,

which would be compatible with Unix.Soon

after, he started a non-profit corporation

called the Free Software Foundation to employ free software

programmers and provide a legal infrastructure for the free

software movementStallman popularized the concept of

copyleft, a legal mechanism to protect the modification and

redistribution rights for free software. It was first implemented in

the GNU Emacs General Public License, and in 1989 the first

program-independent GNU General Public License (GPL) was

released. By then, much of the GNU system had been

completed. Stallman was responsible for contributing many

necessary tools, including a text editor (Emacs), compiler

(GCC), debugger (gdb), and a build automator (gmake). The

notable exception was a kernel. In 1990, members of the GNU

project began a kernel called GNU Hurd.In 1991, Linus

Torvalds, a Finnish student, used the GNU development tools to

produce the Linux kernel. The existing programs from the GNU

project were readily ported to run on the resultant platform;

most sources use the name Linux to refer to the general-

purpose operating system thus formed.

In August 2006 at his meetings with the government of Kerala,

he persuaded officials to discard proprietary software, such as

Microsoft's, at state-run schools. This has resulted in a

landmark decision to switch all school computers in 12,500 high

schools from Windows to a free software operating system.

After personal meetings, Stallman has obtained positive

statements about the free software movement from the then-

President of India, Dr. A.P.J. Abdul Kalam, French 2007

presidential candidate Ségolène Royal, and the president of

Ecuador Rafael Correa.Stallman's staunch advocacy for free

software inspired "Virtual Richard M. Stallman" (vrms), software

that analyzes the packages currently installed on a Debian

GNU/Linux system, and report those that are from the non-free

tree.

Stallman has devoted the bulk of his life’s energies to political

and software activism. Professing to care little for material

wealth, he explains that “I've always lived cheaply … like a

student, basically. And I like that, because it means that money

is not telling me what to do. “


Fiat Lux! 02/2010

Linux vs Windows – For The

Common User

Maxwell Felix

One of the biggest difficulties in migrating from Windows to

Linux is the lack of knowledge about comparable software.

Newbies usually search for Linux analogs of Windows software,

and advanced Linux-users cannot answer their questions since

they often don't know too much about Windows :). Here's a list

of Linux equivalents / replacements / analogs of Windows

software.

Description of

the program,

executed task

Windows Linux

Web browser Internet Explorer, Opera,

Firefox, ...

Firefox, Galeon,

Konqueror, Opera,

Nautilus

Email client Outlook Express,

Thunderbird, ...

Evolution,

Thunderbird,

Kmail, ..

Instant

Messaging

clients

ICQ Lite, ICQ Corp,

MSN,Yahoo, ...

Licq, GnomeICQ,

Pidgin, ..

Work with

compressed

files

WinZip, WinRar, 7-Zip, .. Ark (kdeutils), 7-Zip,

..

Text editor Notepad, WordPad,

TextPad, Vim,

Xemacs, ...

Kedit, Gedit, Vim,

Kate(KDE),

Kedit(KDE), ...

Viewing PDF Adobe Reader,

GhostView, ...

Adobe Reader,

Xpdf, GhostView, ...

Text to speech MS text to speech KDE Voice Pluggin,

Festival,

Emacspeak,

VoiceText, ...

Music / mp3 /

ogg players

Windows Media Player,

Winamp, ...

Mplayer, Xine,

Amarok, ...

Programs for

CD/DVD

burning with

GUI

Nero, Roxio Easy CD

Creator, ...

K3b, Nero, Gnome

Toaster, ...

Graphic Editor Photoshop, Gimp Gimp,

ImageMagick, ..

Office Suite Ms Office, OpenOffice,... OpenOffice,

StarOffice, Koffice,

Tex, LaTeX

Games Civilization: Call To

Power, Quake 1,2,3,

Counterstrike,

Civilization: Call To

Power, Quake

1,2,3, Counterstrike,

WYSIWYG

html editor

Dreamweaver, Ms

Frontpage, Mozilla

Composer, OpenOffice

HTML editor

Mozilla Composer,

Openoffice HTML

editor, Amaya, IBM

WebSphere

Homepage Builder,

JXHTMLEDIT(Java)

Web-server Apache, IIS, Roxen, wn,

cern-httpd, dhttpd,

caudium, aolserver, Boa

Apache, Xitami,

Thttp, Boa,

Caudium, Roxen,

Zeus, Thy

Database

engine

MySQL, IBM DB2, MS

SQL, Oracle, ...

PostgreSQL,

MySQL, IBM DB2,

Oracle, ...

Math system

in Matlab style

Matlab Matlab[FTP],

Octave, ....

CAD/CAM/CAE AutoCAD, Microstation,

ArchiCAD

Varcon, Linuxcad,

Varicad, Cycas, ...

Emulation of

the circuit

Electronic Workbench,

Altera MaxPlus+

Geda, Oregano,

Xcircuit, ...

IDE Microsoft VisualStudio

.net, Eclipse, Boa

Constructor, PythonCard

CodeForge,

Kdevelop+Qt3

Designer, Eclipse,

Emacs/Xemacs, ...

Finally, let me add that most Windows software can run very

well in Linux with a little help from the emulator Wine. So if you

can't stop using Photoshop and switch to Gimp, Wine is the way

to go. If you are hooked on that Windows game, Wine can help

you. However remember, you are not truly free when you rely

on an emulator. :)


http://amarok.kde.org/

http://amarok.kde.org/

http://dogma.freebsd-uk.eu.org/~grrussel/index.html

http://www.gnome.org/projects/nautilus/

Fiat Lux! 02/2010

Installing Linux

Vineeth Kartha

The journey of a thousand miles begins with a single step. So

let us start our journey into the world of FOSS with the

installation of any one distro of Linux (UBUNTU 9.10).

The installation of ubuntu 9.10 is amazingly simple and fast

compared to Windows Vista or even windows 7.

But still we'll go through a brief step by step process for

newbies...

1)Insert the cd and restart the system

You will see the wallpaper for a few seconds. When

the installer appears, you will be able to select your native

language for the entire installation process. Click the "Forward"

button to continue...

Where are you?

The second screen will feature a map of the Earth. Upon the

selection of your current location, the time for the final system

will adjust accordingly. You can also select your current location

from the drop down list situated at the bottom of the window.

Click the "Forward" button after you have selected your desired

location...

Test your keyboard

On the third screen, you will be able to choose a desired

keyboard layout. But the default automatic selection should

work for most of you. Click the "Forward" button when you have

finished with the keyboard configuration...

Hard disk partitioning

You have four options here:

1. If you have another operating system (e.g. Windows XP) and

you want a dual boot system, select the first option: "Install

them side by side, choosing between them at each startup."

This option will ONLY appear if you have another operating

system installed, such as Microsoft Windows. Remember that,

after the installation, the Windows boot loader will be

overwritten by the Ubuntu boot loader!

2. If you want to delete your existing operating system, or the

hard drive is already empty and you want to let the installer

automatically partition the hard drive for you, select the second

option, "Use the entire disk."

This option is recommended for most users who do not have

another operating system installed or who want to erase an

existing one, for example Windows OS.

3. The third choice is "Use the largest continuous free space"

and it will install Ubuntu 9.10 in the unpartitioned space on the

selected hard drive.

4. The fourth choice is "Specify partitions manually" and it is

recommended ONLY for advanced users, to create special

partitions or format the hard drive with other filesystems than

the default one. But it can also be used to create a /home

partition, which is very useful in case of reinstalling the whole

system.

Here's how you do a manual partitioning with

/home:

- Select the "Specify partitions manually (advanced) and click

the "Forward" button;

- Make sure that the selected hard drive is the right one.

/dev/sda is the first physical hard drive. /dev/sdb is the second

hard drive in your machine. So, make sure that you know which

is the one you want to format! Otherwise, you will lose ALL


Fiat Lux! 02/2010

YOUR DATA on that hard drive;

- Let's say that the selected drive is empty (no other operating

system or important data on it), but it has some partitions on it.

Select each one of those partitions and click the "Delete"

button. After a few seconds, it will say "free space". Do this with

the other partitions from the selected hard drive, until they're all

deleted and you have a single "free space" line;

- With the "free space" line selected, click on the "Add" button.

In the new window, type 2000 in the "New partition size in

megabytes" field and select the "swap area" option from the

"Use as:" drop down list. Click the OK button and, in a few

seconds, you'll notice a "swap" line with the specified size;


In the new window, select the "Primary" option, type a value

between 10,000 and 50,000 in the "New partition size in

megabytes" field and select / as the "Mount point". Click the OK

button and in a few seconds, you'll notice an "ext4 /" line with

the specified size;


In the new window, select the "Primary" option, type a value

between 30,000 and 50,000 (or whatever space you have left

on the drive) in the "New partition size in megabytes" field and

select /home as the "Mount point." Click the OK button and, in a

few seconds, you'll notice an "ext4 /home" line with the

specified size.

This is how your partition table should look like. If so, click the

"Forward" button to continue with the installation...

WARNING: Be aware that all the data on the

selected hard drive or partition will be ERASED

and IRRECOVERABLE.

Click the "Forward" button to continue with the installation...

Who are you?

On this screen, you must do exactly what the title says. Fill in

the fields with your real name, the name you want to use to log

in on your Ubuntu OS (also known as the "username," which

will be required to log in to the system), the password and the

name of the computer (automatically generated, but can be

overwritten).

Also at this step, there's an option called "Log in automatically."

If you check the box on this option, you will automatically be

logged in to the Ubuntu desktop. Click the "Forward" button to

continue...

Are you really ready for Ubuntu?

Click the "Install" button to start the installation process...

The Ubuntu 9.10 (Karmic Koala) operating system will be

installed...

After approximately 10 to 18 minutes (depending on your

computer's specs), a pop-up window will appear, notifying you

that the installation is complete, and you'll need to restart the

computer in order to use the newly installed Ubuntu operating

system. Click the "Restart Now" button...

The CD will be ejected; remove it and press the "Enter" key to

reboot. The computer will be restarted and, in a few seconds,

you will see the Ubuntu boot splash and Xsplash...


Fiat Lux! 02/2010

Linux Hacking

Vineeth Kartha

Aparna

What makes Linux so special compared to windows? Its the

ability to modify the whole system and make it function

according to our wish. In this column we aim to introduce to you

some basic commands and details that you should know about

Linux. Linux is an operating system that coordinates the

working of the hardware and software and its free of licensing

and such other hurdles a hacker has to face.

GNU/Linux is not that different from other operating systems on

the surface. You point and click using the mouse and call down

menus to get programs to work. However, these icons and

windows are just the sweet candy coating on top of a much

older system, a system of programs designed to be accessed

by the command line.

If you know the correct commands, then you can start any

program, check your computer’s status, and see what files you

have stored without having to find the listing in your menu. The

command line is an interface that allows you to talk directly to

your computer using words called commands

FILES AND FILE SYSTEMS

In Linux everything is treated as a file, the documents that we

save on the system, the directories in which the folders are

present and even the I/O devices are treated as files. Almost

everything you do on a computer involves one or more files

stored locally or on a network. These files are organized in a

hierarchical structure we call the file system. Linux uses the ext

file systems by default (e.g. ext3 or ext4). In this discussion we

would like to use the terns folder and directory to mean the

same.

Your file system's lowest folder / (read as 'root') contains the

following subfolders:

/binEssential user command binaries (for use by all

users)

/bootStatic files of the boot loader, only used at system

startup

/devDevice files, links to your hardware devices like

/dev/sound, /dev/input/js0 (joystick)

/etc Host-specific system configuration

/homeUser home directories. This is where you save your

personal files

/lib Essential shared libraries and kernel modules

/mntMount point for a temporarily mounted filesystem like

/mnt/cdrom

/opt Add-on application software packages

/usr

/usr is the second major section of the filesystem.

/usr is shareable, read-only data. That means that

/usr should be shareable between various FHS-

compliant hosts and must not be written to. Any

information that is host-specific or varies with time is

stored elsewhere.

/var

/var contains variable data files. This includes spool

directories and files, administrative and logging data,

and transient and temporary files.

/procSystem information stored in memory mirrored as

files.

The only folder a normal user needs to use is /home/you/ this is

where you will be keeping all your documents.

e.g.

/home/gecb/Documents

/home/gecb/Music

/home/gecb/Music/malayalam

File names are case sensitive, "myfile" and "MyFile" are totally

different files.

Who and what is root

Linux has one special user called root (this is the user name).

Root is the "system administrator" and has access to all files

and folders. This special user has the right to do anything.

Important jobs like installation of software, the maintenance of

the system, etc are root's job. Practically speaking a non root

user can do no big harm even when they mess up and what

ever harm was done will be done to them and them alone. You

should never log in as root unless you actually need to do

something that requires it!

Use su command to temporary become root and do the things

you need, again: never log into your system as root!

Though there is only one root, we can get privileges if

authorized. The sudo command is used to execute a command

with root privileges, without actually logging in as root.


Fiat Lux! 02/2010

Root is only for system maintenance, this is not a regular user

and using root for everything is a very bad idea!.

You can execute a command as root with:

su -c 'command done as root'

or sudo 'command'.

In OS' like fedora we specify the password for root when we

install it. But in Ubuntu the root password is set by the computer

itself.

Its better to leave it that way but still you can change the root

password by typing

sudo passwd

it will ask for a new UNIX password but its always good to keep

the root user untouched and use the sudo command instead.

There is a group of users (administrators) that are allowed to

use the sudo command only they can use it. Well get into

details of this in another issue.

Opening a command shell / terminal

To learn Linux, you need to learn the shell command line in a

terminal emulator.

In KDE:K → System → Konsoll to get a command shell)

in Gnome:Applications → accessories→ terminal

Pressing CTRL-ALT-F1 to CTRL-ALT-F6 gives you the console

command shell windows, while CTRL-ALT-F7 gives you the

graphical interface.

xterm is the standard XFree console installed on all boxes, run

it with xterm (press ALT F2 in KDE and Gnome to run

commands).

So what is a shell its like a software helps the user to

communicate with the kernel which is actually the soul of the

computer.

The default shell is bash (Bourne Again SHell- named after its

inventor Stephen Bourne) then there are Korn shell, Csh (c

shell) etc. An indepth discussion on all these is left to be

handled in a later column.

The default shell can be changed by typing chsh and then enter

the required shell (ksh or csh)

Your first Linux commands

Now you should have managed to open a terminal shell and are

ready to try your first Linux commands. Simply ask the

computer to do the tasks you want it to using it's language and

press the enter key (the big one with an arrow :-) ). You can add

a '&' after the command to make it run in the background (your

terminal will be available while the job is done). It can be

practical to do things like moving big divx movies or

compressing a large file as a background process.

Commands are written in a particular way. The command is

typed first with no spaces in the name. Then after a space, you

can sometimes modify the command by adding what are called

options. Options change or limit the way the command is

executed. Options are usually preceded by a dash. A command

may also include the name of a file or directory that you want

the command to work on. The finished command will look

something like this.

$command -option file

To get help about any command type

$man 'command name'

ls – list contents of directory

ls lists the files in the current working folder. This is the first

command to try out.

The command may be used in a number of ways:

$ls

$ls -a (displays all files including hidden ones)

$ls -l (long format, displays file type, permissions, owner, etc)

$ls -F (appends * to names of executable. / for directory)

$ls -R (recursively list all subdirectories)

$ls f.png (list file with name f.png if it is in current directory)

As seen in the last example ls allows us to list specific files.

That is,$ls filename lists the file if present in current directory.

This may seem like a useless feature but when combined with

the native support for regular expressions that linux offers we

can do amazing things. For e.g.,

$ls *.png (lists all files with names ending in '.png')

Linux regular expressions are, in simple terms, patterns which

may be matched by a set of file names. This is a topic too big to

be covered in this article. For the moment lets just understand

that as the previous example shows, a * in a file name for a

command represents any string. That is *.png represents the

set a.png, ab2.png, pq.png, etc of files in the current directory.

You may by now guessed that this makes it impossible to have

* in file names. There are many such characters that are not to

be used in file names.

Do note that all files that accept file names as input accept

regular expressions (nothing special to ls).


Fiat Lux! 02/2010

pwd - print name of current/working directory

pwd prints the fully resolved name of the current (working)

director.

cd - change directory

cd stands for change (working) directory and that's what it does.

The folder below you (unless you are in /, where there is no

lower directory) is called "..".

To go one folder down:

$cd..

To change to home folder type:

$cd ~

Change into a folder somewhere else:

$cd /pub/video

The / in front of pub means that the folder pub is located in the /

(lowest folder).

Note that as '..' represents the parent directory '.' represents the

current directory.

chmod – change permissions of a file

The permissions are:

r-read

w-write

x-executable

d- directory

on executing the command ls -l we can see the file names with

the permissions, and they appear as:

-rw-r--r-- 1 gecb gecb 182 2009-12-24 20:02 graph.c

drwxr-xr-x 6 gecb gecb 4096 2009-12-24 20:01 libgraph-1.0.1

here the first part shows the permissions the first character

shows if its a directory or not. Then the next 3 character shows

permission for the owner then comes the permission for the

group and finally comes for the rest of the users.

e.g.,

rwxrwxrwx : the file can be read written and executed b all

rwx --- --- :file can be accessed only by the owner

To make a file executable by any user:

$chmod a+x myfile

Similarly we can use the other permissions too. The permission

can also be entered as octal numbers. rwx -- x--x can be written

as 111001001 in binary and its equivalent octal is 711. So the

command can be issued as chmod 711 myfile

mkdir - makes directory

Folders are created with the command :

$mkdir foldername

To make a long path, use mkdir -p :

$mkdir -p /use/one/command/to/make/a/long/path/

You can make multiple folders in bash and other shells with

{folder1,folder2} :

$mkdir /usr/local/src/bash/{old,new,dist,bugs}

rmdir – remove directory

The command rmdir deletes folders. Usage is of same form as

mkdir. However note that we can only remove empty

directories.

passwd - changes your login password

To change your password in Linux, type:

$passwd

The root user can change the password of any user by running

passwd with the user name as argument:

$passwd gecb

will change gecb's password. Running passwd without

arguments as root changes the root password.

rm - remove

Files are deleted with the command rm:

$rm /home/you/youfile.txt

To delete folders, use rm together with -f (Do not prompt for

confirmation) and -r(Recursively remove directory trees) and

folders must be empty:

$rm -rf /home/you/foo/

cp- copy

Its used to copy a file from source to destination.

$cp source destination

mv- move

Although called move, this command has the added use of

renaming files. It is used as,

$mv source_file destination_file

$mv oldname newname

cat - concatenate

Used to concatenate (combine) two or more files.

$cat file1 file2 > file3


Fiat Lux! 02/2010

Often it is also used to display the contents of a file.

$cat file

more

Used to diplay a file page by page

$more file

less

Similar to more but allows backward movement in file as well as

forward movement.

cal – calendar

To see calendar for current month,

$cal

Other forms of use,

$cal yyyy

$cal mm

$cal mm yyyy

who

To know who all are logged in. An interesting use of it is,

$who am i

which lists your user's details.

shutdown

Used to shutdown the system it should be executed as the root

or using the sudo command. It has several options like

-r for reboot

-P to switch off

-c to cancel the issued shutdown command

the shutdown command can also be issued with time as an

argument so that it shuts down at the specified time.

$sudo shutdown -P +m

where m is the number of minutes to shutdown. To shutdown

instantly use now instead of +m

ln – link

This is used to create symbolic links. A symbolic link is a "file"

pointing to another file. To make a symbolic link,

$ln /original/file /new/link

This makes /original/file and /new/link the same file - edit one

and the other will change. The file will not be gone until both

/original/file and /new/link are deleted.

You can only do this with files. For folders, you must make a

"soft" link. To make a soft symbolic link,

$ln -s /original/file /new/link

E.g.,

$ ln -s /usr/src/linux2 /usr/src/linux

Note that -s makes an "empty" file pointing to the original

file/folder. So if you delete the folder a symlink (symbolic link)

points to, you will be stuck with a dead symlink (just rm it).


Fiat Lux! 02/2010

Comic Corner

LINUX USER AT BEST BUY

WINDOWS 7


Fiat Lux! 02/2010

10 Years Of Linux

Pranoy P

The Linux technology, development model, and community

have all been game-changing influences on the IT industry, and

all we can really do is stand back and look at it all. Much too

much has happened with Linux in the last 10 years to do

anything like a complete job of listing the important events and

technological advances surrounding this operating system.

1. Linux Professional Institute certification

In 2000, LPI announced the availability of test 1a, the first exam

in its new Linux administrator certification program, a program

that now consists of seven tests across three certification levels.

2. Linux Kernel 2.4

The Linux 2.2 kernel was great — for standalone servers and

brave desktop users. It was only after the Linux 2.4 kernel was

introduced in January 2001 that Linux took dead aim at moving

from Web servers and branch file and print servers to running

the enterprise. Yes, it added some desktop-friendly features,

better device support in general and USB support that really

worked, but its improved support for clustering, multiple

processors and up to 64GBs of memory is what paved its way

to being an enterprise server powerhouse.

3. Samba

Andrew Tridgell's Samba with its

implementation of Microsoft's

Server Message Block (SMB)

protocol is such an important component of mixed networks

everywhere that we really didn't feel right not including it here.

4. Linux on S/390

"One box, one operating system" no longer applied to Linux

when it arrived on the S/390 mainframe in early 2000.

5. SE Linux

Released under the GPL by the US National Security Agency in

early 2001 and merged into the kernel since 2.6.0, Security

Enhanced Linux provides support for a number of access

control policy models, such as mandatory access control and

role-based access control.

6.Linux LiveCDs

A LiveCD lets you boot Linux on a machine

without actually installing anything on the hard

drive—Linux boots from the CD or DVD and

lives in RAM while running. Many distributions have LiveCD

versions, and there are a number of LiveCD distributions

created for specific tasks, such as system diagnosis and

recovery.

7. Linux clusters

Linux users early on started chaining multiple boxes together to

provide more fault tolerance or better performance. Beowulf, for

one, was an important early architecture for multi-machine

parallel computations. There's even a load-balancing cluster

LiveCD, ClusterKnoppix.

8. Linux supercomputing

Of course, tightly coupled, multi-core systems will always

outperform networked boxes. Blue Gene®/L and the now Blue

Gene/P running Linux are setting records in the most compute-

intensive technical and scientific workload environments.

9. Linux on Playstation

Sony has allowed and even

encouraged the installation of Linux

on its game consoles, and for

developers interested in exploring

Cell/B.E. programming, the PS3 is an

accessible option. Linux on the

Playstation makes a fine computer and all, but frankly, in the

greater scheme of things, we're not sure it changes the Linux

landscape all that much.

10. Virtualization

Virtualization allows one or more guest operating systems to run

on top of another operating system that acts as the host. The

2.6.20 kernel was the first to include the Kernel Virtual Machine

(KVM), but Xen, User-Mode Linux, QEMU, VMware, and other

virtualization technologies are important as well.

11. One Laptop Per Child

Announced in 2005, the OLPC project

was created to provide low-cost,

durable, connected computers to

underprivileged children around the

world. As much about the user interface

as the hardware, the Linux-based Sugar operating environment

is designed to encourage exploring and expressing rather than

focusing on traditional productivity tools.

12. Ubuntu

When South African millionaire Mark

Shuttleworth’s company, Canonical,


Fiat Lux! 02/2010

released the Debian-based Ubuntu in 2004, few could have

expected what a massive success it would become. Ubuntu

quickly became the most widely used Linux distribution by far,

especially on the desktop, and has brought Linux to the masses

like no other distribution.

13.Cellphones

Linux on cellphones is fast becoming popular and is being

adopted by major manufacturers line Nokia and HTC. We have

the revolutionary Nokia N900 running Maemo and the HTC

Hero running Google Android. Both are Linux for smartphones

and are highly customizable and developer friendly.

14. The Netbook arrives

Perhaps it wasn't too surprising that Dell was followed by Asus,

which introduced a new kind of laptop: the Linux-powered

netbook. Netbooks quickly became wildly popular, which caught

everyone by a surprise — no one more so than Microsoft, which

was forced to bring XP Home out of retirement to compete with

Linux.

Today, despite Microsoft's claims that Windows has beaten

Linux out of the low-end netbook space, Linux is holding its own

on the global market. Indeed, the entire netbook and desktop

Linux market may be in for a complete revolution thanks to the

arrival of the most recent desktop Linux player: Google.

15.Oracle buys Sun

The decade ends with the sun

setting on one of the most

influential Unix and open source

companies to survive the 90s.

Custodian of Java, VirtualBox,

MySQL and OpenOffice.org, along with major contributions to

Gnome, Mozilla and the Linux kernel itself, the effects of Sun's

acquisition are yet to be realised. But whatever happens to Sun,

these projects are safeguarded, thanks to the open source

licences they use.

16. Google Chrome OS

Google, one of the only companies in the world

that's big enough to go head-to-head with

Microsoft, has thrown its hat into the desktop OS

ring with the announcement of the 2010 arrival of

the Chrome operating system. What I think makes this move

both especially interesting, and more likely to succeed, is that

Google isn't taking on Windows 7 on all desktops. No -- what

Google is doing is claiming that its Internet-based, Linux-

powered Chrome OS is all the 'desktop' people will need on

low-end systems like netbooks.

17. Cloud Computing

Cloud Computing has become the next buzzword for quite

some years, both bygone and the ones to come. From cloud

based storage to providing software as a service(SaaS), Cloud

Computing is really picking up on Desktop based computing.

Linux has a major role to play in Cloud Computing as we

already have a good number of Cloud based operating systems

and certain cloud based services supported in Linux. gOS,

Google Chrome OS and Ubuntu One are a few popular ones.


Fiat Lux! 02/2010

A Quick Look at C

Maxwell Felix

C is a very simple programming language. Something very hard to digest when we consider its power. In fact we call a family of laguages “C-like” due to their shared syntax and history. This includes those like C++, Java, Perl, PHP, etc. A thorough understanding of C is surely going to aid in learning any of these languages. So lets get started.What you need to start?First and foremost, what is needed is a c compiler. The compiler of choice is gcc from GNU. Its in all linux distributions. For the windows user a good choice would be Dev C++ ( don't worry about the name, C works in it ).The First ProgramIn the spirit of an ancient tradition, all first programs in a new language do just one simple thing. When executed, the display the words “Hello World!” on the screen.#include<stdio.h>int main(){

printf(“Hello World!”);return 0;

}Lets now examine what exactly we see in the above program of ours. The first line starting with the hash (#) is meant to include header files into our program.A header file in general holds part of our program that we have separated into a number of files. The above program is a very small one but in real life programs tend to be thousands of lines long and separating it into a number of files allows it to be easier to handle and understand.The header file included in our program is called 'stdio.h'. It holds the programs that we use for standard input/output (hence the name). An obvious question would be, “Who made this header file?” This header file is part of group of a number of other header files that are together called the C Standard Library. This essentially is a set of programs that have already been provided with the compiler for our use. They surely make a programmer's life a lot easier.Following the #include we find the int main() followed by flower brackets ({}) inside which we have some program code. This is called the main function. For the moment understand that all C programs will have the main(){ }. In C, the { and } symbols mark the beginning and end of a block of code. In this case, the block of code making up the main function contains two lines.The printf statement allows us to send output to standard output (display terminal).The return 0 returns an error code of 0 to the shell (which started the execution) that there was no errors.Lets get formalThe variablesA C variable may be thought of as a container that is used to hold a value. C requires us to declares all the variables that we use. A declaration tells C the name and type of the variable. For eg int i; declares a variable with name i and type int (integer).C supports a number of other standard types for variables such as char (for charcters), float (for real numbers), etc. All types of variables are declared int the same way,<type> <name>;e.g.int i;float ff;char o;There are a conditions that C imposes on variable declaration. 1. All variable declarations should be at the begining of a block ( {} ).

2. The names of variables should not be a number or special character (*,&,+,-, etc).3. Variable names are case sensitive. i.e apple is not aPpleNow lets see how all that we've seen so far is implemented in an actual program.#include <stdio.h> int main() { int a, b, c; a = 5; b = 7; c = a + b; printf("%d + %d = %d\n", a, b, c); return 0; }Here we have 3 integer variables a, b and c. Note that, we can declare more than one variable of a type by separating the names with a comma (,).We have stored (assigned) the value 5 to a, 7 to b, and the sum of a and b to c.The printf statement then prints the line "5 + 7 = 12." The %d placeholders in the printf statement act as placeholders for values. There are three %d placeholders, and at the end of the printf line there are the three variable names: a, b and c. C matches up the first %d with a and substitutes 5 there. It matches the second %d with b and substitutes 7. It matches the third %d with c and substitutes 12. Then it prints the completed line to the screen: 5 + 7 = 12. The +, the = and the spacing are a part of the format line and get embedded automatically between the %d operators as specified by the programmer.We use %d if the corresponding variable is integer, %c if character, %s for strings, and so on.User InputLets now accept the numbers from the user and display the sum.#include <stdio.h> int main() { int a, b, c; printf("Enter the first value:"); scanf("%d", &a); printf("Enter the second value:"); scanf("%d", &b); c = a + b; printf("%d + %d = %d\n", a, b, c); return 0; }Note that we have used a new statement called scanf. It looks a lot like printf in syntax but it accepts the input from the user into the specified variables. Also note that the variable names are given after an &.Branching and Looping In C, both if statements and while loops rely on the idea of Boolean expressions. Here is a simple C program demonstrating an if statement: #include <stdio.h> int main() { int b; printf("Enter a value:"); scanf("%d", &b); if (b < 0) printf("The value is negative\n"); return 0; }This program accepts a number from the user and tests it using an if statement to see if it is less than 0. If it is, the program prints a message.Here's slightly more complex example: #include <stdio.h> int main()


Fiat Lux! 02/2010

{ int b; printf("Enter a value:"); scanf("%d", &b); if (b < 0) printf("The value is negative\n"); else if (b == 0) printf("The value is zero\n"); else printf("The value is positive\n"); return 0; } In this example, the else if and else sections evaluate for zero and positive values as well. Here is a more complicated Boolean expression: if ((x==y) && (j>k)) z=1; else q=10; This statement says, "If the value in variable x equals the value in variable y, and if the value in variable j is greater than the value in variable k, then set the variable z to 1, otherwise set the variable q to 10." You will use if statements like this throughout your C programs to make decisions. In general, most of the decisions you make will be simple ones like the first example; but on occasion, things get more complicated. Notice that C uses == to test for equality, while it uses = to assign a value to a variable. The && in C represents a Boolean AND operation. Here are all of the Boolean operators in C: equality == less than < Greater than > Less than or equal <= Greater than or eual >= inequality != and && or || not ! You'll find that while statements are just as easy to use as if statements. For example: while (a < b) { printf("%d\n", a); a = a + 1; } This causes the two lines within the braces to be executed repeatedly until a is greater than or equal to b. This kind of repeated execution is called looping.C also provides a do-while structure: do { printf("%d\n", a); a = a + 1; } while (a < b); The differece between while and do-while is that the latter causes the block of code to be executed even when the condithion of while is false.The for loop in C is simply a shorthand way of expressing a while statement. For example, suppose you have the following code in C: x=1; while (x<10) { blah blah blah x++; /* x++ is the same as saying x=x+1 */ } You can convert this into a for loop as follows: for(x=1; x<10; x++) { blah blah blah

} Boolean expressions evaluate to integers in C, and integers can be used inside of Boolean expressions. The integer value 0 in C is False, while any other integer value is True. The following is legal in C: #include <stdio.h> int main() { int a; printf("Enter a number:"); scanf("%d", &a); if (a) { printf("The value is True\n"); } return 0; } If a is anything other than 0, the printf statement gets executed.ArraysAn array lets you declare and work with a collection of values of the same type. For example, you might want to create a collection of five integers. One way to do it would be to declare five integers directly: int a, b, c, d, e; This is okay, but what if you needed a thousand integers? An easier way is to declare an array of five integers: int a[5]; The five separate integers inside this array are accessed by an index. All arrays start at index zero and go to n-1 in C. Thus, int a[5]; contains five elements. For example: int a[5]; a[0] = 12; a[1] = 9; a[2] = 14; a[3] = 5; a[4] = 1;One of the nice things about array indexing is that you can use a loop to manipulate the index.#include <stdio.h> #define MAX 10 int a[MAX]; int main() { int i; for (i=0; i < MAX; i++) { a[i]=i; printf("%d\n",a[i]); } return 0; }This program has a lot of new stuff. Lets begin with the #define, it is used to define a macro. Here the macro MAX stands for the constant value 10. A macro is not a variable but just a simple way to represent a constant. So MAX=5 is wrong but i=MAX is correct if we have a variable i.Another new thing in this program is the declaration of array outside main(){}. This is perfectly ok. This type of variables are called global variables. We will deal with them later when we discuss functions.Structures Structures in C allow you to group variable into a package. Here's an example: struct rec { int a,b,c; float d,e,f; }; struct rec r; As shown here, whenever you want to declare structures of the type rec, you have to say struct rec. This line is very easy to forget, and you get many compiler errors because you absent-


Fiat Lux! 02/2010

mindedly leave out the struct. You can compress the code into the form: struct rec { int a,b,c; float d,e,f; } r; where the type declaration for rec and the variable r are declared in the same statement. Or you can create a typedef statement for the structure name. For example, if you do not like saying struct rec r every time you want to declare a record, you can say: typedef struct rec rec_type; and then declare records of type rec_type by saying: rec_type r; You access fields of structure using a period(.), for example, r.a=5;.Do note that we can have arrays of structures as we have arrays of other types.FunctionsMost languages allow you to create functions of some sort. Functions let you chop up a long program into named sections so that the sections can be reused throughout the program. Functions accept parameters and return a result. C functions can accept an unlimited number of parameters. In general, C does not care in what order you put your functions in the program, so long as a the function name is known to the compiler before it is called. Function names should not begin with numbers or special characters just like variable names.#include<stdio.h>int fact(int i) { int j,k;

j=1; for (k=2; k<=i; k++) j=j*k; return j; }int main() { int i,b; scanf("%d", &b); i=fact(b); printf("%d\n",a[i]); return 0; }Here fact is a function accepting an integer argument (i) and returning another integer (j). It is now considered good form to use function prototypes for all functions in your program. A prototype declares the function name, its parameters, and its return type to the rest of the program prior to the function's actual declaration.#include <stdio.h>int add (int,int); /* function prototype for add */void main(){ printf("%d\n",add(3));}int add(int i, int j){ return i+j;}Note that functions can have any type of variable as parameter even arrays and structures.PointersTo understand pointers, it helps to compare them to normal variables. A "normal variable" is a location in memory that can hold a value. For example, when you declare a variable i as an integer, four bytes of memory are set aside for it. In your program, you refer to that location in memory by the name i. At the machine

level that location has a memory address. The four bytes at that address are known to you, the programmer, as i, and the four bytes can hold one integer value.

A pointer is different. A pointer is a variable that points to another variable. This means that a pointer holds the memory address of another variable. Put another way, the pointer does not hold a value in the traditional sense; instead, it holds the address of another variable. A pointer "points to" that other variable by holding a copy of its address. Because a pointer holds an address rather than a value, it has two parts. The pointer itself holds the address. That address points to a value. There is the pointer and the value pointed to. This fact can be a little

confusing until you get comfortable with it, but once you get comfortable it becomes extremely powerful. The following example code shows a typical pointer: #include <stdio.h> int main() { int i,j; int *p; /* a pointer to an integer */ p = &i; *p=5; j=i; printf("%d %d %d\n", i, j, *p); return 0; } The first declaration in this program declares two normal integer variables named i and j. The line int *p declares a pointer named p. This line asks the compiler to declare a variable p that is a pointer to an integer. The * indicates that a pointer is being declared rather than a normal variable. You can create a pointer to anything: a float, a structure, a char, and so on. Just use a * to indicate that you want a pointer rather than a normal variable. The line p = &i; will definitely be new to you. In C, & is called the address operator. The expression &i means, "The memory address of the variable i." Thus, the expression p = &i; means, "Assign to p the address of i." Once you execute this statement, p "points to" i. Before you do so, p contains a random, unknown address, and its use will likely cause a segmentation fault or similar program crash.Here is a cool aspect of C: Any number of pointers can point to the same address. For example, you could declare p, q, and r as integer pointers and set all of them to point to i, as shown here: int i; int *p, *q, *r;

p = &i; q = &i; r = p; Note that in this code, r points to the same thing that p points to, which is i. You can assign pointers to one another, and the address is copied from the right-hand side to the left-hand side during the assignment.Something to note in C is that pointers to structures use the operator -> to access members. There is also an interesting type of poiter called pointer to functions. What next?C is simple but its not all that simple to be distlled down to a three page article. However, this article has enough stuff in it to enable you to go the rest of the way on your own. So go ahead, find out about structure pointers, what a function pointer is, and so on.You have been shown the light. The rest is up to you :-)


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