1 computer fundamentals. 2 introduction to computers the word computer comes from the word...
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COMPUTER FUNDAMENTALS
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Introduction to Computers
The word “computer” comes from the word “compute", which means, “to calculate”.
Thereby, a computer is a electronics device that can perform arithmetic operations at high speed.
A computer is also called a “data processor” because it can store ,process & retrieve data whenever required.
Introduction to Computers
Software - Word, PowerPoint, Excel, etc. Fun stuff - Games, Photos, etc. Operating Systems – Microsoft, Unix
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Data Processing
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Characteristics of Computer
Automatic
Characteristics
Speed Accuracy No IQ Diligence
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Basic operation of Comp. System
INPUTTING STORING
PROCESSING
OUTPUTTING CONTROLLING
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Basic organization of a computer system
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Input Unit
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Output Unit
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Storage Unit
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Types of Storage
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Central Processing Unit
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Memory Units
Memory is divided into storage locations called memory cells.Associated with each memory location are: 1. Address - position of a cell in memory
2. Contents - info stored
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Memory Units
Everything is manipulated as 0s and 1s stored using two-state devices:
switches, transistors, vacuum tubes.
On/Off states easily compare to the binary numbering system, Base 2.
On = 1, Off = 0 Binary Digit = Bit
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Memory Units
Bits are grouped into bytes ( 8 bits = 1 byte)
Each Memory Cell is 1 byte
Bytes are grouped into words (length is dependent on the machine)
The computer handles data in multiples of bit chunks (bytes)
Data stored in 1 byte
Memory Units
MAIN MEMORY UNIT:
Also called as Primary Memory unit. 2 most important are: RAM ROM They work in different ways and perform
distinct functions.
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RAM (Random Access Memory)
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ROM (Read Only Memory)
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Types of ROM
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Types of ROM
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Cache Memory
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Classification of Computers
Computers Generations
“Generation" in computer talk is a step in technology. It provides a framework for the growth of computer industry.
Till today there are five computer generations:
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Electronics Devices
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Input Devices Also known as Peripheral devices. Used to enter data from the outside world into
primary storage.
For e.g.: Keyboard Mouse Electronic Pen Joystick Scanner ,etc
Keyboard
Mouse
Mouse is a point-and-draw device. Move in all directions.
Electronic Pen Point-and-draw device Used to directly pt with it on the screen to
select icons or to draw graphics on screen. Can write with it on a special pad for direct I/P
of written information to a system.
Joystick
Pointing Device. Moved forward,backward,left & right. Button on the top is provided for selection.
USES:
Commonly used for video games,for controlling industrial robots.
Scanner
,etc.
OCR (Optical Character reader)
l Used to recognize alphanumeric characters.l Reflected light converts into binary no.l Dark area absorb the light whereas light is
reflected by lighted areas.l Reflected light falls on Photocells which
provide binary data corresponding to dark and light areas.
l A B C D E………………………….z
0 1 2…………………………………………...9
‘ - { } % ? etc.
Monitor Printer Speaker Screen image projector ,etc
Monitors are the most popular o/p device used for producing soft-copy of the o/p.
Types of Monitor: CRT Monitor LCD Screens
CRT Monitors
This acronym stands for “Cathode Ray Tube” Very widespread Cheap Good performance
CRT Monitors
The Shadow Mask
Working method of CRT monitor
The back of the tube has a negatively charged cathode, so called electron gun. The electron gun shoots electrons down the tube and onto a positively charged screen. The screen is coated with a pattern of red, green and blue phosphor dots that will glow when struck by the electron stream. The three dots together make up a pixel.
LCD Screens
LCD means Liquid Crystal display
Good quality
How LCD works?
There is a thin liquid cristal layer between a horizontal and a vertical filter. Thanks to an appropriate voltage liquid cristals get arranged and light can pass the filters. This light will appear on the screen.
In color LCDs each individual pixel is divided into three cells, or subpixels, which are colored red, green, and blue. Each subpixel can be controlled independently to yield thousands or millions of possible colors for each pixel.
Printers A computer printer is a device that
produces a hard copy of documents stored, usually on physical print media such as paper.
Main types of PrintersDot matrix
Inkjet
Laser
Drum ,etc.
Dot Matrix Printer
Inkjet Printers
Inkjet Printers
Inkjet Printers
Laser Printers
Laser Printers
Drum Printers They are Line printer coz it print one line at
a time. Have a solid cylindrical drum with
characters embossed on its surface in the form of a circular bands.
Set of hammer mounted in front of the drum in such a manner that an inked ribbon & paper can b placed b/w the hammer & drum.
Drum Printers
It can only print a pre-defined set of characters in a pre-defined style that is embossed on the drum.
The drum would have to complete one full revolution to print each line.
Drum printers are impact printers,hence they can b used to produce multiple copies by using carbon paper.
Drum Printers
Screen Image Projector
Magnetic Tape
Magnetic Tape
Advantages of Magnetic Tape
Limitation of Magnetic Tape
Magnetic Disk
Magnetic Disk
Magnetic Disk
Magnetic Disk
Magnetic Disk Access Time
Magnetic Disk
Floppy Disk
Floppy Disk• Data is recorded on
disk in concentric circular bands called tracks
• Each track is divided into pie-shaped wedges called sectors.Two or more sectors combine to form a cluster.
Floppy Disk Most computers
maintain on the disk a table with the sector and track locations of data. This table, the file allocation table (FAT), enables the computer to locate data easily.
Hard Disk
Zip/Bernoulli Disk
Disk Pack
Winchester Disk
Optical Disks
Optical Disks Storage organization
Types of Optical Disks
CD-R (WORM)
CD-RW
DVD
Optical Disks CD-ROMs: Compact Disc Read-Only
Memory can store up to 6 Mega Bytes
CD-R: Compact Recordable holds the same storage, it is recordable once.
CD-RW: Compact Disc Re-Writeable are read and writable, but does not have the same capacity, because it uses some magnetic technology.
DVDs: Digital Versatile Disc can hold up to 17 Giga Bytes. Used by the contents industries.
OPERATING SYSTEM
A program that acts as an intermediary between a user of a computer and the computer hardware.
Operating system goals: Execute user programs and make solving
user problems easier. Make the computer system convenient to
use. Use the computer hardware in an efficient
manner.
OPERATING SYSTEM
OS is a resource allocator Manages all resources Decides between conflicting requests for
efficient and fair resource use OS is a control program
Controls execution of programs to prevent errors and improper use of the computer
OPERATING SYSTEM
Logical Architecture of a Computer System
This operating system layers hides the details of the hardware from the programmer
Provides the programmer with convenient interface.
Parameters for measuring system performance
Functions of OS
Process Management
Memory Management
File Management
Security
Command Interpretation
Process Management
A process (also called job) is a program in execution.
Process Management manages the processes submitted to a system in a manner to minimize idle time of processors (CPUs,I/O processors,etc.)
Process Management mechanism in early computers
Multiprogramming
Uniprogramming
Multiprogramming System
Process state in multiprogramming
Multitasking
Interleaved execution of multiple jobs (often referred to as task of same user)in a single-user system.
Computer system used for multitasking is uniprocessor systems(having only one CPU)
Multiprocessing
Multiprocessing System
Time-Sharing
Simultaneously interactive use of a computer system.
Short period during which a user process gets to use CPU is known as TIME SLICE,TIME SLOT or QUANTUM.
CPU is taken away from a running process when the allotted time slice expires.
Process State Diagram of Time-Sharing System
Advantages of Time-Sharing
l Reduces CPU idle time.l Provides advantages of quick response time.
Memory Management
l Keeps track of parts of memory in use and parts not in use.
l Allocates memory to processes as needed and deallocates when no longer needed.
Uniprogramming Memory Model
l Used in systems that process one job only at a time.
Multiprogramming Memory Model
Multiprogramming with fixed no. of memory partition
Multiprogramming with variable no. of memory partition
Multiprogramming with variable no. of memory partition
Virtual Memory
Virtual Memory Realization
File Management
File access Method
File Operation
File Extensions
l .c c source program file.l .txt general text file.l .doc microsoft world document file.l .xls microsoft excel spreedsheet file.
Security
l Deals with destruction and unauthorized access.
Types of Security:l External Security : Deals with fire,floods etc.l Internal Security : Deals with user
authentication, access control, cryptography mechanism.
Security
Command Interpretation
Command Interpretation