UNIT-1
Introduction to computers: A computer is an electronic
device capable of manipulating numbers and symbols under the control of a set
of instructions known as computer program.
They are
different stages of computers (generation)
1.
First
Generation Computers
1. Vacuum
tubes were used which produce more heat
2. Speed of
computing was measured in milliseconds
3. Limited
storage capacity
4. punched
cards were used for I/O operation
2. Second
– Generation Computers
1. Transistors
and diodes were used.
2. Speed of
computing was measured in microseconds
3. Consider
about reduction of heat
4. Remarkable
improvement in reliability
5. Storage
capacity was increased
6. Magnetic
tapes were used instead of punching cards.
3. Third
Generation Computers
1. Integrated
Circuits were used.
2. Speed is
measured in nanoseconds
3. Occupied
less space.
4. devices
like visual display unit for I/O devices
4. Fourth – Generation Computers
1. Use of
micro processor chip
2. Speed was
measured in nano and picoseconds
3. Occupied
less space
4. Commonly
available as personal computers
5. Mini
& micro Computers are developed from micro-processor
5. Fifth – Generation Computers:
1. Use of
super large-scale integration (SLSI) chip in computer (super computers)
2. Capable
of performing millions of instructions per seconds (MIPS)
3. Processing
speed is high.
4. Use of
RICS (reduced instructions set computing) for processing
5. Super
computers are expensive.
Types of Computers
1. Mainframe
Computers
2. Mini
Computers
3. Micro
Computers
4. Super
Computers
Mainframe Computers work at a
high speed, and have a high storage capacity
Mini Computers are medium and
powerful Computers.
Micro Computer are the commonly
used as general purpose Computer
Data Storage in a Computer
1. 4bits = 1
Nibble
2. 8bits = 1
byte
3. 1024
bytes = 1k or 1kb (kilobyte)
4. 1024KB =
1MB (mega byte)
5. 1024MB =
1GB (Gega byte)
6. 1024GB =
1TBC Terabytes
Organization of Computer:
1. Arithmetic
and Logical unit
2. Memory
unit
3. Control
unit
4. Input
unit
5. Output
unit
The Input
and Output units are used to receive and display Inputs & Solutions
Common
i/p & o/p devices : Keyboard, mouse, monitor, printer
The CPU
(Central Processing Unit) Consists of.
1. ALU
(Arithmetic Logic Unit)
2.
CU (Control Unit)
3. MU
(Memory Unit)
1.
The Control Unit Controls all the
activities of the Computer. It sends commands and control signals and finds the
sequence of instruction to be executed.
2.
Memory Unit is the place where all
input data and results are stored. Computer memory is also available in the
form of Random Access Memory (RAM)
3.
ALU Consists of CKTs for
arithmetic operations(+,-,*,/) and logical operations
(<,>,>=,<=,==,!=)
Connected
components of CPU are called peripherals
Input devices Output
devices
1.
|
Keyboard
|
1.
|
Printer
|
2.
|
Mouse
|
2.
|
Monitor
|
3.
|
Joystic
|
3.
|
Dot Matrix Printer
|
4.
Laser printers
|
|
5.LCD
|
|
Storage Devices :
1.
|
Floppy
disk
|
2.
|
Hard
disk
|
3.
|
Compact disk
|
Computer Main Memory :
Primary memory RAM
(Random Access memory)
Secondary memory ROM (Read
only memory)
Hard disk
RAM : It is a temporary storage medium in a computer. The data to be
processed by the computer are transferred from a storage devices or a keyboard
to RAM results from a executed program are also stored in RAM. The data stored
will be erased when the computer is off.
ROM (Read only Memory) : This is a non-volatile or data storage medium
which stores start up programs (operating systems). This essentially stores the
BIOS (Basic Input Operating System)
Note : Basically Computer System components communicate it binaries as
(0‟s & 1‟s, 0 refers OFF state,1 refer ON state)
Languages of different Generation
Computer.
1.
First – Generation Language : All
the instructions are in the binary form and are referred to as machine level or
low level language (LLL). It is very difficult to read the instructions written
in binary
Eg :
00110101011101110001, 101100001010101
2.
Second – Generation Language: all
the instruction are in the forms of mnemonics. The symbolic instruction
language called as Assembly Language. All the symbolic instructions are
converted into binaries with the help of translator called Assembles. ASCII
(American Standard Code For Information Interchange) is commonly used for
translation of source Program into object program
Source Program Eg : ADD A, B, R,
More R,S
Assembler Translated
by Assemble
Object
Program
|
0101
|
10101010
|
0100
|
00001101
|
3.
Third – Generation Language :
These are written in English with symbols and digits. Then are known as High
level language (HLL). common high level languages are c,c++, COBOL, BASIC,
FORTRAN, PASCAL, etc.
For execution the program is translation into
binary form by compiler or interpreter. Source program
Compiler
Object
Prog.
Linker
Executable
Program
Run the
program