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 capacityM
  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. Mainframe Computers work at a high speed, and have a high storage capacity
  3. Mini Computers
  4. Mini Computers are medium and powerful Computers.
  5. Micro Computers
  6. Micro Computer are the commonly used as general purpose Computer
  7. Super Computers

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
1. Keyboard
2. Mouse
3. Joystic

Output devices
1. Printer
2. Monitor
3. Dot Matrix Printer
4. Laser printers
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 :
  2. 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
  3. Second – Generation Language:
  4. 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
  5. Third – Generation Language :
  6. 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

  7. Fourth – Generation Language (4GL‟s) :
  8. is a programming language or programming environment designed with a specific purpose in mind, such as the development of commercial business software. In the history of computer science, the 4GL followed the 3GL in an upward trend toward higher abstraction and statement power. The 4GL was followed by efforts to define and use a 5GL.

Development of “C” (Introduction and history)

“C” is a programming language developed at AT & T Bell Laboratories of USA in 1972. It was developed Dennis Ritche in late 1970‟s. it began to replace the more familiar languages of that time like PL/1, ALGOL etc.
  1. “C” became popular because of its reliability, simple and easy to use
  2. It was friendly capable and reliable
  3. ALGOL 60 was developed and did not become popular because it was too general and too abstract.
  4. They developed “CPU” (Combined Programming Language)
  5. Next as it could not come up to make ALGOL 60 better one they moved to “BCPL” (Basic Combines Programming Language. Developed by martin Richard Cambridge university)
  6. At the same time a language called “B” written by ken Thompson at AT & T‟S. Bell laboaratories as a further simplification of BCPL.
  7. “C” s compactness and coherence is mainly due to it‟s one man language. ExLISP, AASCA
Year Lang Developed by Remarks
1960 ALGOL International Committe too general, too abstract
1963 CPL camebridge university Hard to Learn & implementation
1967 BCPL Camebridge university could deal only special problem
1970 B AT&T could deal only special problem
1972 C AT & T Lost Generality of BCPL, B restored
Note : C is a middle level language because it was due to have both a relatively good programming efficiency and relativity good machine effecience.