Introduction To Computer

 COMPUTER:- COMPUTER IS A PROGRAMMABLE ELECTRONIC DEVICE WHICH IS SPECIALLY DESIGNED FOR MAKING CALCULATION AND STORES THEM.

Computer Hardware: Physical component and circuitry of computer is called as computer hardware. A physical device may be electronic, magnetic, mechanical, or optical device.

Program: A set of meaningful instruction to perform a specific task is called as program

Computer software: A set of programs written for a particular computer is called as software.

Firmware: “Software on a Chip”; programs stored in ROM, PROM, EEPROM is called as firmware.

CPU: The Central Processing Unit (CPU) fetches instructions from the memory and performs specific tasks. It stores results in the main memory or sends result to the output device according to instruction given in the program. The CPU controls and communicates with memory and input/output devices. Under the control of CPU programs and data are stored in the memory and displayed on CRT. The schematic diagram of a CPU is shown in figure 1.2

The major sections of CPU are:

(i) ALU (arithmetic and logic unit) the function of ALU is to perform arithmetic operations such as addition, subtraction; and logical operations such as AND, OR, EX-OR.

(ii) Timing and control unit: this unit controls the entire operations of computer. It acts as a brain. It also controls all other devices connected to CPU. It generates timing signals necessary for input and output devices.

(iii) Accumulator and general purpose registers: the accumulator is register which contains one of the operands and stores results of most arithmetic and logical operations General purpose registers are used for temporary storage of data and intermediate results while computer is making execution of a program. Special purpose registers are used by microprocessor itself. They are not accessible to programmers.

Memory: The memory is a storage device. It stores programs, data, results etc.

Input device: The computer receives data and instruction through input devices. An input device converts instruction, input data and signals into proper binary form suitable for a digital computer. The keyboard and mouse are simple input devices.

Output device: The computer sends results to output devices. An output device may store, print, display or send electric signals to control/actuate certain equipment.

A digital computer understands information’s composed of only zeros and ones. It uses binary numbers for its operations. There are only two digits 0 and 1 in the binary number system. A binary digit is known as bit

A group of 8-bit is called as byte.

1024 bytes = 1 kilo byte (MB)

1024kilo byte = 1 mega byte (MB)

1024 Mega bytes = 1 Giga byte (GB)

1024 Giga bytes = 1 Tera byte (TB)

The number of bits that a digital computer can process in parallel at a time is called its word length.

The instructions are coded and stored in memory in the form of zeros and ones. A computer can do what the programmer asks to do. To perform a particular task the programmer prepares a set of instructions known as program. A program written in the form of zeros and ones is called as machine language program. The writing of a program in the machine language is very difficult, tiresome, boring and error prone. Hence, to facilitate programmers easily understandable languages have been developed. The simplest symbolic language used for microprocessor is known as assembly language. The program written for one microprocessor can not be used for any other microprocessor. It is not universal. Languages resembling English and mathematics have been developed for computers. These are known as high level language. Examples of high level language are: BASIC, COBOL, PASCAL. These language are portable. The program written in a high level language can run on any computer. Large, mini and PC’s are programmed in high level language. Microcomputers used for real time application are programmed in assembly language. Microcomputers designed fro dedicated application usually have fixed program in machine language. An assembly language or high level language is used for the convenience of the programmer but the computer works in machine language. Therefore, translators are used for the conversion of an assembly language or high level language program into machine language program for the operation of the computer. A program which converts an assembly language program into machine language program is called as Assembler. A program which converts translates the high level language program into machine language program is called as compiler. An compiler or assembler is just a program not electronic devices.