Computer System

The computer is designed to manipulate all types of data in the form of information. It is an electronic device in which data and control flow through bus in the form of digital pulse. It has mainly two parts: CPU and Pheripherals.



(a) CPU (microprocessor):

The Central Processing Unit of computer is called CPU. It is a brain of computer and its main components are: main memory, ALU and control unit. In 1972, Intel introduced 200KHZ 8008 chip, the first commercial 8-bit microprocessor. It accesses 16 KB of memory. The speed of this microprocessor was 60,000 instructions per second. The invention of microprocessor is stepping stone in popularity of PC.

There are many manufacturers are engaged in the production of microprocessors.


(b) Computer peripherals:

All the part of computer except CPU is termed as computer peripherals. Some peripherals are in- built peripherals (Sound Card, Video Card, Internet Card), and some are connected very close to CPU (Hard Disk, CD-ROM), and some placed out of CPU (Key board, Monitors, Printers).


Control Organization:

There are two popular control organizations:

(i) Hardwired Control: In hardwired control system gates, flip-flops, decoders and other logic circuits are built control logic to produce a fast mode of operation. The wiring between several logical circuits is responsible for performance of control unit.

(ii) Microprogrammed Control: This type of organization has no dedicated circuitry like hardwired control organization, so it is no fast. The control instructions are stored in control memory. The control memory is programmed to initiate the required sequences of micro-operation. The change or modification can be done through instruction codes.


The Instruction sets:

The set of instruction coded in binary to control computer hardware is called instruction set. These instruction set is loaded to memory to run computer. Every computer has its own Instructions set. Instructions are given with the help of instruction codes.

It has two parts:

(i)  Operation Part: Specifies the operation to be performed.

(ii)  Operand: Specifies a memory address that tells the control where to find out operand in the memory.



(a) LDA: It loads the accumulator (register)

Example: LDA 4A.


(b) ADD: Add the contents of memory location to the content of accumulator.

Example: ADD FH


(c) SUB: Subtract from content of accumulator. Example: SUB 5H


(d) STA: used to store content of accumulator into memory address.


(e) JMP: It is used to get next instruction from memory address.


(f) OUT: The content of accumulator is transferred to output port.


(g) HLT: It tells the computer to stop processing of data. HLT marks the end of the program.

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