Computer Knowledge: Computer Architecture for Competitive Exam Preparation

Computer Architecture

In computer science, computer architecture is a set of disciplines that describes the part of computer system and their relations. Computer architecture deals with the functional behaviour of a computer system as viewed by a programmer. It can also be described as the logical structure of the system unit that housed electronic components. The computer architecture forms the back bone for building successful computer systems.

Components of a Computer:Input/Output (I/O) Unit

• ( i ) Central Processing Unit (CPU)
• ( ii ) Memory Unit

( i ) Input Unit: The computer accepts coded information through input unit by the user. It is a device that is used to give required information to the computer.Ex:- keyboard, mouse, etc.,

( i ) Output Unit: The output unit sends the processed results to the user. It is mainly used to display the desired result to the user as per input instruction. Ex:- video monitor, printer and plotter, etc.,

Central Processing Unit (CPU) :

The central processing unit consists of set of registers, arithmetic and control circuits, which together interpret and execute instructions in assembly language.

The primary functions of the CPU are:

• The CPU transfers instructions and input data from main memory to registers i.e., internal memory.
• The CPU executes the instructions in the stored sequence.
• When necessary, CPU transfers output data from registers to main memory.

The CPU consists of three main sub-systems; 

• ( i ) Arithmetic Logic Unit (ALU). 
• ( ii ) Control Unit (CU).
• ( iii ) Registers.

( i ) Arithmetic Logic Unit(ALU):

It is used to perform all arithmetic calculations and logical calculation. Logical unit performs comparison of numbers, letters and special characters. ALU uses registers to hold the data that is being processed.

( ii ) Control Unit (CU):

Control unit coordinates with the input and output devices of a computer. It directs the computer to carry out stored program instructions by communicating with the ALU and the registers. It organises the processing of data and instructions. To maintain the proper sequence of processing data, the control unit uses clock inputs. The basic function of control unit is to fetch the instruction stored in the main memory, identify the operations and the devices involved in it and accordingly generate control signals.

( iii ) Registers:  

Registers are special purpose and high speed temporary memory units. Registers are not referenced by their address, but are directly accessed and manipulated by the CPU during execution. Essentially, they hold the information that the CPU is currently working on. Registers store data, instructions, address and intermediate results of processing. The number and sizes of registers vary from processor to processor.

Memory Unit:

Memory is that part of the computer, which holds data and instructions. Memory is an integral component of the CPU. 

The memory unit consists of ( i ) Primary memory and ( ii ) Secondary memory.

( i ) Primary Memory:

Primary Memory or main memory of the computer is used to store the data and instructions during execution of the instructions. The primary memory is of two types; Random Access Memory (RAM) and Read only Memory (ROM).

Random Access Memory(RAM) : It directly provides the required information to the processor. RAM is a volatile memory. It provides temporary storage for data and instructions. RAM is classified into two categories

• Static Random Access Memory (SRAM)
• Dynamic Random Access Memory (DRAM)

Read Only Memory (ROM): It is used for storing standard processing programs that permanently reside in the computer. Generally, designers program ROM chips at the time of manufacturing circuits. ROM is a non-volatile memory. It can only be read not written. ROM is classified into three categories.

• Programmable ROM (PROM)
• Erasable Programmable ROM (EPROM)
• Electrically Erasable Programmable ROM (EEPROM)

( ii ) Secondary Memory:

Secondary memory, also known as secondary storage or auxiliary memory, is used for storing data and instructions permanently Ex;- hard disks, CD's, DVD's etc.,