Computer Science Tutorial

Basics of Computer

Term Computer has become very generic. Any electronics device having any kind of input unit if it does some kind of processing on input value and shows us output can be termed as Computer. For example, even a Calculator can be termed as a small computer.

Computer simply means which computes, that is it does some processing on input values. Even a Mobile/phone is also a small computer. Then why it is called Mobile? Beause its mobile(means which can move). So all phones are kind of mobile computer means they are movable,they can be taken from one place to another easily. Palmtop, Laptop all are kind of computer.

Definition : A Computer is an very fast programmabe electronics device which takes data from users through input devices like keyboard, mouse etc. does arithmatic logical processing on the available data within the CPU and gives us output through a ouput device like monitor.

There are two very important terms related with Computer those are Hardware and Software. If we say Car is the Hardware then Driver is software. Like a Car can not run on its own similarly a computer hardware can not be used without a siftware. Software must be installed within the bare hardware of computer to make it run.

Diffrent Parts of Computer

CPU : Central Processing Unit is the core of Computer. It is the most complex electronics circuitry within a computer which permforms all kind of complex operations. CPU actually doesn't perform all the work itself. It generates signal and distribute the work between different computer resources. Hence it is called brain of the computer. CPU is the fastest element within a computer. It consists of three main parts. ALU, CU, Register. Whenever we talk about CPU its actually processor. However we use both terms interchangibly.

Central Processing Unit(CPU)

Central Processing Unit(CPU)



ALU : Arithmatic Logical unit, its the part of CPU which actually performs all kinds of opeartions. Basically all the operations within a computer is Arithmatical and Logical so its also called Arithmatic Logic unit.



Control Unit : Its the part of computer which gives signal to all other parts of computer and based on the signal only all other parts work. Basically it tells the memory, ALU and input and output devices how to respond to the instructions that is being executed by processor.



Register : It is a very high speed memory which lies inside the cpu chip. Its size is very small like 16KB or 32KB like this. It lies at the top of the memory hierarchy. Its most expensive of all memory and has most complex circuit among all memory circuitry.



Primary Memory : It is one of the important part of computer which holds all currently processing data and instructions within itself. It is volatile in nature, it means once the power goes off, all data and instruction are erased. It lies outside the CPU chip. It is also known as RAM(Random Access Memory).

There are two kinds of RAM
  1. Static RAM (SRAM) - This is used in making cache memory. It is faster but occupies more spcae. It is costlier than DRAM.
  2. Dynamic RAM (DRAM) - This is used in computer RAM. It is slower than SRAM.
Random Access Memory(RAM)

Random Access Memory(RAM)



Secondary Memory: Its a kind of storage for computer. It holds all files and programs permanently. Its non volatile in nature that means it retain its value even after successive power off. Since it's permanent in nature. Computer Operating system is stored here. Ex. Hard Disk, CD, DVD, ROM, Pendrive, Memory Card etc.

Hard Disk

Hard Disk



Input/Output unit : Parts of computer which takes values from user is input unit and part of computer which gives us information after processing is called output unit. Input unit: Keyboard, Mouse, Scanner, Touchscreen, Microphone etc. Output unit: Monitor, Printer, Speaker, Touchscreen etc.



Read only Memory : It is one kind of memory chip which is non volatile in nature. As the name itself suggests it is a memory which can be read only, that is we can not write any thing. It holds one important program/instructions called bootstrap program which is used during booting of computer. This bootstrap program also called BIOS(Basic Input Output System). It's a program written in low level language which performs some basic check like POST (Power on self test) and loads the operating system into memory. Types of ROM

  1. PROM : Programmable ROM
  2. EPROM : Erasable Programmable ROM
  3. EEPROM : Electrically Erasable Programmable ROM
Read only Memory(ROM)

Read only Memory(ROM)

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