Units of Computers:
1. Input Units:
     The set of input devices is called input units.
Or those units whose work is to give data to the processor is called input unit.

Input Devices:
Keyboard, Mouse, Scanner, Digital Camer, Joy Stick.

2. CPU:
  • CPU stands for Central Processing Unit.
  • TO Control and monitor all activities of the computer.
  • Also called the brain of the computer.
Component of CPU:
There are two main components of CPU;
(i)
Processor
(ii)
Storage
i. Processor:
    This part of the CPU performs all the activities of the computer system.
Parts of processor:
Again divided into 2 types;
(a)
 ALU Arithmetic Logic Unit
(b)
 CU Control Unit
a. ALU:
    This unit performs all the arithmetic and logic activities.
b. CU:
    As the name indicates that this unit control all the activities of the computer.

ii. Storage:
    The part of the CPU is used to store all types of data.
Parts of Storage:
a. Primary Storage Unit:
    The nature of primary storage is volatile means when the computer is shut down all electric power failures the data stored in this part is cleared/erase.
b. Secondary Storage Unit:
    As its name indicates that this unit controls all the activities of the computer system. The nature of this storage unit is non-volatile means data is permanently stored in this part of storage.

3. Output Unit:
     The set of output devices is called the output unit OR the part of a computer which is associated to show output whether in the form. A hard copy or soft copy is called an output unit.

Devices/ Output Units:
(1)
Monitor
(2)
Speaker
(3)
Potter
(4)
Printer
Storage Devices:
(1)
Hard Disk  
(2)
Floppy Disk
(3)
Compact Disk
(4)
USB
Categories of Hardware:
Peripheral Devices:
    Those devices which are directly connected to processors e.g All output devices All input devices.
Non-Peripheral Devices:
    Those devices are non-directly connected to processors. e.g All storage devices (USB, CD, ROM)

Software:
    Those devices are untouchable.

Categories of Software:
1. System Software:
    The type of software that is essential for S.S again recognized in 3 classes.

i. Translator:
    The type of system software that is essential to convert human-like language into binary language.
Human Language---Binary Langauge
Type of translator:
a. Assembler:
    That type of translator is specific to translating assembly language to binary language and vice versa.
b. Compiler:
    That type of translator that translates any language into machine language as a whole is called an interpreter.
c. Interpreter:
    The type of translator which translates any language binary language and vice versa line by line is called an interpreter.

ii. Device Driver:
    The type of system software that is specific to drive any hardware.
e.g Driver of Printer.
Driver of Scanner

iii. Operating System:
    The type of system software that is specific to operating the whole system else called an operating system.
e.g. Windows, Android, Apple, etc.

2. Application:
    The type of software that is designed for the user is called application.
e.g. Ms.word, Ms.Exel, Ms.Power Point etc.