Basic Units of Computers:-
According to the 
definition of computer we learn that computer works in an order to complete tasks. It takes 
Input, 
Process Data, Shows 
Output as results and 
Store data (
Temporarily and 
Permanently). 
So We can say that a computer has five basic units in it.
- Input Unit
- Memory Unit (Temporary Storage)
- Processing Unit
- Output Unit
- Storage unit (Permanent Storage)
Input Unit:-
This unit is used to give instructions to Computer. 
It consist of some Keyboard and pointing devices. All the data and 
Instruction are given to computer through this unit. The devices used to
 give data and instructions to computer are called 
input devices. 
Memory Unit:-
This unit works as an interpreter between input, 
processing and output unit. Data and instructions are stored in Memory 
unit before and after processing. It is a temporary memory because it 
only store data when computer is power on. All data is lost when power 
fails or computer is shutdown. RAM (Random Access Memory) is basic part 
of Memory Unit. Its size is measured in MB (Megabytes) or GB (Gigabytes)
Processing Unit:-
The processing unit of a computer consist of a 
processor. A processor is called the brain of computer. It does all the 
works and tasks for computer. It takes data from input unit and process 
it according to the given instructions. Its speed is measured in MHz 
(Mega Hertz).
Output Unit:-
The output unit of computer shows the user what is going inside the computer. It also shows the final results. With the help of this unit computer asks any thing required from the user. Errors are also displayed through this unit. Devices attached to this unit are called output devices. Printer, Monitor, Speakers are examples of the output devices.
Storage Unit:-
 
The storage unit consist of Secondary Storage Devices. It stores the data permanently. Secondary storage device store data magnetically, Electrically or e Optically. Magnetic Tape, Floppy Disk, Zip Disk, Hard disk drive, USB Mass Storage, CD, DVD and Blue Ray Disks are examples of storage devices