Theory:

Classification of Computers:
Based on the design, shape, speed, efficiency, working of the memory unit and their applications, the computers are classified as follows,
  • Mainframe Computer
  • Mini Computer
  • Micro or Personal Computer
  • Super Computer
Mainframe Computer:
The mainframe is a very large and is an expensive computer, capable of supporting hundreds or even thousands of users concurrently. Mainframe supports and executes many programs simultaneously. It is used in organizations for critical applications, bulk data processing, etc.,
 
IBM_System360_Mainframe.jpg
 
Mini Computer:
These are intermediate computers that fall between micro and mainframe computers in terms of size, speed and capacity. It is a multi-processing system capable of supporting up to 250 users simultaneously.
 
800px-TOSHIBA_minicomputer_(2747228884).jpg

Micro or Personal Computer:
A microcomputer or personal computer is a small, comparatively inexpensive computer with a microprocessor as its Central Processing Unit (CPU). It contains a microprocessor, memory and input/output (I/O) circuits mounted on a single Printed Circuit Board (PCB).
Based on their design, memory and efficiency Micro or Personal computers are classified into,
  • Desktop
  • Laptop
  • Tablet
450px-IBM_Personal_Computer_340.jpg
 
The Super Computer:
The Super computers are powerful computers commonly known as the high-performance as well as the fastest systems available at any given time. These computers have been primarily used for scientific and engineering work, which requires high-speed computations.
Examples:
  • Weather forecasting
  • Nuclear weapons and reactors
800px-Summit_Supercomputer_2018.jpg
Reference:
https://upload.wikimedia.org/wikipedia/commons/c/c0/IBM_System360_Mainframe.jpg
https://commons.wikimedia.org/wiki/File:TOSHIBA_minicomputer_(2747228884).jpg
https://commons.wikimedia.org/wiki/File:IBM_Personal_Computer_340.jpg
https://commons.wikimedia.org/wiki/File:Summit_Supercomputer_2018.jpg