There are five generations of computers defined by changes in hardware technology over time. Generations now include both hardware and software that make up a computer system. The basic parts of a computer are the central processing unit, memory, input/output devices, and secondary storage. Computer memory is measured in bits, bytes, nibbles, and words, with a byte being the smallest unit that can represent data. System software manages computer activities and application software performs specific tasks for users.

1. COMPUTER SCIENCE

2. Generations of Computer​
Generation in computer terminology is a change in technology a computer is/was
being used. Initially, the generation term was used to distinguish between varying
hardware technologies. Nowadays, generation includes both hardware and
software, which together make up an entire computer system. ​
There are five computer generations known till date. Each generation has been
discussed in detail along with their time period and characteristics. In the following
table, approximate dates against each generation has been mentioned, which are
normally accepted.​

4. Different types of computers
When most people hear the word computer, they think of a personal computer such as a
desktop or laptop. However, computers come in many shapes and sizes, and they perform
many different functions in our daily lives. When you withdraw cash from an ATM, scan
groceries at the store, or use a calculator, you're using a type of computer.
Desktop computers
Laptop computers
Tablet computers
Servers
Other types of computers

6. Basic Parts of a Computer
The basic parts of a computer are:
● The Central processing Unit
● Arithmetic and Logic Unit
● Control Unit
● Main Memory (RAM)
● Input devices
● Output devices
● Secondary storage (hard-disks, floppy disks etc.)

8. Computer Memory Units
Bit (Binary Digit)
A binary digit is logical 0 and 1 representing a passive or an active state of a component in
an electric circuit.
Nibble
A group of 4 bits is called nibble.
Byte
A group of 8 bits is called byte. A byte is the smallest unit, which can represent a data item
or a character.
Word
A computer word, like a byte, is a group of fixed number of bits processed as a unit, which
varies from computer to computer but is fixed for each computer.

10. System software and Application software
System software:
A system software manages all the activities of the computer. It manages input
and output operations, errors, etc., in a computer. It automatically starts running
when the computer is turned on.
Application software:
In a computer, there are some software which are designed to perform a single
task. These software are called Application software.