BIT:
The computer works on the basis of “on” or “off” electronic pulses. Passing of a pulse represents 1 and blocking of a pulse represents 0. Bit is the smallest unit of information, normally any one of the binary digits i.e., 0 or 1. The word bits is derived from the term Binary Digit. A group of bits representing data or instructions that form the basis unit of computer is called a word. A group of four bits is called Nibble.
Byte:
A computer word is defined in terms of bytes. A word may be formed using two or more bytes, the most common being the four-byte combination in most computers. A byte refers to a group of bits used to designate a single alphanumeric or special character. The size of memory is specified in terms of bytes. Byte is made of eight bits.
Kilobyte:
Kilobytes means 1000 bytes. K stands for 1000 or kilo locations or more preciously K stand for 2 to the power 10 or 1024. The memory location of 640KB = 640*1024=655,360 bytes.
Megabyte:
Megabyte means one million bytes. One floppy contain 1.2MB = 1.2*1024**1024 bytes= 1,258,292 bytes. Therefore approximately 1 MB= 1,000,000 bytes.
Gigabyte:
1024 Megabytes form one Gigabyte.