Microprocessors recognize and operate in binary numbers.
The number of bits the microprocessor recognizes and processes at a time is called a word.
A group of eight bits is called a Byte.
A group of four bits is called a Nibble.
To communicate with a microprocessor we must give instructions in machine language(binary language). Each combination of bit patterns that have given a specific meaning is called an instruction.(operation code/ opcode)
It instructs the microprocessor to perform a specific function.
Since it is difficult to write instructions in binary(or hexadecimal), computer manufacturers have created English-like words to represent the binary instructions. Symbolic code for representing an instruction is called a mnemonic.
Programs written using these words(mnemonic) are called assembly language programs. Programs written in assembly language is translated into machine language using a program called an assembler.