What is 'assembler'? Briefly explain various steps of assembling.

Assembler is a computer program, known as language translator, which is used to translate program written in assembly language into machine language. The translated program is called an object program. Assembler checks each instruction for its correctness and generates diagnostic messages, if there are mistake in program. Various steps of assembling are: To input source program in Assembly Language through an input device; Assembling the source code into an object file; Linking the object file with other modules or libraries into an executable program; Loading the program into memory; To execute the program.