Assembly Language Statement

The layout of a machine instruction is part of the architecture of a processor chip. Without knowing the layout you can't tell what the instruction means. Even if you know the layout, it is hard to remember what the patterns mean and hard to write machine instructions.

A statement in pure assembly language corresponds to one machine instruction. Assembly language is much easier to write than machine language. Here is the previous machine instruction and the assembly language that it corresponds to:

machine instruction                             assembly language statement

0000 0001 0010 1011 1000 0000 0010 0000         add $t0,$t1,$t2

The instruction means: add the integers in registers $t1 and $t2 and put the result in register $t0. To create the machine instruction from the assembly language statement a translation program called an assembler is used.

Humans find assembly language much easier to use than machine language for many reasons.

• It is hard for humans to keep track of those ones and zeros.
• By using symbols programmers gain flexibility in describing the computation.
• Assembly language is a compact notation.

Enhanced assembly language includes additional convenience features. It has instructions (called pseudoinstructions) that correspond to several machine instructions.