6 - Assembly language programs

Abstract

Programming at machine code level using hand assembly is a tedious process, because it requires a programmer to spend much time looking up opcodes for each instruction, performing various calculations in binary or hexadecimal, and simultaneously keeping track of many different addresses. It is necessary to use a better method if serious program writing is contemplated, because hand assembly is time-consuming and error-prone. Such a method consists of writing programs at assembly language level, and using an assembler program to generate all necessary machine code for the microprocessor. The use of assembly language makes programs easier to follow. The initial stages in writing an assembly language program involve the preparation of source code. Source code consists of a sequence of the American standard code for information interchange (ASCII) characters that represent instruction mnemonics, symbolic addresses, and data for an assembly language program, and is stored as a disk file that is accessed by an assembler to generate the equivalent machine or object code.