Introduction

In the previous unit, we have discussed the 8086 microprocessor. We have discussed the register set, instruction set and addressing modes for this microprocessor. In this and two later units we will discuss the assembly language for 8086/8088 microprocessor. Unit 1 is the basic building block. which will help in better understanding of the assembly language. In this unit, we will discuss the importance of assembly language, basic components of an assembly program followed by discussions on the program developmental tools available. We will then discuss what are COM programs and EXE programs. Finally we will present a complete example. For all our discussions, we have used Microsoft Assembler (MASM). However, for different assemblers the assembly language directives may change. Therefore, before running an assembly program you must consult the reference manuals of the assembler you are using.

Objectives

After going through this unit you' should be able to:

• define the need and importance of an assembly program
• define the various directives used in assembly program
• write a very simple assembly program with simple input - output services; 
• define COM and EXE programs; and
• differentiate between COM and EXE programs.