6
Instruction Set and
Assembly Language
Programming
This chapter deals with instruction set in general and details of instruction sets of the three
processors introduced in Chapter 5. The chapter is concluded through some discussions
on assembly language programming involving assemblers and also taking care of two
advanced processors, 80386 and Pentium 4. After completion of this chapter, the reader
would know about
R Basic characteristics of instructions with formats and elds
R Different types of addressing modes
R Assembly language programming details
R Assembler characteristics.
R Instruction details of Intel 8085, 8086, 8051, 80386 and Pentium 4.
C HAPTER OBJECTIVES
6.1 INTRODUCTION
In Chapter 5, we have discussed about processors, in general, and three example processors, namely
8085, 8086 and 8051, in particular. Before its conclusion, we have also introduced two advanced pro-
cessors, namely 80386 and Pentium 4. The discussions were restricted within their hardware character-
istics, mainly related with their architectural and some organizational issues.
However, for a computer, the hardware alone is unproductive and meaningless, as individually it can-
not accomplish anything, just like any bird with a single wing. Every computer (or the processor inside)
needs some software in the form of a set of instructions to be executed by it. Note that both hardware as
well as software are equally important to achieve the goal in any processor based system or computer.
We are yet to imagine any computer with only hardware or with only software.
For developing utility programs or user programs, every processor offers its own instruction set.
These instructions can perform very primitive operations and dependent on the architecture of that
processor. The software developed for one processor generally does not work in another proces-
sor, leaving aside the backward compatible cases of some processor families (like Pentium 4 and
8086). In this chapter, we shall discuss about some of the details of these instruction sets and sample
instructions.
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