Professional Assembly Language

Chapter 7. Using Numbers

Representing and working with numbers is a large part of any assembly language program. Almost every application uses some type of numerical data to process information. Just like high-level languages, assembly language can represent numbers in many different formats. If you are used to programming in C or C++, you are familiar with defining specific data type variables. Each time the variable is present, the compiler knows what type of data it represents. In assembly language programming, this is not always the case. Values stored in memory or registers can be interpreted as many different data types. It is your job as the assembly language programmer to ensure that the stored data is interpreted in the proper manner using the proper instructions. The purpose of this chapter is to describe the different number formats available, and demonstrate how they are used in assembly language programs.

The chapter starts off by describing the integer data types, unsigned and signed. After that, a discussion on the special Binary Coded Decimal data type is presented, along with examples of using it in programs. After that, floating-point numbers are tackled, including both the standard single and double-precision floating-point formats, and the Intel double-extended and packed single- and double-precision formats. Finally, some of the Intel instructions used to convert numeric data types from one format to another are presented.

Numeric Data Types

There are numerous ...