Professional Assembly Language

Chapter 10. Working with Strings

For humans, written communication is crucial. Unfortunately, computers were not specifically designed for ease of communication with humans. Most high-level languages provide specific functions for helping programmers write programs to interact with humans. As an assembly language programmer, you do not have the luxury of these functions. It is up to you to code your programs to interact with humans in their own language.

The use of strings helps programs communicate with humans in their own language. While using strings is not a simple matter in assembly language programming, it is not impossible. This chapter guides you through working with strings. The first section discusses the instructions used to move strings around in memory by copying them from one memory location to another. The next section shows how, similar to integers, strings can be compared for equality. The last section describes the instructions that are used to scan strings for a search character or character string. This feature comes in handy when searching for specific characters within text.

Note that the string instructions presented in this chapter also can be applied to nonstring data. Moving, modifying, and comparing blocks of numerical data can also be accomplished using the IA-32 string instructions.

Moving Strings

One of the most useful functions when dealing with strings is the capability to copy a string from one memory location to another. If you remember from Chapter ...