Mastering Assembly Programming

Scale, index, base, and displacement

This is a very flexible addressing mode as it allows us to address memory in a manner similar to addressing data within arrays, which we are all familiar with. Despite the fact that this addressing mode is often referred to as scale/index/base (omitting the displacement part), we are not forced to make use of all of its elements at once, and we will further see that the scale/index/base/displacement scheme often gets reduced to base, base + index, or displacement + index. The latter two may come with or without scale. But, first of all, let's see who is who and which part represents what:

• Displacement: Technically, this is an integer offset relative to a certain segment base (DS by default).
• Base: This ...