Combining Segments

A segment is a code or data block created by the compiler or assembler from your source code. There are two basic types of segments: absolute and relocatable.

• An absolute segment resides at a fixed memory location and may not be relocated or moved by the linker. Absolute segments do not have names and are not combined with other segments. They are copied directly to the output file.
• A relocatable segment has a name and a type (as well as other attributes shown in the table below). Two or more relocatable segments with that have the same name are called partial segments. They are considered to be part of the same segment and are combined by the linker (even if they are created in separate source files).

While processing program modules, the linker produces a table of all segments. The linker stores the segment name, type, location method, length, and base address and uses this information to combine partial relocatable segments. When combining segments, the following rules are observed:

1. All partial segments that share a common name must have the same memory class. An error occurs if the types do not correspond.
2. The length of the combined segments must not exceed the length of the physical memory area.
3. The location method for each of the combined partial segments must correspond.

The following segment attributes are used to determine how to link, combine, and locate code or data in a segment.