Objects generated by the C51 compiler (program code, program data, and constant data) are stored in segments which are units of code or data memory. A segment may be relocatable or may be absolute. Each relocatable segment has a type and a name. This section describes the conventions used by C51 for naming these segments.
Segment names include a module_name. The module_name is the name of the source file in which the object is declared and excludes the drive letter, path specification, and file extension. In order to accommodate a wide variety of existing software and hardware tools, all segment names are converted and stored in uppercase.
Each segment name has a prefix that corresponds to the memory type used for the segment. The prefix is enclosed in question marks (?). The following is a list of the standard segment name prefixes:
| Segment Prefix |
Data Type |
Description |
| ?PR? |
code |
Executable program code |
| ?CO? |
code |
Constant data in program memory |
| ?XD? |
xdata |
External data memory |
| ?DT? |
data |
Internal data memory |
| ?ID? |
idata |
Indirectly-addressable internal data memory |
| ?BI? |
bit |
Bit data in internal data memory |
| ?BA? |
bdata |
Bit-addressable data in internal data memory |
| ?PD? |
pdata |
Paged data in external data memory |