Segments

Objects generated by the Cx51 and Intel PL/M-51 compilers are stored in segments, which are units of code or data memory. Segments may be absolute, meaning they are located at a specific address, or relocatable, meaning that the linker assigns them a final address (in accordance with certain restrictions specified in the segment definitions). Relocatable segments have a type and a name unlike absolute segments.

Segment names include a module_name which is the name of the source file in which the object is declared excluding 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 to and stored in uppercase.

Each segment name has a prefix (or in case of PL/M-51 a suffix) that corresponds to the memory type used for the segment. The prefix is enclosed in question marks (?). Following is a list of standard segment name prefixes.

Segment Prefix	Memory Class	Description
?BA?	DATA	Bit-addressable data in internal data memory
?BI?	BIT	Bit data in internal data memory
?CO?	CONST	Constant data in program memory
?DT?	DATA	DATA memory
?FC?	HCONST	Far constant data in program memory
?FD?	HDATA	HDATA memory for far variables
?ID?	IDATA	IDATA memory
?PD?	XDATA	Paged data in XDATA memory
?PR?	CODE	Executable program code
?PR?	ECODE	Executable program code in far memory
?XD?	XDATA	XDATA memory

Refer to Segment Naming Conventions in the Cx51 Compiler User's Guide for more information about segment names.