Intel iAPX 86 User Manual page 101

iAPX 86,88 Absolute Object File Formats
iAPX 86,88 Family Utilities
A-2
Module Identification
In order to determine that a file contains an object program, a module header record
will always be the first record in a module. There are two kinds of header records
and each provides a module name. The addirional functions of the header records
are explained below.
A module name may be generated during
OnE:
of two processes: translation or link-
ing. A module that results from translation is called a T-MODULE. AT-MODULE
will have a T-MODULE HEADER RECORD (THEADR). A name may be
provided in the THEADR record by a translator. This name is then used to identify
the progenitor of all debug information found in the T-MODULE. The name may
be null, i.e., of length zero.
A module that results from linking and locating is called an L-MODULE. An
L-MODULE will always have an L-MODULE HEADER RECORD (LHEADR) or
an R-MODULE HEADER RECORD (RHEADR). In the LHEADR or RHEADER
record a name is also provided. This name is available for use to refer to the module
without using any of its constituent T-MODULE names. An example would be two
T-MODULES, A and B, linked together to form L-MODULE C. L- MODULE C
will contain two THEADR records and will begin with an LHEADR record with the
name C provided by the linker as a directive from the user. The L- MODULE C can
be referred to by other tools such as the library manager without having to know
about the originating module's names, yet the originating module's names are
preserved for debugging purposes.
Module Attributes
In addition to a name, a module may have the attribute of being a main program as
well as having a specified starting address.
If a module is not a main module yet has a starting address, then this value has been
provided by a translator, possibly for debugging purposes. A starting address
specified for a non-main module could be the entry point of a procedure, which may
be loaded and initiated independent of a main program.
Physical Segment Definition
A module is defined as a collection of data bytes defined by a sequence of records
produced by a translator. The data bytes represent contiguous regions of memory
whose contents are determined at translation tiime.
Physical Segment Addressability
The 8086 addressing mechanism provides segment base registers from which a 64K
byte region of memory, called a Frame, may be addressed. There is one code seg-
ment base register (CS), two data segment basE: registers (OS, ES), and one stack seg-
ment base register (SS).