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CP/M-86 System Overview
1-2
Unlike CP/M-80, CP/M-86 does not use absolute locations for system entry or
default variables. The BDOS entry takes place through a reserved software inter-
rupt. Entry to the BIOS is provided by a new BDOS call. Entry to the extended
BIOS is made directly through an interrupt vector. Two variables maintained in low
memory under CP/M-80, the default disk number and I/O Byte, are placed in the
CCP and BIOS respectively in CP/M-86. Dependence on absolute addresses is
minimized in CP/M-86 by maintaining inital base page values, such as the default
File Control Block and default command buffer, in the transient program data
area.
Utility programs such as ED, PIP, STAT, and SUBMIT operate in the same manner
under CP/M-86 and CP/M-80. DDT-86 allows interactive debugging of 8086
machine code. ASM-86 allows assembly language programming and development
for the 8086 using Intel-like mnemonics.
CP/M-86 includes two utilities that replace equivalent CP/M-80 utilities .
• GENCMD (Generate CMD file) replaces the LOAD program ofCP/M-80.
It
converts the hex files produced by ASM-86 or Intel utilities into memory
image format suitable for execution under CP/M-86 .
• LDCOPY (Loader Copy) replaces the SYSGEN utility used under
CP/M-80.
It
is used to copy the cold start loader from a system disk for
replication.
Several terms used throughout this manual are defined in Table 1-1.
A group consists of segments that are loaded into memory as a single unit. Since a
group may consist of more than 64 bytes, it is the responsibility of the application
program to manage segment registers when accessing code or data beyond the first
64K segment.
CP/M-86 supports eight program groups: the code, data, stack, and extra groups,
and four auxiliary groups. When a code, data, stack, or extra group is loaded,
CP/M-86 sets the respective segment register (CS, DS, SS or ES) to the base of the
group. CP/M-86 can also load four auxiliary groups. A transient program manages
the location of the auxiliary groups using values stored by CP/M-86 in the user's
base page.
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