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Basic I/O System (BIOS) Functions
5-2
ORGANIZATION OF THE BIOS
The BIOS portion of CP IM-86 resides in the topmost part of the operating system
(highest addresses), and takes the general form shown in Figure 5-2.
CS, DS, ES, SS:
Console
Command
Processor
and
Basic
Disk
Operating
System
CS
+
2500H:
BIOS Jump Vector
CS
+
253FH:
BIOS Entry Points
BIOS:
Disk
Parameter
Tables
U nini tialized
Scratch RAM
Figure 5-2
General CP/M-86 Organization
In order to implement CP IM-86 on the APC hardware, NEC has modified the
standard BIOS distributed by Digital Research, Inc. to create a BIOS which
performs the functions listed in Chapters 5 and 6. The cold start loader that loads
the CPM.syS into memory contains a simplified form of the BIOS, called the
LDBIOS (Loader BIOS).
It
loads CPM.SYS into memory at the location defined in
the CPM.SYS header (absolute address 0400H).
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