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Chapter 1
CP IM-86 System Overview
CP/M-86 GENERAL CHARACTERISTICS
CP/M-86 consists of all the facilities of CP/M-80 with additional features to
account for increased processor address space of up to one megabyte (1,048,576) of
main memory. CP/M-86 maintains file compatibility with all previous versions of
CP/M. It uses the file structure of CP/M Version 2, allowing as many as sixteen
drives with up
tb
eight megabytes on each drive. CP/M-80 and CP/M-86 programs
may exchange files without any modification to the file formats.
CP/M-86 resides in the file CPM.SYS, which is loaded into memory by a cold start
loader during system initialization. The cold start loader resides on the first two
tracks of the system disk. CPM.SYS contains three program modules: the Console
Command Processor (CCP), the Basic Disk Operating System (BDOS), and the
Basic Input/Output System (BIOS). The BIOS distributed on the CP/M system
diskette has been configured for the APC and is called the Customized BIOS, or
CBIOS. It is made up of three parts: the standard BIOS, the APC escape sequence
functions, and the extended BIOS. The CCP and BDOS portions occupy approxi-
mately 10K bytes, and the BIOS is approximately 22 bytes. The operating system
executes in memory above the reserved interrupt locations. The remainder of the
address space may be partitioned into eight non-contiguous regions, as defined in a
BIOS table. Unlike CP/M-80, CP/M-86 does not allow the CCP area to be used as a
data area subsequent to transient program load. All CP/M-86 modules remain in
memory at all times and are not reloaded at a warm start.
Like CP/M-80, CP/M-86 loads and executes memory image files from disk.
Memory image files are preceded by a header record, defined in Chapter 3, which
provides information required for proper program loading and execution. Memory
image files under CP/M-86 are identified by the CMD file type exte.nsion.
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