System information

File expansion is achieved by providing up to 512 logical file extents, where each logical extent
contains 16K bytes of data. CP/M 2 is structured, however, so that as much as 128K bytes of
data are addressed by a single physical extent, corresponding to a single directory entry,
iuaintaining compatibility with previous versions while taking advantage of directory space.
If CP/M is being tailored to a computer system for the first time, the new BIOS requires some
simple software development and testing. The standard BIOS is listed in Appendix A and can be
used as a model for the customized package. A skeletal version of the BIOS given in Appendix B
can serve as the basis for a modified BIOS.
In addition to the BIOS, you must write a simple memory loader, called GETSYS, which brings
the operating system into memory. To patch the new BIOS into CP/M, you must write the
reverse of GETSYS, called PUTSYS, which places an altered version of CP/M back onto the
disk. PUTSYS can be derived from GETSYS by changing the disk read commands into disk
write commands. Sample skeletal GETSYS and PUTSYS programs are described in Section 6.4
and listed in Appendix C.
To make the CP/M system load automatically, you must also supply a cold start loader, similar to
the one provided with CP/M, listed in Appendixes A and D. A skeletal form of a cold start loader
is given in Appendix E, which serves as a model for the loader.
6.1 Introduction CP/M Operating System Manual
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