The System Services provide a program with the ability to terminate and resart CPM as well as check the version of the CPM operating system.
| Function 0: System Reset | ||
| Register | Value | |
|---|---|---|
| Entry | C | 00H |
| Return | (none) | |
The System Reset function returns control to the CP/M operating system at the CCP level. The CCP reinitializes the disk subsystem by selecting and logging-in disk drive A. This function has exactly the same effect as a jump to location BOOT.
| Function 12: Return Version Number | ||
| Register | Value | |
|---|---|---|
| Entry | C | 0CH |
| Return | HL | Version Number |
Function 12 provides information that allows version independent programming. A two-byte value is returned, with H = 00 designating the CP/M release (H = 01 for MP/M) and L = 00 for all releases previous to 2.0. CP/M 2.0 returns a hexadecimal 20 in register L, with subsequent version 2 releases in the hexadecimal range 21, 22, through 2F. Using Function 12, for example, the user can write application programs that provide both sequential and random access functions.