The Z80 restart instruction, or
RST, can be used instead of a B_CALL for some system entry points. The advantage is that using the RST instruction takes only one byte, instead of the three bytes required for a B_CALL, and is very quick when compared with the relatively large overhead inherent of a B_CALL.
All the RST routines work exactly the same as the corresponding B_CALLs:
rOP1ToOP2 EQU 08h rFindSym EQU 10h rPushRealO1 EQU 18h rMov9ToOP1 EQU 20h rFPAdd EQU 30h
You cannot define your own RSTs; they are part of the operating system.
rst 00 is the OS reset rst 28h is BCALL rst 38h is the interrupt routine