Naming conventions for SVC routines

SVC routines are load modules which are named as follows:

The routines for SVC types 1, 2 and 6 are named IGCxxx, where xxx is the SVC number (decimal).
The routines for SVC types 3 and 4 are named IGC00xxx, where xxx is the SVC number.
If a type 4 SVC routine calls for multiple SVC loads, the naming convention is to identify each load by increasing 00 by one. For example, IGC03xxx indicates the third module loaded within a type 4 SVC routine.

For types 3 and 4 SVC routines, the internal format of the SVC number (xxx) is zoned decimal with a four-bit sign code (1100) in the four high-order bits of the low order byte. Any low-order digit in a type 3 or 4 SVC number that is between 1 and 9 will be an EBCDIC character between A and I in the load module name. For example, the load module name for SVC 51 (X'33') would be IGC0005A because the low order byte is 1100 0001, or A in zoned decimal. A low-order zero in the SVC number corresponds to a hexadecimal C0 in the load module name.

ESR type 3 routines have names in the format IGX00nnn, where nnn is the decimal code placed in register 15 when SVC 109 is issued.