Register linkage conventions

ISPF uses standard linkage conventions:

SELECT PGM(program-name)
REGISTER

CONTENTS

1

Points to the address of the parameter data (from the PARM keyword) field (half-word length) followed by the data

2 - 12

Not used

13

72-byte save area

14

Return address

15

Entry address / Return code on exit
ISPF EXITS / Call to ISPLINK
REGISTER

CONTENTS

1

On entry, points to a parameter list; each address in the list in turn points to a parameter. On return to the caller of ISPLINK, the user's parameter list starts at the second parameter. ISPF has inserted a parameter in front of the user's parameters for ISPF use.

2 - 12

Not used

13

72-byte save area

14

Return address

15

Entry address / Return code on exit
SELECT CMD(cmdname) where cmdname is a program that is attached as a command processor by ISPF:
REGISTER

CONTENTS

1

Points to a CPPL (Command Processor Parameter List) which is a list of four addresses that point respectively to: Command buffer, UPT, PSCB, ECT. See the TSO programming services manual for descriptions of these parameters.

2 - 12

Not used

13

72-byte save area

14

Not applicable

15

Return code on exit

Usually when an abend occurs within ISPF code, register 12 points to the entry point of the abending CSECT.