| KEY | N | I | VAR | Short description | COMMON | GINIT |
| DEBU | 3 | M | IDEMIN | first event to debug. | /GCFLAG/ | 0 |
| IDEMAX | last event to debug | /GCFLAG/ | 0 | |||
| ITEST | print control frequency | /GCFLAG/ | 0 | |||
| GET | 20 | M | LGET | NGETnames of data structures tofetch (see Note) | /GCLIST/ | Blank |
| PRIN | 20 | M | LPRIN | NPRINuser keywords to print datastructure (see Note) | /GCLIST/ | Blank |
| RGET | 20 | M | LRGET | NRGETnames of data structures to fetchfrom RZ files (see Note) | /GCRZ/ | Blank |
| RSAV | 20 | M | LRSAVE | NRSAVEnames of data structures to savefrom RZ files (see Note) | /GCRZ/ | Blank |
| SAVE | 20 | M | LSAVE | NSAVEnames of data structures tosave (see Note) | /GCLIST/ | Blank |
| SWIT | 10 | I | ISWIT | user flags for debug | /GCFLAG/ | 0 |
Note: the user data records for I/O have no effect on the GEANT system, and the user is supposed to analyse them at run time and take corresponding action. For instance, a use of the PRIN data record could be the following:
CALL GLOOK('VOLU',LPRIN,NPRIN,IPRES)
IF(IPRES.NE.0) THEN
CALL GPVOLU(0)
ENDIF
All the names quoted here are given as 4-character strings in input and their ASCII equivalent is read into the corresponding variable. The same applies to the user lists of the following section.