Input/Output Control System

IOCS supported several classes of I/O equipment

• Disk drives
• Tape drives
• Unit record equipment. The record length was dictated by the physical media, which were
  • Lines of print on paper
  • Punched 80-column[lower-alpha 1] cards

Some services offered by IOCS were not needed by all applications, e.g., checkpoints, label processing. An IOCS program must identify the particular devices types and services it uses. A 7070 IOCS program must specify one or more DIOCS[7]^: 16–19[15]^: 22–25 statements:[lower-alpha 2]

<nowiki/>
              11   22
     6        56   01
     GENERAL   DIOCS''general parameters''
     TAPE      DIOCSD729,''tape parameters''
     DISK      DIOCSD1301,''disk parameters''
     END       DIOCS

These declarative statements identify index registers reserved for the use of IOCS, indicate channels used, indicate whether the program is to coexist with SPOOL and provide processing options. The END DIOCS statement causes the assembly of IOCS unless a preassembled version is requested. The first (general) form is omitted when the D729 form is used.

In some other IOCS packages similar functions are provided by control cards.

An IOCS program must create a control block for each file, specifying information unique to the file. For 7070 IOCS these are entries in the File Specification Table for tape files, each of which is generated by a DTF[7]^: 19–26[15]^: 26–28 statement, or separate control blocks generated by DDF[8]^: 31–37[15]^: 29–30 or DUF[7]^: 44–47[15]^: 31–33 statements.

              11   22
     6        56   01
               DTF  OUT
     FCHANNEL       2
               ...  ...
     DAFILE    DDF
     IODEVICE       5
     DREFMODE       4
               ...  ... 
               DUF  CONSFILE,1,4,CARDRDW,CARDIX,CONSEOF,CONSERR

In some other IOCS packages similar functions are provided by control cards.

The above code defines a tape file on channel 1 called OUT, a sequential 1301/1302 disk file called DAFILE and a card file called CONSFILE.

Any IOCS program must specify the actions that it wishes to perform. In 7070 IOCS this is done with processing macros.[lower-alpha 2]

              11   22
     6        56   01
               OPEN CONSFILE,OUT
     LOOP      GET  CONSFILE
               PUT  OUT
               B    LOOP
     CONSEOF   CLOSECONSFILE,OUT

In some other IOCS packages similar functions are provided by explicit subroutine calls.