Relationship between MFS control blocks and screen format

Use the control blocks in the MFS source language to define the formats that you see at the device.

The standard way for an end-user or operator to receive an initial format is to request it with a /FORMAT command, specifying the name of a MOD. In the following code example, the label on the MOD is PAYDAY. This MOD contains the parameter SOR=PAYF, which points to a device output format, or DOF, with the same label.

The initial DOF also becomes the format for device input. Therefore, if you specify DIV TYPE=INOUT in the DOF, a device input format (DIF) is also generated. In the sample code, PAYF is both a DOF and a DIF, since it also describes the format of the next input. The final output message can be displayed with a format that is specified for output only and no DIF is generated.

Both the MOD and the MID point to the same DOF, thus establishing the relationship between device-related and message-related control blocks.

For output, MFS moves fields defined in a MOD to fields on the screen defined by a DOF. When a field definition is coded (MFLD) in a MOD, it is given a label. The same label is used in the coding of the device field (DFLD) in the DOF, defining where the field appears on the screen.

MFS moves data fields from output messages to screen fields; this is referred to as mapping. For input, MFS moves modified screen fields to data fields in the input message for the program by mapping identically labeled fields in the DIF and MID.

For more detailed information on specifying these control blocks, see IMS Version 15.5 Database Utilities.

The MFS control blocks are generated from the source statements like those in the following code example during execution of the MFS Language utility. The control blocks are stored in the various MFS libraries.

The sample code is designed for a 3270 display.

PAYF     FMT
         DEV       TYPE=(3270,2),FEAT=IGNORE,DSCA=X'00A0'
         DIV       TYPE=INOUT
         DPAGE     CURSOR=((5,15))
         DFLD      '**********************',POS=(1,21)
         DFLD      '*  EMPLOYEE PAYROLL  *',POS=(2,21)
         DFLD      '**********************',POS=(3,21)
         DFLD      'FIRST NAME:',POS=(5,2)
FNAME    DFLD      POS=(5,15),LTH=16
         DFLD      'LAST NAME:',POS=(5,36)
LNAME    DFLD      POS=(5,48),LTH=16
         DFLD      'EMPLOYEE NO:',POS=(7,2)
EMPNO    DFLD      POS=(7,16),LTH=6
         DFLD      'SOC SEC NO:',POS=(9,2)
SSN      DFLD      POS=(9,15),LTH=11
         DFLD      'RATE OF PAY: $',POS=(11,2)
RATE     DFLD      POS=(11,17),LTH=9
         DFLD      'INPUT:',POS=(16,2)
INPUT    DFLD      POS=(16,10),LTH=30
         FMTEND

PAYIN    MSG       TYPE:INPUT,SOR=(PAYF,IGNORE)
         SEG
         MFLD      'PAYUP '     SUPPLIES TRANCODE
         MFLD      LNAME,LTH=16
         MFLD      FNAME,LTH=16
         MFLD      EMPNO,LTH=6
         MFLD      SSN,LTH=11
         MFLD      RATE,LTH=9
         MFLD      INPUT,LTH=30,JUST=R,FILL=C'0'
         MSGEND

PAYDAY   MSG       TYPE:OUTPUT,SOR=(PAYF,IGNORE)
         SEG
         MFLD      LNAME,LTH=16
         MFLD      FNAME,LTH=16
         MFLD      EMPNO,LTH=6
         MFLD      SSN,LTH=11
         MFLD      RATE,LTH=9
         MFLD      INPUT,LTH=30,JUST=R,FILL=C'0'
         MSGEND