DFHMDF is used to define a field with its characteristic in a map. The field name is mentioned against which DFHMDF macro is coded. This field name is used inside the program. We do not write field name against constant field which we do not want to use inside the program. There can be any number of DFHMDF within DFHMDI. Some of the important operands of DFHMDF are below:
It has two arguments that decided the position of the field. The two arguments are line and column. It is the position where the attribute byte of the field starts.
So if you code POS = (1,1), the attribute byte for that field is on line 1 in column 1, and the actual data starts in column 2.
The length of the field is coded here. It excludes the attribute character.
All the input and output fields are prefixed by one byte attribute field that defines the attributes of the field. Some of the attributes are:
Mutually exclusive parameters that define the type of the field.
UNPROT is coded for input and input-output fields.
PROT is coded for output and stopper fields.
ASKIP is coded for screen literals and skipper fields. The cursor automatically skipped to next field and so you cannot enter data into skipper field.
0-9,Period and – are the only allowed characters.
Mutually exclusive parameters that define the intensity of the field.
Insert Cursor. Cursor will be positioned on display of map. If IC is specified in more than one field of a map, the cursor will be placed in the last field.
Independent of whether the field is modified or not, it will be passed to the program. MDT is set for the field.
RIGHT is the default value. Code LEFT for numeric fields.
It defines the Picture clause of the symbolic map in COBOL and useful for numeric field editing.
The default value of the field is coded here. When the MAP is sent, this value will appear in the field. The constant information like TITLE is coded using INITIAL keyword of field definition.
To avoid data traffic, these constant information fields should not be coded without LABEL parameter. If there is no LABEL parameter, then symbolic map will not generated for those fields as they are unnamed fields.
The following example shows how to code a field definition,
DFHMDF POS = (01,01), X
LENGTH = 18, X
INITIAL = ‘SAMPLE CICS SCREEN’, X
ATTRB = (PROT,NORM)
STDID DFHMDF POS = (01,70), X
LENGTH = 08, X
ATTRB = (PROT,NORM) |
If you have any doubts or queries related to this chapter, get them clarified from our Mainframe experts on ibmmainframer Community!