TypeCobolTypesNutshell

Types in a Nutshell

The problem

With Cobol 85, there is no simple way to reuse structure of data across different programs. I can use a COPY, but this doesn’t work well if I need to use a structure with different data level.

Ex:

01 Person
   05 BirthDate.
      10 BirthDate-Year  pic 9(04).
      10 BirthDate-Month pic 9(02).
      10 BirthDate-Day   pic 9(02).
   05 LastModificationDate.
      10 LastModificationDate-Year  pic 9(04).
      10 LastModificationDate-Month pic 9(02).
      10 LastModificationDate-Day   pic 9(02).

If my date format must evolve, I need to modify all my variables named something like 'Date' one by one.

Prefix and length of variable name

If I use the variable parent’s name, I’ll end up with very long variable name. As Cobol 85 limit it to 30 characters (at least on Z/OS), I’ll be limited very quickly.

It’d be great to avoid to reuse the variable parent’s name and still distinguish clearly inside the code to what I refer.

The need

Reuse structure of data across different programs.
Avoid to write the prefix
Be sure that a structure is modified as a whole

The solution : Type

TypeCobol syntax (almost like Cobol 2002)	Translation into Cobol 85
01 Person TYPEDEF STRICT. 05 Id pic 9(05). 05 lastName pic X(30). 05 FirstName pic X(30). 05 BirthDate pic X(08).	Define a type `Person`. Levels will be renumbered when used as a type
01 myPerson TYPE Person.	01 myPerson. 02 Id pic 9(05). 02 lastName pic X(30). 02 FirstName pic X(30). 02 BirthDate pic X(08).
01 myPerson type Person. 01 myPerson2 type Person. move myPerson to myPerson2	*Ok because myPerson is of the same type as myPerson2 move myPerson to myPerson2
01 txtZone pic X. 01 myPerson type Person. move txtZone to myPerson	It doesn’t compile because txtZone isn’t of the same type as myPerson.
01 txtZone pic X. 01 myPerson type Person. move UNSAFE txtZone to myPerson	It’s allowed because the UNSAFE keyword is here to tell TypeCobol compiler to not control type. As a developer it’s my responsibility to be sure that the content of txtZone match the description of myPerson.
01 CarInsurance. 05 firstDriver type Person. 05 SecondDriver type Person.	01 CarInsurance. 05 firstDriver. 06 Id pic 9(05). 06 lastName pic X(30). 06 FirstName pic X(30). 06 BirthDate pic X(08). 05 SecondDriver 06 Id pic 9(05). 06 lastName pic X(30). 06 FirstName pic X(30). 06 BirthDate pic X(08).