When to use COMP,COMP-3 variables?

[KavalJeet]

Hi ,

I'm not sure what answer is best suitable when someone asks :: When should we go for COMP,COMP-3 variables? What advantage these variables have over Usage DISPLAY variables other than Memory size?

[Robert Sample]

COMP and COMP-3 variables are best when doing arithmetic with the variables. COMP works better for indexing / subscripting while COMP-3 is typically how COBOL does mathematical operations. However, the difference between these variables and zoned decimal variables will be negligible unless you are doing BILLIONS of operations in your program.

[KavalJeet]

However, the difference between these variables and zoned decimal variables will be negligible unless you are doing BILLIONS of operations in your program.

What difference you're talking about here?

[Robert Sample]

Using COMP variables for subscripts and COMP-3 variables for arithmetic is SLIGHTLY more efficient (less CPU time) than zoned decimal. However, to see any CPU difference in COMP / COMP-3 versus zoned decimal, you have to be doing a LOT of calculations / subscripts. In general, unless you have a known issue with performance, you could code your program without any COMP / COMP-3 variables and you would not see any difference in CPU time.

[KavalJeet]

Thanks you Robert.

In a recent interview I told the same to the interviewer but he asked leave it and in general how the "amount filed" will be defined comp or comp-3...

[Robert Sample]

An amount field implies accumulation and / or arithmetic so use COMP-3.