COMP is Binary storage format. The COMP field can be defined as
01 WS-COMP-FIELD PIC 9(04) COMP.
The Storage taken by COMP field depends on length of the field.
0 to 4 field length – 2 bytes
5 to 9 field length – 4 bytes
10 to 18 field length – 8 bytes

COMP-1 is single precision floating point. COMP-1 uses 4 bytes of storage. No
picture clause should be given while defining the COMP-1 fields.

01 WS-COMP-1-FIELD USAGE IS COMP-1.

COMP-2 is double precision floating point. COMP-2 uses 8 bytes of storage. No
picture clause should be given while defining the COMP-2 fields.

01 WS-COMP-2-FIELD USAGE IS COMP-2.

COMP-3 is packed decimal format. COMP-3 uses storage depends on the length of
the field. Integer of ((n/2)+1). Sign is stored in the last nibble of storage.

01 WS-COMP-3-FIELD PIC S9(07) USAGE IS COMP-3.
Here WS-COMP-3-FIELD occupies (integer of (7/2) +1)) = 4 bytes.