Joined: 08 Aug 2005 Posts: 3 Location: Chennai, Tamil NAdu, INDIA
Can anyone explain me how to choose which COMP (COMP1,COMP2.....)data types to choose for different requirements.
How to calculate the size of the var declared as any of the COMP data types? This is a interview question.
Depending on the requirement and where the var will used, the data types are used. For eg calculations are faster if u declare comp. Also memory utilization is more in boundaries in case of COMP compared to COMP-3.
Specified for binary data items. Such items have a decimal equivalent
consisting of the decimal digits 0 through 9, plus a sign. Negative
numbers are represented as the two's complement of the positive number
with the same absolute value.
The amount of storage occupied by a binary item depends on the number
of decimal digits defined in its PICTURE clause:
Digits in PICTURE Clause Storage Occupied
1 through 4 2 bytes (halfword)
5 through 9 4 bytes (fullword)
10 through 18 8 bytes (doubleword) │
The leftmost bit of the storage area is the operational sign.
Specified for internal decimal items. Such an item appears in storage
in packed decimal format. There are 2 digits for each character
position, except for the trailing character position, which is
occupied by the low-order digit and the sign. Such an item can
contain any of the digits 0 through 9, plus a sign, representing a
value not exceeding 18 decimal digits.
The sign representation uses the same bit configuration as the 4-bit
sign representation in zoned decimal fields (see Table 12 in
topic 184.108.40.206 and Table 13 in topic 220.127.116.11).
COMPUTATIONAL or COMP
Representation of the COMPUTATIONAL phrase is system-dependent and is
normally assigned to representations that yield the greatest
efficiency when arithmetic operations are performed on that system.
For the VS COBOL II compiler, the COMPUTATIONAL phrase is synonymous
COMPUTATIONAL-1 or COMP-1
Specified for internal floating-point items (single precision).
COMP-1 items are 4 bytes long. The sign is contained in the first bit
of the leftmost byte and the exponent is contained in the remaining 7
bits. The last 3 bytes contain the mantissa.
COMPUTATIONAL-2 or COMP-2
Specified for internal floating-point items (double precision).
COMP-2 items are 8 bytes long. The sign is contained in the first bit
of the leftmost byte and the remaining 7 bits contain the exponent.
The remaining 7 bytes contain the mantissa.
COMPUTATIONAL-3 or COMP-3 (internal decimal)
For VS COBOL II, this is the equivalent of PACKED-DECIMAL.
COMPUTATIONAL-4 or COMP-4 (binary)
For VS COBOL II this is the equivalent of BINARY.