What is the difference between COMP and COMP-3?

[Pragya]

Hi,

What is the difference between COMP and COMP-3? How can we display them.

My answer was one is binary and other is packed decimal. But Interviewer was not very happy.

I was not sure on how to display them, can someone please tell?

[Priya]

You need to move them to edit characters to display them. COMP is of 2 bytes and COMP-3 is 8 bytes. And COMP has sign over punched at it last nibble where as for COMP-3 it will take extra half byte for sign.

[Akatsukami]

COMP-3 is not eight bytes; it is ROUND((number-of-digits+1)/2) bytes.

[Robert Sample]

Priya, you managed to mess up pretty much EVERYTHING you said. A COMP variable may be 2 bytes or 4 bytes or 8 bytes depending upon the PICTURE. The sign, if used (COMP variables can be unsigned), is the first bit of the value.

And COMP has sign over punched at it last nibble

No, you have described Zoned Decimal signs -- NOT COMP! And as pointed out a COMP-3 variable length depends upon the PICTURE digits.

123 as a 2-byte COMP variable will be X'007B'. 123 as PIC S9(03) COMP-3 variable will be X'123C'. 123 as a 3-byte signed zoned decimal variable will be X'F1F2C3'. All of this is CLEARLY explained in the Enterprise COBOL Language Reference manual.

Also, you can use DISPLAY -- but signed values may require interpretation since the values will be converted to zoned decimal and hence 123 would display as 12C (C3 being the EBCDIC C character). For human-readable values, move each to a numeric edited variable (such as PIC S9(03) SIGN LEADING SEPARATE or PIC +++9) and display the numeric edited variable.

[Pragya]

Priya, you managed to mess up pretty much EVERYTHING you said. A COMP variable may be 2 bytes or 4 bytes or 8 bytes depending upon the PICTURE. The sign, if used (COMP variables can be unsigned), is the first bit of the value.And COMP has sign over punched at it last nibbleNo, you have described Zoned Decimal signs -- NOT COMP! And as pointed out a COMP-3 variable length depends upon the PICTURE digits.

123 as a 2-byte COMP variable will be X'007B'. 123 as PIC S9(03) COMP-3 variable will be X'123C'. 123 as a 3-byte signed zoned decimal variable will be X'F1F2C3'. All of this is CLEARLY explained in the Enterprise COBOL Language Reference manual.

Also, you can use DISPLAY -- but signed values may require interpretation since the values will be converted to zoned decimal and hence 123 would display as 12C (C3 being the EBCDIC C character). For human-readable values, move each to a numeric edited variable (such as PIC S9(03) SIGN LEADING SEPARATE or PIC +++9) and display the numeric edited variable.

Thanks.

Can we not display them without really moving to some other type variable and still make it human readable?

[enrico-sorichetti]

Can we not display them without really moving to some other type variable and still make it human readable?

did You care to try to understand the answer You were given ?

[Robert Sample]

Can we not display them without really moving to some other type variable and still make it human readable?

Yes -- as long as the human understands 12C is a +123 and 12L is -123 on the DISPLAY. If this is not acceptable, you MUST move the data to a different variable to DISPLAY it.

[Pragya]

Thanks Robert.