Please note - THIS IS UNTESTED - but syntactically valid <grin>

It may not be quite right but you should be able to see the basic principal in action. You start by dividing by a factor of 2 to shift the bit you want to the least significant position. Division by 2 then pushes that value into the remainder.

computes could probably be used to simplify the process some but I wanted you to see the mechanics of what was happening.

The alternative is to use the same approach but to repetitively divide by 2 to push the bits one by one into the remainder and then store the bit values in an array.

Identification Division. Program-Id. BITSET.
Data Division.
Working-Storage Section.
01 x.
05 bin-value pic 9(4) comp-4 value zero.
05 filler redefines bin-value.
10 filler pic x.
10 char-value pic x.

77 bit-number pic 9.
77 actual-bit pic 9.
77 top-bits pic 9(4).
77 shift-value pic 9(4).
77 left-bits pic 9(4).
77 right-bits pic 9(4).

* this contains the byte that is bit sensitive
77 char-bits pic x.

Procedure Division.
Bit-Play.
move char-bits to char-value.

* Isolate a specific bit
If bit-number < 8
compute shift-value = 2 ** (8 - bit-number)
divide bin-value by shift-value
giving left-bits
remainder right-bits
End-If.
divide left-bits by 2
giving left-bits
remainder actual-bit.

* To set the bit
move 1 to actual-bit.
multiply left-bits by 2 giving bin-value.
add actual-bit to bin-value.

If bit-number < 8
multiply bin-value by shift-value
add right-bits to bin-value
End-If.

Hope this helps - sorry I haven't got time to be sure it works.


Jon Paris

www.Partner400.com
www.SystemiDeveloper.com



On Jan 12, 2011, at 3:32 PM, Jason Abreu wrote:

I realize that the PIC 1 clause is for display usage only. It was just
the first thing that had come to mind.

I can get this:

01 WORK.
05 CHAR PIC X(01) VALUE X'00'.
05 BIN REDEFINES CHAR
PIC 9(01) COMP-3.

But the question is still how to do bit manipulation to set a specific
bit to "on" or "off."

I do not know any RPG and, due to in-house coding standards, am looking
for a COBOL solution. Ideally, I would be able to redefine a binary
data type into bits and use 88-level items to turn them on or off.

Thanks,

Jason Abreu
Abreu Innovations, Inc.
jason.abreu@xxxxxxxxxxxxxxxxxxxx
http://www.abreuinnovations.com/

On 1/12/2011 3:19 PM, Jon Paris wrote:
Well Pic 1 means a single byte indicator so that won't help.

It is years since I did this but in the pre-ILE days I did it with a simple divide/multiply routine. Don't have a sample of the code handy but it is not hard to do. Depending on what you want, you can either divide by the appropriate power of 2 to shift the bit in question to the least significant position, then divide by 2 to isolate the bit in question (in the remainder) change that value as you wish and reverse the process.

If you want to test/set any arbitrary bit then it is easier to just use a divide by 2 loop and store the remainders in an array. Test/change as desired and rebuild by a repetitive multiply loop.

These days I would code it in RPGIV and use the bit oriented functions in RPG IV to do the work. Then call the RPGIV routine form the COBOL code - probably much easier.


Jon Paris

www.Partner400.com
www.SystemiDeveloper.com



On Jan 12, 2011, at 2:59 PM, Jason Abreu wrote:

Does anybody have experience with bit manipulation in COBOL?

I would like to be able to switch individual bits on/off in a single byte.

I imagined something like:

01 WORK.
05 CHAR-BYTE PIC X(01) VALUE X'40'.
05 BINARY-REP REDEFINES CHAR-BYTE.
10 BIT-1 PIC 1.
88 BIT-1-ON VALUE B'1'.
88 BIT-1-OFF VALUE B'1'.
... repeat for all 8 bits.


So usage could be something like

SET BIT-1-ON TO TRUE.
MOVE CHAR-BYTE TO FILE-FIELD.

Any ideas on this?
Thanks, ahead of time!
--
Jason Abreu
Abreu Innovations, Inc.
jason.abreu@xxxxxxxxxxxxxxxxxxxx
http://www.abreuinnovations.com/
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