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srikanth.bh · Beginner Joined: 23 Jul 2004 Posts: 8 Topics: 4

Hi all,
I am trying to move a variable of pic 9(10) to s9(9) comp. getting some junk values in output however i try. please suggest how to accomplish this.

thanks,
kanth

kolusu · Posted: Wed Aug 11, 2004 3:16 pm Post subject:

Srikanth,

You need to tell us what you meant by junk value. The following program shows the move of 9(10) to s9(09) comp.

srikanth.bh · Beginner Joined: 23 Jul 2004 Posts: 8 Topics: 4

Kolusu, thanks for the response. Initially when i tried this direct move i got strange output.

01 A PIC 9(10) VALUE 3420009659
01 B PIC S9(9) COMP.

MOVE A TO B.

OUTPUT:
A = 3420009659
B = -874957637

i'm failing to understand how B had such a value.

srikanth.bh · Beginner Joined: 23 Jul 2004 Posts: 8 Topics: 4

Actually, the MOVE statement in inside a loop. so i think each time the move is made the values are getting computed with the old value in comp. when i tried initializing the comp filed before each move i could get the result correctly.

sorry for taking your time, thanks.

Mike Chantrey · Posted: Thu Aug 12, 2004 10:25 am Post subject:

The maximum positive value you can store in an S9(9) COMP field is 2^31 which is 2147483648, i.e. the value you are trying to move is too big. So it wraps around into the negative range. Negative values are stored in 'twos complement' fashion so if you convert the value in B to its unsigned equivalent you will see that the unsigned value is actually correct, i.e. 2^32 - 874957637 = 3420009659

As far as I can see this explains you result rather than your loops...

srikanth.bh · Beginner Joined: 23 Jul 2004 Posts: 8 Topics: 4

that makes more sense mike. thanks for clarifying.