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Displaying binary numbers

 
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Displaying binary numbers
PostPosted: Thu Feb 19, 2009 1:17 pm     Reply with quote
I want to work in binary for some aspects of my programming but I can't find anything on binary for C. Such as in a PRINTF statement I want to display a variable as a binary number. From what I have found you can only display as a decimal, hex or octal numbers. Anyone have any ideas??

Thanks
treitmey



Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA

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PostPosted: Thu Feb 19, 2009 1:38 pm     Reply with quote
Code:
//=== display_binary ===//
void display_binary(char c){
  int8 i=7;
  putc('0');
  putc('b');
  do
  {
    if( c & 0x80 ) putc('1');
    else putc('0');
    c <<= 1;
  } while(i--);
}
aaaaamartin



Joined: 17 Apr 2005
Posts: 39
Location: Germany Stuttgart

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PostPosted: Thu Feb 19, 2009 1:45 pm     Reply with quote
This is done using the binary operators & | ^ .
Basically you need to check each bit of your variable.

You can also use bitwise shifting << >> in a loop to test all bits one by one.

Here's an example, for keeping it simple a non-recursive approach.


Code:

int x;
int foo = 170;
//  Testing the lefmost 8 Bits and print them.
for(x=7; x>=0; x--) {
   if( foo & (1 << x) > 0) {
      putc('1');
   } else {
      putc('0');
   }
}
ckielstra



Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands

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PostPosted: Thu Feb 19, 2009 3:40 pm     Reply with quote
Code:
for(x=7; x>=0; x--) {
Be careful, in CCS the integers are unsigned by default. After 0 the value of x wraps to 255 which is >= 0 and the loop will never end.
Change to:
Code:
for(x=8; x>0; x--) {
Or change x to be a signed integer.
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