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  1. #include <stdio.h>
  2.  
  3. int bit[] = { 1<<0, 1<<1, 1<<2, 1<<3 };
  4.  
  5. struct fullAdderReturn
  6. {
  7.     int sum;
  8.     int carryOut;
  9. };
  10.  
  11. typedef struct fullAdderReturn FAR_t;
  12.  
  13. FAR_t oneBitAdder(int a, int b, int carryIn)
  14. {
  15.     FAR_t output;
  16.     output.sum = a^b^carryIn;
  17.     output.carryOut = (a&b) | (a&carryIn) | (a&carryIn);
  18.  
  19.     return output;
  20. }
  21.  
  22. FAR_t twoBitAdder(int a, int b, int carryIn)
  23. {
  24.     FAR_t output, temp;
  25.     output.sum = 0;
  26.  
  27.     //add the least significant bits
  28.     temp = oneBitAdder(a&bit[0], b&bit[0], carryIn);
  29.  
  30.     //set the sum
  31.     output.sum  |= temp.sum << 0;
  32.  
  33.     //add the next bits using carry from last add
  34.     temp = oneBitAdder(a&bit[1], b&bit[1], temp.carryOut);
  35.  
  36.     //shift up the output and or it together with result of last add
  37.     output.sum |= ((temp.sum) << 1);
  38.     output.carryOut = temp.carryOut;
  39.  
  40.     return output;
  41. }
  42.  
  43. int main( void )
  44. {
  45.     int a = 1;
  46.     int b = 1;
  47.  
  48.     int carryIn = 1;
  49.  
  50.  
  51.     FAR_t t = twoBitAdder(a, b, carryIn);
  52.  
  53.     printf("sum = %d, carryOut = %d\n", t.sum, t.carryOut);
  54.  
  55.     return 0;
  56. }
Success #stdin #stdout 0s 1832KB
comments (?)
stdin 
Standard input is empty
stdout 
sum = 3, carryOut = 0
https://ideone.com/NRoQMS
language:
C (gcc 8.3)
created:
12 years ago
visibility:
public

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