3-inv by two inverters
You have plenty of ANDs and ORs, but only 2 inverters. Can you invert more than 2 independent inputs?
•CHALLENGE: Come up with a combinational circuit using ANDs, ORs, and at most 2 inverters that inverts A, B, and C !
•Such a circuit exists. What does that mean?
-If we can invert 3 signals using 2 inverters, can we use 2 of the pseudo-inverters to invert 3 more signals?
-Do we need only 2 inverters to make ANY combinational circuit?

#include 
void main(){
 int a,b,c,x,y,z,g,h,a1,b1,c1,x1,y1,z1;
 int i;
 for(i=0;i<8;i++){ //a =" i" b =" (i">> 1;
  c = (i & 4) >> 2;

  x = a & b & c; // == three ones
  y = a & b | a & c | b & c; // == at least two ones
  z = a | b | c; // == at least single one

  //Here are our 2 inverters
  g = !(y); // zero or single one
  h = !(x | g & z); //zero or two ones
  
  x1 = g | h;  //zero or single, or two ones
  y1 = g; // zero or single one
  z1 = g & h; // zero one
  a1 = b & c & x1 | (b | c) & y1 | z1; //three zeros or ...
  b1 = a & c & x1 | (a | c) & y1 | z1;
  c1 = b & a & x1 | (b | a) & y1 | z1;

  //print outputs to verify
  printf("%d-->%d   %d-->%d   %d-->%d\n",a,a1,b,b1,c,c1);
  printf("x1=%d,y1=%d,z1=%d\n",x1,y1,z1);
 }
}

/*
Input output
a b c x1 y1 z1
0 0 0 1  1  1  
0 0 1 1  1  0
0 1 0 1  1  0
1 0 0 1  1  0
1 0 1 1  0  0
0 1 1 1  0  0
1 1 0 1  0  0
1 1 1 0  0  0
*/

- posted by Pop @ 3:10 PM