When I taught college level programming classes I had an assignment that I gave out every term to my C Programming students. I don't remember the wording of the assignment but it required all of the functions below to solve it - and this was the solution I would pass out after they had turned their assignments in for grading. It was written in Mix C but should be easily adapted to just about any compiler.
Enjoy!
Tom
#include <stdio>
int len;
unsigned max_value;
main()
{
unsigned uarg1;
int iarg1, iarg2;
printf("\nCalculating word length ...");
wordlength();
printf("\nWord length of this machine is %d bits\n",len);
printf("Maximum value which can be stored ");
printf("in one word is %u\n",max_value);
printf("\n\nRotating values ...");
uarg1 = 124;
iarg1 = 3;
rightrot(uarg1,iarg1);
uarg1 = 336;
iarg1 = 4;
rightrot(uarg1,iarg1);
uarg1 = 747;
iarg1 = 1;
rightrot(uarg1,iarg1);
printf("\n\n\nInverting bits ... ");
uarg1 = 1024;
iarg1 = 5;
iarg2 = 3;
invert(uarg1,iarg1,iarg2);
uarg1 = 577;
iarg1 = 7;
iarg2 = 5;
invert(uarg1,iarg1,iarg2);
uarg1 = 322;
iarg1 = 6;
iarg2 = 4;
invert(uarg1,iarg1,iarg2);
printf("\n\n\nNORMAL PROGRAM TERMINATION\n\n");
} /* end of main() */
/* ----------------------------------------------------------------- */
wordlength() /* calculates word length & max value */
{
unsigned int value;
int j;
value = ~0;
while (((value >>= 1) ^ 0) != 0)
++len;
++len;
max_value = 1;
for (j=(len-1); j>=0; --j)
max_value = max_value * 2;
max_value = max_value - 1;
return(len,max_value);
} /* end of wordlength() */
/* ----------------------------------------------------------------- */
rightrot(n,b)
unsigned n;
int b;
{
unsigned work;
int i, j;
printf("\n\nRotating %u right by %d bits\n",n,b);
binary(n);
for (i=1; i<=b; i++)
{
work = n & 1;
work <<= (len - 1);
n >>= 1;
n |= work;
}
printf("\nResult: %u\n",n);
binary(n);
return(0);
} /* end of rightrot() */
/* ---------------------------------------------------------------- */
binary(v) /* displays v as a binary number */
unsigned v;
{
unsigned mask;
int i;
char stak[128];
mask = 001;
for (i=0; i<len; i++)
{
stak[i] = '0';
if ((v & mask) == 1) stak[i] = '1';
v >>= 1;
}
printf("Binary representation is: ");
for (i=len-1; i>=0; --i)
putchar(stak[i]);
return(0);
} /* end of binary() */
/* ---------------------------------------------------------------- */
invert(x,p,n) /* inverts n bits of x beginnint at p */
unsigned x;
int n,p;
{
unsigned work;
int i,j,nr;
printf("\n\nBeginning value = %u\n",x);
binary(x);
printf("\nInverting %d bits starting at %d\n",n,p);
for (i=0; i<p; i++)
{
work = x & 1;
work <<= (len - 1);
x >>= 1;
x |= work;
}
for (i = 1; i<=n; i++)
{
j = x & 1;
if (j == 0) j = 1;
else j = 0;
j <<= (len - 1);
x >>= 1;
x |= j;
}
for (i=1; i<=len-(n+p); i++)
{
work = x & 1;
work <<= (len-1);
x >>= 1;
x |= work;
}
printf("The new value is %u\n",x);
binary(x);
return(0);
} /* end of invert() */
