Something

/*
 * franjo stipanovic
 * programiranje - dz 8 2
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int strdupchr(const char *src, char dch, char *dest);
int main()
{
   char input[100], dch, num, *output;
   scanf("%s %c", input, &dch);
   output = (char *) malloc(strlen(input) * sizeof(char) + 1);
   printf("INPUT: %s\t%c\n", input, dch);
   num = strdupchr(input, dch, output);
   printf("OUTPUT: %s\t%d\n", output, num);
   free(output);
   getche();
   return 0;
}

/*
 - look for 'dch' occurrences and copy the 'src' into 'dest' by doubling every occurrence
*/
int strdupchr(const char *src, char dch, char *dest)
{
   int num = 0;
   while (*src) {
      if (*src == dch) {
         *dest++ = *src;
         num++;
      }
      *dest++ = *src++;
   }
   return num;
}