Code:
#include <stdio.h>
#include <string.h>
#include <ctype.h>
void atbash(char *in, char *out);
int main(void)
{
char out[100];
atbash("abcdefghijklmnopqrstuvwxyz", out);//You're passing this by value, hence you'll never see output on screen
printf("%s", out);
getchar();
return 0;
}
void atbash(char *in, char *out)
{
int len = strlen(in); /*en holds length of encrypt*/
for (len--; len >= 0; len--){
*out = in[len];
out++; Also i removed the * as that is a reference to the value not the memory address which is what you want to be incrementing
}
*out = '\0'; /*ULL terminiate*/
}