Runnable form of Duff's Device, written for clarity.

DuffsDevice.c

#include <stdio.h> 
 
void send (int count) 
{ 
    int n = (count+7) / 8; 
 
    switch (count % 8) { 
        do { 
            case 0: printf("%d.8\n", n); 
            case 7: printf("%d.7\n", n); 
            case 6: printf("%d.6\n", n); 
            case 5: printf("%d.5\n", n); 
            case 4: printf("%d.4\n", n); 
            case 3: printf("%d.3\n", n); 
            case 2: printf("%d.2\n", n); 
            case 1: printf("%d.1\n", n); 
        } while (--n > 0); 
    } 
} 
 
int main (int arc, char *argv[]) 
{ 
    send (atoi(argv[1])); 
}