Heksadecimalna tablica mnozenja

#include <stdio.h>
#include <string.h>
void heksa_tablica_mnozenja(void){
    int i,j;
    for (i=1;i<=15;i++){
        for (j=1;j<=15;j++)
            printf("%3x ",i*j);
        printf("\n\n");
    }
}
void heksa_tablica_sabiranja(void){
    int i,j;
    for (i=0;i<=15;i++){
        for (j=0;j<=15;j++)
            printf("%3x ",i+j);
        printf("\n\n");
    }
}
void okta_tablica_sabiranja(void){
    int i,j;
    for (i=0;i<=7;i++){
        for (j=0;j<=7;j++)
            printf("%3o ",i+j);
        printf("\n\n");
    }
}
void okta_tablica_mnozenja(void){
    int i,j;
    for (i=1;i<=7;i++){
        for (j=1;j<=7;j++)
            printf("%3o ",i*j);
        printf("\n\n");
    }
}
void binarni(void){
    int a=0,stepen=128,suma=0;
    int i;
    for (i=7;i>0;i--){
        printf("%3d ",stepen);
        stepen/=2;
    }
    printf("%3d\n",stepen);
    stepen=128;
    for (i=7;i>0;i--){
        suma+=stepen;
        printf("%d ",suma);
        stepen/=2;
    }
    printf("%d\n",suma+stepen);
}
void main(int argc, char *argv[]){
    heksa_tablica_sabiranja();
    heksa_tablica_mnozenja();
    binarni();
    okta_tablica_mnozenja();
    okta_tablica_sabiranja();
}