Swap

#include <stdio.h>
#define SIZE 4
//deitel 3.46 page 136
void print_arr(int *,int);
void code_arr(int *,int);
void swap_arr(int *,int);
void decode_arr(int *,int);
void sw_elem(int *,int,int);

int main()
{
    int arr[SIZE];
    //scanf("%d %d %d %d",&arr[0],&arr[1],&arr[2],&arr[3]);correct, looks bad IMHO
    scanf("%d %d %d %d",arr,arr+1,arr+2,arr+3);//&arr[1] equals arr+1!!!

    print_arr(arr,SIZE);
    code_arr(arr,SIZE);
    print_arr(arr,SIZE);
    swap_arr(arr,SIZE);
    print_arr(arr,SIZE);
    swap_arr(arr,SIZE);
    print_arr(arr,SIZE);
    decode_arr(arr,SIZE);
    print_arr(arr,SIZE);



   return 0;
}
void print_arr(int *a,int s)
{
    int i;
    for(i=0;i<s;i++)
    {
        printf("%d\t",a[i]);
    }
    printf("\n");
}

void code_arr(int *a,int s)
{
    int i;
    for(i=0;i<s;i++)
    {
        a[i]=(a[i]+7)%10;
    }
}
void swap_arr(int *a,int s)
{
    sw_elem(a,0,2);//swaps elements with indexes 0 and 2
    sw_elem(a,1,3);//swaps elements with indexes 1 and 3
}
void decode_arr(int *a,int s)
{
    int i;
    for(i=0;i<s;i++)
    {
        a[i] = (a[i]>=8)? (a[i]-7):(a[i]+3);
    }
}
void sw_elem(int *a,int k, int l)
{
    int temp = a[k];
    a[k] = a[l];
    a[l] = temp;
}