Inputting random numbers into an array

Question

I tried to create an array and fill it with random numbers using rand(), and it would seem that I got the code to work but when I return the data to the screen it all appears to be correct except in value arrayPrimary[5][2]. It just shows a garbage value and I cant seem to figure out why it would do that in only this spot. I'm still new to learning the C language so please be as descriptive as possible to help me understand:

#include <stdlib.h>

main ()
{
srand (time(NULL));
int arrayPrimary[5][5];
int x,y,a,b;

for(x=1; x<6; x++)
{

    for (y=1; y<6; y++)
    {

    int *z= &arrayPrimary[x][y];
    *z=rand() %10;  

    }
}

for(a=1; a<6; a++)
{
    for(b=1; b<6;b++)
    {
    printf ("The current value of [%d][%d] is:%d\n",a,b,arrayPrimary[a][b]);
    }

}
return 0;
}

Valid array indexes will be from 0 to 4 for both dimensions of arrayPrimary so you are invoking undefined behavior by accessing index 5. — Shafik Yaghmour
– Shafik Yaghmour, Commented Dec 28, 2013 at 19:05
I have both headers in my code I just forgot to copy them over. — Endon55
– Endon55, Commented Dec 28, 2013 at 19:09
Why are you bending yourself into a pretzel setting the values? What's wrong with arrayPrimary[x][y] = rand() % 10? — pjs
– pjs, Commented Dec 28, 2013 at 19:17

haccks · Accepted Answer · 2013-12-28 19:06:23Z

2

In C, array indexing starts from 0.
Change

for(a=1; a<6; a++)
{
    for(b=1; b<6;b++)

to

for(a=0; a<5; a++)
{
     for(b=0; b<5;b++)

answered Dec 28, 2013 at 19:06

haccks

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