Inputting integer values into an Array in C

This part of code

  int* z;
    *z==arrayPrimary[x][y];
    printf("please enter a value for [%d][%d]:",x,y);
    scanf("%d", &z);

Should read

    printf("please enter a value for [%d][%d]:",x,y);
    scanf("%d", &arrayPrimary[x][y]);

You should also consider checking the return value of scanf

There are several things wrong here.

First of all, you use == (comparison) where you meant to use = (assignment) (This is rather ironic, considering how often people the reverse of that mistake). This means that *z is never initialized. For that matter, z itself is never initialized, so you're accessing garbage memory.

Your error probably occurs when you try to write an integer ("%d") into a pointer (z). Remember, scanf takes a pointer to where you want the input to be written to, so if your input is an int, you'll want to pass an pointer to an int. You're passing a pointer to a pointer to an int.

The pointer logic here is probably what has you the most confused, so let's go through that in detail:

• arrayPrimary[x][y] is an integer that has an address in memory like any normal variable.
• scanf needs to know this location in order to write the value into your array.
• It looks like you're trying to use another variable, z, to serve as an argument to scanf. However, even if you copy the value of arrayPrimary[x][y] to the address z points to, z is still a different variable from your array.
• The memory address of z (&z) has no relation whatsoever to your array. When you pass &z to scanf, scanf will look at this address and write the input to it. Therefore, you are directing the input into z, not to your array.

Try this:

for (y=0; y<2; y++)
{
    int *z = &arrayPrimary[x][y];
    printf("please enter a value for [%d][%d]:",x,y);
    scanf("%d", z);

}

This way, it goes like this:

• You create a pointer, z, that points to the data you want to change (namelyarrayPrimary[x][y]).
• You pass this data yo scanf, which writes input to where z points to-- namely, arrayPrimary[x][y].

However, there's no need for a separate pointer. You can just write:

for (y=0; y<2; y++)
{
    printf("please enter a value for [%d][%d]:",x,y);
    scanf("%d", &arrayPrimary[x][y]);
}

If z already is a pointer to your desired memory location, there's no point in using &z in your scanf; just use z.

(EDIT: Assuming you get your = straightened out as pointed out in the comments.)

With your line:

int *z;

you just set up a pointer to an int. In your next line:

*z==arrayPrimary[x][y];

you first dereference that pointer (*z), so you say 'I now want to use the value, the pointer points to'. Next you compare that value with arrayPrimary[x][y] and the result of that comparison is discarded. Here you should get a warning by your compiler, something like 'statement has no effect' or so. So this line effectively does nothing. Try:

int *z = &arrayPrimary[x][y];

instead of the two lines I talked about the last few lines.

#include<stdio.h>
#include<iostream>
int main ()
{
    int arrayPrimary[2][2];
    for(int i=0; i<2; i++)
    {
        for (int j=0; j<2; j++)
        {
            printf("Please Enter value for %d%d",i,j);
            scanf("%d",&arrayPrimary[i][j]);
        }
    }
    for(int i=0; i<2; i++){
        for(int j=0; j<2;j++){
            printf("%d",arrayPrimary[i][j]);
            printf(" ");
        }
        printf("\n");
    }
    return 0;
}