Thread: array value overwriting another

Code:

#include <stdio.h>

int main(){

        int array111[5];
    
        printf("Please enter the 6 array111 numbers.\n");
        scanf("%d %d %d %d %d %d", &array111[0], &array111[1], &array111[2], &array111[3], &array111[4], &array111[5]);
        
    
        
    
        
        
     //set up the values for arr999
    int arr999[6];
    arr999[0] = 0;
    arr999[1] = 0;
    arr999[2] = 0;
    arr999[3] = 10;
    arr999[4] = 100;
    arr999[5] = 10000;
    arr999[6] = 1000000;
    
    printf("array111[0]== %d\n array111[1]== %d\n array111[2]== %d\n array111[3]== %d\n array111[4]== %d\n array111[5]== %d \n", array111[0], array111[1], array111[2], array111[3], array111[4], array111[5]);

}

Can anyone tell how array111[0] is being overwritten by anything I hardcode into arr999[6]? I can't figure it out

The issue is mainly that the arrays are too small for the number of values that you want to hold. The number of elements that any array can have ranges from 0 to N - 1 inclusive, where N is the number of elements. What is actually happening is that array111[6] overflows into array999[0] instead of breaking spectacularly. Since array999[0] happens to be located where array111[6] would be, it worked out for you, but you shouldn't depend on this behavior all the time. It's undefined.

Originally Posted by whiteflags

The issue is mainly that the arrays are too small for the number of values that you want to hold. The number of elements that any array can have ranges from 0 to N - 1 inclusive, where N is the number of elements. What is actually happening is that array111[6] overflows into array999[0] instead of breaking spectacularly. Since array999[0] happens to be located where array111[6] would be, it worked out for you, but you shouldn't depend on this behavior all the time. It's undefined.

Thank you, I misunderstood some important things about arrays. This was fixed by increasing the capacity of each array by 1.