Thread: C programming arrays

What is printed by the following code?

Code:

int s[4] = {9,1,2,5};
printf("%d\n", s[4]);

When I run this program I get 0, however I'm not sure why it is that it prints 0. Could anyone explain this to me?

You declare s to be an array with 4 items. In C, arrays start at 0, so valid indexes are s[0]...s[3]. s[4] does not print the whole array (you need to do that one element at a time). Instead, it tries to print the 5th element of an array with only 4 elements. This is an out of bounds error, and results in undefined behavior, meaning anything can happen though likely it will vary from "random" behavior (like printing a 0) to program crashes due to invalid memory accesses.

I suggest you re-read carefully the section on arrays in your textbook or whatever online tutorials you're using.

Thanks, I read through the section again and got a little bit better of handle on it.
However now I am working on this.

Code:

#include <stdio.h>
int main(){
    int x[7] ={4,2,1,6,3,8,9};
    int min = x[0];
    int i;
    for (i = 0; i < 7; ++i) {
       if (x[i] < min) {
       min = x[i];
       }
    }
    printf("%d\n", min);
}

I want this program to print the position of the smallest value rather than the smallest value itself. Therefore instead of printing 1 it should be printing 2 because that is the position of the smallest value.
Any help?

If 'x[i]' represents a value, then 'i' represents the position of that value in the array. You're using the variable "min" to keep track of the smallest value - so why not make another variable to keep track of which position the minimum value is found?

Right, just like others said...add additional variable such as int minpos and within your "if" statement just add under min = x[i]; minpos = i ; and print minpos, that will give you the location within the array for the lowest number.

Two notes. First, regarding your question, it might be a bit easier if you gave better variable names (they're not bad as is, but could be better) to what you wanted to keep track of:

Code:

int min_value = x[0];
int min_index = ???

Second, even for a trivial program like this, you should use a constant for your array size, and used it in the declaration, any loops, etc:

Code:

#define ARRAY_SIZE 7
...
int x[ARRAY_SIZE] = {...};
for (i = 0; i < ARRAY_SIZE; i++)

That would make changing your array size (e.g. from 4 to 7) much easier, you only have to change the #define, and in this case the initial values. This will become absolutely critical for writing, testing and maintaining your programs as they become more complex.