How to pass an array to function and display the array's contents?-CodePudding

I was trying to a simple program of passing the inputted numbers of the arrays and displaying it using the function but it shows random value. What am I doing wrong?

#include<stdio.h>
#define size 5

void display();
int main()
{
    int arr[size];
    int i;

    for(i = 0; i < size; i  ){
        printf("Input a number at index %d: ", i);
        scanf("%d", &arr[i]);
        
    }
    display();
}

void display(){
    int i;
    int arr[size];
     for(i = 0; i < 5; i  )
        printf("Element[%d] = %d\n", i, arr[i]);
}

CodePudding user response：

You have two arrays with the same name but different scope. A variable declared in a function is not visible outside of an function. In your case the one stores the numbers and the one gets printed but they are not the same. Moving int arr[size]; to global scope would resolve this problem related to scope.

#include<stdio.h>
#define size 5

int arr[size];

void display(){
     for(int i = 0; i < 5; i  )
        printf("Element[%d] = %d\n", i, arr[i]);
}
int main()
{
    for(int i = 0; i < size; i  ){
        printf("Input a number at index %d: ", i);
        scanf("%d", &arr[i]);
    }
    display();
}

A better solution would be to avoid global variables and use a pointer to pass your array to the display function.

#include<stdio.h>
#define size 5

void display(int *arr){
     for(int i = 0; i < size ; i  )
        printf("Element[%d] = %d\n", i, arr[i]);
}
int main()
{
    int arr[size];
    for(int i = 0; i < size; i  ){
        printf("Input a number at index %d: ", i);
        scanf("%d", &arr[i]);
    }
    display(arr);
}

CodePudding user response：

You can't pass an array, but you can pass a pointer into it instead.

void print_elements(int *array, int length) {
    for (int i = 0; i < length; i  ) {
        printf("%d", array[i]);
    }
}

int foo[size];
print_elements(foo, size);

CodePudding user response：

You did not pass the array as an argument to the function, functions can only access variables passed as arguments or global variables. i changed your code a bit and added some checks for invalid values, now it should work.

#include<stdio.h>
#define SIZE 5

void display(int*, int);
int main()
{
    int arr[SIZE];
    int i;

    for(i = 0; i < SIZE; i  ){
        printf("Input a number at index %d: ", i);
        int res = scanf("%d", &arr[i]);
        if (res != 1) {
            printf("Not a valid integer scanned!");
            return -1;
        }
        
    }
    display(arr, SIZE);
   
  
}
void display(int* arr, int size){
    if (arr == NULL) {
        printf("Error! Null array!");
        return;
    }

     for(int i = 0; i < size; i  )
        printf("Element[%d] = %d\n", i, arr[i]);
}