Input values into array using function

This is a discussion on Input values into array using function within the C Programming forums, part of the General Programming Boards category; Original Instructions: "Write a C function that will input values into an array of type int. Have the array and ...

  1. #1
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    Question Input values into array using function

    Original Instructions: "Write a C function that will input values into an array of type int. Have the array and the number of elements in the array passed as parameters to your function. Use a local pointer variable to traverse the array. "

    So this is what I've come up with, was wondering if someone could have a look at it because I wasn't quite clear on the instructions exactly. Maybe if you've dealt with this sort of problem before you can tell me if I'm on the right track, the second part of the problem will be to then write a function that outputs the contents of the array using a function.

    Code:
    /*
    
    My name is Jack Trocinski
    
    */
    
    #include <stdio.h>
    #include <stdlib.h>
    
    void input(int *ptr, int j);
    
    int main()
    {
    	int j; // number of elements in array
    	int *ptr; // memory allocation
    	
    	printf("Please enter the amount of elements you wish to have in the array: ");
    	scanf("%d", &j);
    	
    	if (j > 0) {
    		input (ptr, j);
    	}
    	
    	else printf("Sorry, you have entered an invalid number.\n");
    	
    	system("pause");
    	return 0;
    }
    
    void input(int *ptr, int j) {
    
    int i; // used in for loop
    
    ptr = malloc( j * sizeof(*ptr) );
    		for ( i = 0; i < j; ++i) {
    			printf("Input a value to the array and press enter: ");
    			scanf("%d", &ptr[i]);
    			}
    }
    Everything compiles nicely, my problem is strictly did I get the right concept writing this type of code.

  2. #2
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    Looks alright. Except that the array is not accessible once you leave the input() function. Say you want to continue processing by calling another function after that. The input() function did not communicate the malloc'ed address back. Otherwise the code does exactly what was asked.

  3. #3
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    I see so it needs to return a value. Ok, I'll will play around with this.

  4. #4
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    Either return the value, or make the passed parameter such that the function can pass it back through there, i.e. address-of. This may be more advanced than what you've learned... maybe not.

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