C program to return multiple values from a function

  • Write a program in C to return multiple values form a function using array, pointers and structures.
  • How to return more than one value form a function in C programming language.

Required knowledge : Structures in C, Pointers in C
Here is the syntax of function declaration in C:
return_type function_name(type arg1, type arg2 .....);
A function can only return one value to it's calling function as per function syntax. However a function can any of the following values:
  • Basic data types: int, float, char, double stc.
  • Pointer : Pointer to a basic data type variable(like integer pointer), base address of an array, pointer to a structure.
  • Structure : A structure variable.

Returning multiple values from a function using array

If we want to return multiple values of same data type then we should return the base pointer of an array of that data type. 
#include<stdio.h>


int* getNEvenNumbers(int N, int *array){
    int i;
 
    for(i = 0; i < N; i++){
        array[i] = 2*(i+1);
    }
 
    return array;
}

int main(){
    int i, N, array[100];
    
    printf("Enter one integers\n");
    scanf("%d", &N);
    
    getNEvenNumbers(N, array);
    
    printf("%d Even Numbers\n", N);
    for(i = 0; i < N; i++)
        printf("%d ", array[i]);
 
    return 0;
}
Output 
Enter one integers
8
8 Even Numbers
2 4 6 8 10 12 14 16

Returning multiple values from a function by passing variable address as parameter

We can pass multiple addresses of variables as input parameters to a function. Inside function body, we can store the return values at the passed memory locations. 
#include<stdio.h>

int getSumAndProduct(int a, int b, int *product){
    *product = a * b;
    return a + b;
}

int main(){
    int a, b, sum, product;
    
    printf("Enter two integers\n");
    scanf("%d %d", &a, &b);
    
    sum = getSumAndProduct(a, b, &product);
    
    printf("Sum = %d\nProduct = %d", sum, product);
 
    return 0;
}
Output 
Enter two integers
3 8
Sum = 11
Product = 24

Returning a structure variable from a function.

Structure is a user defined data type that groups different data types into a single unit. If we want to return values of different data types, then we can encapsulate all return values in a structure variable and return it from a function. 
#include<stdio.h>

struct data {
    int sum, product;
};

typedef struct data myStruct;

myStruct getSumAndProduct(int a, int b){
    myStruct s;
    s.sum = a + b;
    s.product = a * b;
    return s;
}

int main(){
    int a, b;
    myStruct result;
    
    printf("Enter two integers\n");
    scanf("%d %d", &a, &b);
    
    result = getSumAndProduct(a, b);
    
    printf("Sum = %d\nProduct = %d", result.sum, result.product);
 
    return 0;
}
Output 
Enter two integers
3 7
Sum = 10
Product = 21
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