Custom average function with array input does not return value in C

Question

I made a program which accepts input for 30 users (About their age) and then the array was supposed to be an input in a custom function made by me (avg_age) However the average printed on screen is 0.0000 (for 30 non-zero values) That is why I think it does not return anything.

#include <stdio.h>

float avg_age(int age[]);

main()

{
    int i=0,age[30]={0},intemp;

do{
    printf("Input age for 30 users: ");
    scanf("%d",&intemp);
    if(intemp>0 && intemp<100)
        intemp=age[i];
    else i--;
    i++;
}while(i<30 || intemp<0 || intemp>100);

printf("\nAverage age of 30 users: %f\n",avg_age(age));




float avg_age(int age[]){
    int i,avg=0;
    for(i=0;i<30;i++)
        avg+=age[i];
    avg=(float)avg/30;
    return avg;
    }

}

Answer 1

Take out the function definition of avg_age out of the main. You declared avg as int but it should be declared float to store float values.

float avg = 0.0;  

In main intemp=age[i]; is not storing the inputs to the array age instead assigning 0 each time to intemp. Change it to

age[i] = intemp;  

Your modified code: (for 5 users)

#include <stdio.h>
#define N 5

float avg_age(int age[]);

int main(void)
{
    int i=0,age[N]={0},intemp;

    do{
       printf("Input age for %d users: ", N);
       scanf("%d",&intemp);
       if(intemp>0 && intemp<100)
           age[i] = intemp;
       else i--;
       i++;
    }while(i<N || intemp<0 || intemp>100);

    printf("\nAverage age of %d users: %f\n",N, avg_age(age));
    return 0;
}

float avg_age(int age[]){
    int i;
    float avg=0.0;
    for(i=0;i<N;i++)
        avg+=age[i];
    avg=(float)avg/N;
    return avg;
 }  

Here is the tested code.

Answer 2

Your avg inside avg_age should be a float

float avg_age(int age[]){
  int i; float sum=0.0;
  for(i=0;i<30;i++)
     sum += age[i];
  return sum/30;
}

and of course the above function should be outside of main (preferably before it).

BTW, you should have compiled with all warnings and debugging info (e.g. with gcc -Wall -g). The compiler certainly would have warned you! Also, learn how to use the debugger (e.g. gdb)