I received this error for a binary search programme in C, despite the fact that it requested for inputs and produced the right output. The error message I received in the output window is shown below.

binarysearch.c: In function 'sort': binarysearch.c:22:5: warning:
  implicit declaration of function 'bin'
  [-Wimplicit-function-declaration]
       bin(a,size);//invokes bin(int,int) to find element
       ^~~ binarysearch.c: At top level: binarysearch.c:24:6: warning: conflicting types for 'bin'  void bin(int a[],int size)//finds element
  using binary sort technique and return its index
       ^~~ binarysearch.c:22:5: note: previous implicit declaration of 'bin' was here
       bin(a,size);//invokes bin(int,int) to find element
       ^~~
  Enter size of array

How can I fix the problem?
What does the error indicate?
Why did it continue to ask for inputs after an error occurred?

I created two functions. As mentioned in this documentation, the first function, void sort(int a[],int size), used selection sort to sort the array and printed it before invoking the second function, void bin(int a[],int size), which used binary search to find an element and printed its position(index+1). The main function was then written.

The programme is as follows:

#include<stdio.h>
void sort(int a[],int size)//sorts array in ascending order
{
    int min;
    for(int i=0;i<size;i++)
    {
        for(int j=0;j<size;j++)
        {
           if(a[j]>a[j+1])//checks if elements at position 'i' is greater than element at position (i+1) and exchanges values if true
           {
              min=a[j];
              a[j]=a[j+1];
              a[j+1]=min;
           }
        }
    }
    printf("Sorted array:");
    for(int i=0;i<size;i++)//prints sorted array
    {
        printf("%d  ",a[i]);
    }
    bin(a,size);//invokes bin(int,int) to find element
}
void bin(int a[],int size)//finds element using binary sort technique and return its index
{
    int key;//stores element to be found
    printf("\nEnter element to be found:");
    scanf("%d",&key);
    int sp=0;//stores starting point which is initially 0
    int ep=size-1;//stores ending point which is initially one less than size of array
    int mid;//stores average of sp and ep
    int count=0;//counter
    printf("Occurrence is:");
    while(sp<=ep)
    {
        mid=(sp+ep)/2;
        if(a[mid]>key)//to run loop for elements that are before mid
        {
            ep=mid-1;
        }
        else if(a[mid]<key)//to run loop for elements that are after mid 
        {
            sp=mid+1;
        }
        else if(a[mid]==key)//when element is found
        {
            printf("%d",mid+1);
            count+=1;
            break;//to stop the loop
        }
    }
    if(count==0)//in case element is not found
    printf("ELEMENT NOT FOUND");
}
    int main()
    {
        int n;//stores size of array
        printf("Enter size of array:");
        scanf("%d",&n);
        int arr[n];//creates array of size n
        printf("Enter elements:");
        for(int i=0;i<n;i++)
        {
            scanf("%d",&arr[i]);
        }
        sort(arr,n);//invoke sort(int,int) function which later invokes bin(int,int) function
        return 0;
    }