C-Checking if input (float) is purely integer or float - c

Question

I want to check if the user input is purely integer or a float. I attempted to do this by using floor and ceilfand comparing the values to the original x value in a function. However, this seems to be a tad bit problematic as the function keeps returning 0 instead of 1 for certain numbers like 5.5, when floor(5.5)!=5.5 and ceilf(5.5)!=5.5. This is my code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>
#include <stdbool.h>
int intchecker(float x)//in a separate file
{
if (floor(x)==x && ceilf(x)==x)
{
//printf("%f",floor(x));
return 0;
}
else {
return 1;
}
}
int main()
{
char line[] = " +----+----+----+----+----+----+----+----+----+----+---+";
char numbers[] = " 0 5 10 15 20 25 30 35 40 45 50";
float balls,slots;
int slot[9];
printf("==========================================================\nGalton Box Simulation Machine\n==========================================================\n");
printf("Enter the number of balls [5-100]: ");
scanf("%f",& balls);
if (balls>100 || balls<5){
printf("/nInput is not within the range. Please try again.");
}
else if (intchecker(balls)==1){
printf("/nInput is not an integer. Please try again.");
}
else {
printf(" This is an integer.");
//some more code here
}
}
I tried placing just the intchecker code in another project, which seems to work fine without any bugs, unlike in the previous project, where when I used a printf statement to check if the floor(x) value was correct, it kept showing different answers, e.g. "-2.000000" when input was 5.2. This is my code for the second project:
#include <stdio.h>
#include <stdlib.h>
#include<math.h>
int main()
{
float x;
scanf("%f",&x);
if (floor(x)==x && ceilf(x)==x){
printf("Integer");
return 0;
}
else {
printf("Non-Integer");
return 1;
}
}
How is it possible that the second code works perfectly when the first code does not? Is something wrong with my way of writing/calling the function?(I am relatively new to functions-only 2 weeks of exposure so far)
I searched online and have seen many answers to check if input is integer or float, even on stackoverflow.com itself, but my wish is not to find out other ways to check if input is integer or float (for if I wished to do that, I could just google it, and there are many such questions on stackoverflow.com as well), but to comprehend why my first code does not work, for, as far as I know, it ought to work well without any of the bugs it is currently facing.
Any help is greatly appreciated!:)

Answer 1

Assuming a missing function declaration:
main.c is missing the prototype for int intchecker(float x) so main.c assumes the old-school prototype of int intchecker(int x) and the code exhibits undefined behavior. Anything could happen.
Add prototype in main.c or put it in separate.h and include that header file here and in separate.c
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <conio.h>
#include <stdbool.h>
int intchecker(float x);
int main(void) {
...