How do I make this C program to accept a negative input

[mexabet]

I'm creating a basic C program that I want to accept both positive and negative inputs. However, as it is it doesn't accept negative inputs. Any help on how to fix it will be much appreciated. here is the code:

int main(void){

    // Here we declare integer and floating point number and assign values to them
    int change = 0;
    float fchange = 0.00;

    // Let's ask the user how much is owed and get his/her input
    printf("How much change do I owe you? ");
    fchange = GetFloat();

    // Let's multiply the Dollar value by 100
    change = (int)roundf(fchange*100.0);

    // Here we assign values to coin denominations
    int quarters = change/25;
    change = change % 25;

    int dimes = change/10;
    change = change % 10;

    int nickels = change/5;
    change = change % 5;

[L7Sqr]

Without the implementation of GetFloat the best I can offer is to change GetFloat to accept negative input.

Perhaps if you provide the definition of that function we could help you a bit more.

[mexabet]

Thanks for your response.
The program include custom library file that defines the GetFloat function, and this is what it does:

/*
 * Reads a line of text from standard input and returns the equivalent
 * float as precisely as possible; if text does not represent a float,
 * user is prompted to retry.  Leading and trailing whitespace is ignored.
 * For simplicity, overflow and underflow are not detected.  If line can't
 * be read, returns FLT_MAX.
 */

float 
GetFloat(void);

I really don't want to change GetFloat, for some reasons.

[Ancient Dragon]

Did you write GetFloat()? Post it's source code so that we don't have to guess what it does.

[mexabet]

Thanks for replying. As follows is the source code of the header file that defines GetFloat:

#ifndef _CS50_H
#define _CS50_H

#include <float.h>
#include <limits.h>
#include <stdbool.h>
#include <stdlib.h>


/*
 * Our own data type for string variables.
 */

typedef char *string;


/*
 * Reads a line of text from standard input and returns the equivalent
 * char; if text does not represent a char, user is prompted to retry.
 * Leading and trailing whitespace is ignored.  If line can't be read,
 * returns CHAR_MAX.
 */

char 
GetChar(void);


/*
 * Reads a line of text from standard input and returns the equivalent
 * double as precisely as possible; if text does not represent a
 * double, user is prompted to retry.  Leading and trailing whitespace
 * is ignored.  For simplicity, overflow and underflow are not detected.
 * If line can't be read, returns DBL_MAX.
 */

double 
GetDouble(void);


/*
 * Reads a line of text from standard input and returns the equivalent
 * float as precisely as possible; if text does not represent a float,
 * user is prompted to retry.  Leading and trailing whitespace is ignored.
 * For simplicity, overflow and underflow are not detected.  If line can't
 * be read, returns FLT_MAX.
 */

float 
GetFloat(void);


/*
 * Reads a line of text from standard input and returns it as an
 * int in the range of [-2^31 + 1, 2^31 - 2], if possible; if text
 * does not represent such an int, user is prompted to retry.  Leading
 * and trailing whitespace is ignored.  For simplicity, overflow is not
 * detected.  If line can't be read, returns INT_MAX.
 */

int 
GetInt(void);


/*
 * Reads a line of text from standard input and returns an equivalent
 * long long in the range [-2^63 + 1, 2^63 - 2], if possible; if text
 * does not represent such a long long, user is prompted to retry.
 * Leading and trailing whitespace is ignored.  For simplicity, overflow
 * is not detected.  If line can't be read, returns LLONG_MAX.
 */

long long 
GetLongLong(void);


/*
 * Reads a line of text from standard input and returns it as a
 * string (char *), sans trailing newline character.  (Ergo, if
 * user inputs only "\n", returns "" not NULL.)  Returns NULL
 * upon error or no input whatsoever (i.e., just EOF).  Leading
 * and trailing whitespace is not ignored.  Stores string on heap
 * (via malloc); memory must be freed by caller to avoid leak.
 */

string GetString(void);



#endif

[mexabet]

Thanks guys for your input. I've managed to resolve it on my own.