C - Real number validation

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int valid=validate_numbers(char number[]);
///////////////////////////////////////////////////
int main() {

    char chain[20];
    float N;
    int valid=0;

    do{
        printf("introduce real numbers: ");
        fgets(chain, sizeof(chain), stdin);
        if( chain[strlen(chain)-1] == '\n')
            chain[strlen(chain)-1] = '\0';
        valid=validate_numbers(chain);
    }while(valid==0);

    N=atof(chain);

    printf("the float number is: %.2f", N);

    getche();

    return 0;
}
///////////////////////////////////////////////////
int valid=validate_numbers(char number[])
{
    int i, long, count=0;
    long = strlen(number);
    for(i=0; i<strlen(number); i++)
    {
        if(!( (number[i]>=48 && number[i]<=57) || number[i]==46 || number[i]==45 ) )
        {
            printf("JUST NUMBERS\n");
            return 0;
        }

        if(number[i]==46){
            count++;
            if(count>=2){
                printf("INTRODUCE A VALID NUMBER\n");
                return 0;
            }
        }

        if(i>0 && number[i]==45){
            printf("INTRODUCE A VALID NUMBER\n");
            return 0;
        }

        if( long=1 && (number[0]==45 || number[0]==46) ){
            printf("INTRODUCE A VALID NUMBER\n");
            return 0;
        }

        if(long==2 && number[0]==45 && number[1]==46){
            printf("INTRODUCE A VALID NUMBER\n");
            return 0;
        }
    }
    return 1;
}