Number, Letters and Space Only allowed.

[arveen11]

hey guys.. i just want your help.. because i am making a program that has only numbers, letters, and space should be allowed.. i dont know the syntax for the space and for the numbers >.<

i already made this program but only characters and backspace allowed..

here is the code:

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <ctype.h>

int main(){

	char *letter;
	char hold;
	int ctr = 0;
	char *holdLetter;
    letter = (char*)malloc(sizeof(char));
	holdLetter = letter;
	printf("Enter String Letter: ");
	do
    {
    hold = getch();
    if(isalpha(hold))
    {
                     *holdLetter = hold;
                     printf("%c", *holdLetter);
                     holdLetter++;
                     ctr++;
                     *holdLetter = 0;
                     }
                     else if(hold == 8 && ctr!= 0)
                          {
                            printf("\b \b");
                            ctr--;
                            holdLetter--;
                             }
                     }while(hold !=13);
                     *holdLetter = 0;
                     free(holdLetter);
                     
                     printf("\nLetters are : %s", letter);
                     
                     
                     
	getch();
	return 0;
}

any hints there sir??

can someone help me with space and number? T_T