How do I only allow numbers

Hello, I just need the function that only allows numbers to be used for a random numbers game.
Here is the code

Code:

#include <stdio.h>

startGuessing()
{
	//this function is where the guessing game launches from

	int i=0,r=0, y=1;

	r=rand(time(0))%100+1;
    printf("The Number is between 1 and 100\n");
	do
	{

	printf("What is your guess?:");
	scanf("%d",&i);	
    if(i>100)
	     {
         printf("You have entered an invalid number. The Number is between 1 and 100.\n");
         continue;
         }
    else if(i<1)
         {
         printf("You have entered an invalid number. The Number is between 1 and 100.\n");
         continue;
         }
	else if(i>r)
		{
		printf("You are too high. Try again.\n");
		continue;
		}
	else if(i<r)
		{
		printf("You are too low. Try again.\n");
		continue;
		}

	else
		{
		printf("You are correct!\n");
		break;
		}
	y++;
	}
	while(y<100);

return 0;

}

startDice()
{
	//this function is where the dice game launches from
	printf("You have chosen to play 5 ROLLS! The object of the game is to roll 3 even numbers with only 5 rolls. Lets Start!\n\n");
	
	int a=0, b=0, c=0, d=0, e=0, f=0;
	
    a=rand(time(0))%6+1, b=rand(time(0))%6+1, c=rand(time(0))%6+1, d=rand(time(0))%6+1, e=rand(time(0))%6+1;
    
    printf("To roll, "); system("PAUSE");
    printf("You rolled %d for roll one.\n\n",a);
    printf("To roll again, "); system("PAUSE");
    printf("You rolled %d for roll two.\n\n",b);
    printf("To roll again, "); system("PAUSE");
    printf("You rolled %d for roll three.\n\n",c);
    printf("To roll again, "); system("PAUSE");
    printf("You rolled %d for roll four.\n\n",d);
    printf("To roll again, "); system("PAUSE");
    printf("You rolled %d for roll five.\n\n",e);
    
    int rA=0, rB=0, rC=0, rD=0, rE=0;
    
    rA=a%2;
    rB=b%2;
    rC=c%2;
    rD=d%2;
    rE=e%2;
    
    f=rA+rB+rC+rD+rE;
    
    if(f<3)
    {
    printf("You won!!!\n\n");
    }
    else
    {
    printf("You lose.\n\n");
    }
}

printMenu()
{
	int input=0;
	do {
		//print the menu
		printf("Please select your game: \n\n");
		printf("\t1: Guessing Game\n");
		printf("\t2: Dice Game\n");
		printf("\t-1: Exit Program\n");
		
		//take the user's input
		scanf("%d",&input);
		
		//check to see which game the user wants
		if (input==1) {
			startGuessing();
		}
		else if(input==2)
		{
			startDice();
		}
		
		//if the user enters -1, exit the loop (and thus the program)
	} while (input!=-1);
}

int main (void)
{
	//this seeds the system's time into the random generator
	srand(time(0));
	printf("\nA M A Z I N G  G A M E    v1.0\n");
	
	//load the main menu
	printMenu();
}

First of all don't forget to return 0 from main. Compile your code with all the warnings enabled.

In terms of making sure you only read in numbers you basically have to read the input as a string and then use strtol() to check that the input is a valid number. After that continue to check if it is in the range you want it.

I assume you want the user to be able to type in a value, but you want to make sure it's numeric only.

The general way this is achieved is to use fgets() to read a line and convert it with strtol(). strtol() can help you figure out if the user typed something invalid, in which case you can ask again.