how to prompt user to input valid number in c code example

Example 1: how to get user input in c

#include <stdio.h>
//this is for storing numbers
int main(){
	
    int age; //this makes a vairable for you to store the value in
    printf("enter in your age: "); //this prints a prompt for the user
    scanf("%d", &age); //this takes in the argument given and stores it
                       //into the address of age

	return 0;
}

Example 2: check command line input is a number in c

bool isNumber(char number[])
{
    int i = 0;

    //checking for negative numbers
    if (number[0] == '-')
        i = 1;
    for (; number[i] != 0; i++)
    {
        //if (number[i] > '9' || number[i] < '0')
        if (!isdigit(number[i]))
            return false;
    }
    return true;
}