C++ function clarification please?

A few things The first thing - it's your choice, but for me, it makes sense to have the functions declared BEFORE int main(). Like this: //Declare function for outputting age. int showAge(int age) { while(a... } //Declare function for error checking. int ageCheck(int check) { while( .... } int main() { //Declare needed variables. const int LOW = 1; ... } This eliminates the need for void showAge(int); void ageCheck(int); Also you need const int LOW = 1; const int HIGH = 100; outside of int main. The functions are outside of int main, so they can't access them. Why do you have while loops in your functions? If statements would be much better as they won't return an endless stream of " You are __ years old." '0' and '9' shouldn't be in single quotes. age is an int, not a char or string. Why are showAge and ageCheck ints? They don't return anything. They should be void showAge(int age) and void ageCheck(int AGE). As you see, I changed int check to int age. You are using age in the function ageCheck, not check, so change one. I missed a bunch probably, so this is what I changed the code to: #include <iostream> #include <string> using namespace std; const int LOW = 1; const int HIGH = 100; //Declare function for outputting age. int showAge(int age) { if(age >= LOW && age <= HIGH) { cout << "You are " << age << " years old!" << endl; } } //Declare function for error checking. int ageCheck(int age) { if(age <= LOW || age >= HIGH) { cout << " " <<endl; } if(age < 0 || age > 9) { cout << "Please enter a valid age from 1 through 100: "; cin >> age; ageCheck(age); } else { showAge(age); } } int main() { //Declare needed variables. int age; //Get age from the user. cout << "Please enter your age from 1 through 100: "; cin >> age; showAge(age); ageCheck(age); return 0; }

Imagine you have a cursor that moves from line to line in your program, starting from main. It will get to showAge and then jump inside the function and continue from there. When the cursor reaches the end of the function, it will go back to the line after where the function was called. The function parameters (the variables between the parenthesis) will be copied into the function as if they were declared at the top. So in showAge, you will start with a variable called age which is a copy of the age that you passed into the function from main. This variable will disappear when the function ends. If you modify this copy, it will not affect the original variable that you passed in. To do that you will need to use pointers or references.

this should get you going: #include <iostream> #include <string> using namespace std; void showAge(int); void ageCheck(int); int main() { //Declare needed variables. const int LOW = 1; const int HIGH = 100; int age; //Get age from the user. cout << "Please enter your age from 1 through 100: "; cin >> age; showAge(age); ageCheck(age); return 0; } //Declare function for outputting age. void showAge(int age) { if(age > LOW || age < HIGH) { cout << "You are " << age << " years old!" << endl; } } //Declare function for error checking. void ageCheck(int check) { if(age < LOW || age > HIGH) { cout << " " <<endl; } while(age <LOW || age > HIGH) { cout << "Please enter a valid age from 1 through 100: "; cin >> age; } else { showAge(age); } }