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Tip of the Day
Language: C++
Expertise: Beginner
Jun 25, 2003

Declaring Variables in C++

Say you want to store data for temporary use in a program. You will have to declare variables to input the data. Luckily, declaring variables in C++ is very easy. This simple program gets the user's age as input and displays it back to the screen. Here is the source code:

#include <iostream>
using namespace std;

int main()
{
   int age;

   cout << "My Second C++ Program" <<' endl;
   cout << "Please enter your age in years followed by <enter>: ";
   cin >> age;
   cout << "\nYou are " << age << " years old." << endl;

   return 0;
}
To declare the variable "age," simply type the data type (int) in front of it. Notice that you can specify the type of data you want the function main to return. This next program uses a few more variables. It retrieves the user's age, as well as their height, weight, hair color, and eye color.

#include <iostream>
#include <string>
using namespace std;

int main()
{
   int age, feet, inches, pounds;
   string hair, eye;

   cout << "My third c++ program.\n\n";
   cout << "Please type your answer to each question"
        << "followed by <enter>." << endl;
   cout << "What is your age (years)? ";
   cin >> age;
   cout << "\nHow tall are you (ft in)? ";
   cin >> feet >> inches;
   cout << "\nHow much do you weigh (lbs)? ";
   cin >> pounds;
   cout << "\nWhat color is your hair? ";
   cin >> hair;
   cout << "\nWhat color are your eyes? ";
   cin >> eye;

   cout << endl << "\nYou are " << age << " years old, "
        << feet << " feet " << inches << " inches tall."         << "\nYou
weigh " << pounds << " pounds,
        << " have " << hair << " colored hair and "
        << eye << " colored eyes." << endl;

   return 0;
}
Notice that it's possible to declare different variables of the same type in one line. Simply separate them by a comma. The previous code also includes a file called string and uses strings to store characters.

A note about data-handling and error detection: when you have an integer as a variable, there is nothing you can do to prevent a user from trying to enter invalid data.

Wael Salman
 
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