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Fundamentals of C++

Fundamentals of C++

Learn commonly used data types and operators in C++.

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Data types in C++

Every variable in C++ needs to be declared with the help of a data type. For example, whether a variable can store only numbers or can also store other symbols as its value.

Common data types

The following are the commonly used data types in C++:

  • int: Integer values (5, 0, -1, etc.)

  • double: Floating-point values (2.33333, -2500.001, 20.0, etc.)

  • bool: Boolean values (true/1, false/0)

  • char: Character value (a, 0, $, etc)

  • string: String values (educative, c++, k2, etc.)

The bool data type is used to store true or false, but whenever we display the Boolean values, true is displayed as 1 and false as 0. In order to use the string data type, we have to add #include <string> at the start of the code.

Variable declaration

The C++ language requires the programmer to tell the data type of the variables used in a program. The following code demonstrates the declaration of variables to input their values with a suitable prompt and to display them with suitable labels:

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

int main()
{
   string str; // Declaring a variable of type string
   int number; // Declaring a variable of type integer
   double real; // Declaring a variable of type double
   bool isTrue; // Declaring a variable of type bool
   char letter; // Declaring a variable of type char

   cout << "Please input a word: ";
   cin >> str;
   cout << "Please input an integer: ";
   cin >> number;
   cout << "Please input a real number: ";
   cin >> real;
   cout << "Please input 0 or 1 [0 for false, 1 for true]: ";
   cin >> isTrue;
   cout << "Please input a letter: ";
   cin >> letter;
   cout << "The value of each variable is enclosed in brackets:" << std::endl;
   cout << "str (" << str << ")" << endl;
   cout << "number (" << number << ")" << endl;
   cout << "real number (" << real << ")" << endl;
   cout << "isTrue (" << isTrue << ")" << endl;
   cout << "letter (" << letter << ")" << endl;
   return 0;
}
Variable declaration

Note: We don’t use < and > with string other than #include because it’s a data type. The string at line 2 is the name of the file that defines the string data type.

Explanation

  • Line 7–11: We declare the variables so they can be used to store the values input by the user. There are different types of variables that are declared:
    • str is a variable of the string type.
    • number is a variable of the int type.
    • fraction is a variable of the double type.
    • isTrue is a variable of the bool type.
    • letter is a variable of the char type.
  • Line 13–22: We output a prompt using cout and demand input from the user using cin and then store them in the relevant variable.
  • Line 24–28: We output the variable
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