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• C++ Variables, Literals and Constants
• C++ Data Types
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• Python Strings

C++ Variables, Literals and Constants

In this tutorial, we will learn about variables, literals, and constants in C++ with the help of examples.

Content from https://www.programiz.com/cpp-programming/variables-literals.

C++ Variables

In programming, a variable is a container (storage area) to hold data.

To indicate the storage area, each variable should be given a unique name (identifier). For example,

int age = 14;

Here, age is a variable of the int data type, and we have assigned an integer value 14 to it.

Note: The int data type suggests that the variable can only hold integers. Similarly, we can use the double data type if we have to store decimals and exponentials.

We will learn about all the data types in detail in the next tutorial.

The value of a variable can be changed, hence the name variable.

int age = 14;   // age is 14
age = 17;       // age is 17

Rules for naming a variable

Note: We should try to give meaningful names to variables. For example, first_name is a better variable name than fn.

C++ Literals

Literals are data used for representing fixed values. They can be used directly in the code. For example: 1, 2.5, 'c' etc.

Here, 1, 2.5 and 'c' are literals. Why? You cannot assign different values to these terms.

Here's a list of different literals in C++ programming.

Integers

An integer is a numeric literal(associated with numbers) without any fractional or exponential part. There are three types of integer literals in C programming:

For example:

Decimal: 0, -9, 22 etc
Octal: 021, 077, 033 etc
Hexadecimal: 0x7f, 0x2a, 0x521 etc

In C++ programming, octal starts with a 0, and hexadecimal starts with a 0x.

Floating-point Literals

A floating-point literal is a numeric literal that has either a fractional form or an exponent form. For example:

-2.0

0.0000234

-0.22E-5

Note: E-5 = 10-5

Characters

A character literal is created by enclosing a single character inside single quotation marks. For example: 'a', 'm', 'F', '2', '}' etc.

Escape Sequences

Sometimes, it is necessary to use characters that cannot be typed or has special meaning in C++ programming. For example, newline (enter), tab, question mark, etc.

In order to use these characters, escape sequences are used.

String Literals

A string literal is a sequence of characters enclosed in double-quote marks. For example:

We will learn about strings in detail in the C++ string tutorial.

C++ Constants

In C++, we can create variables whose value cannot be changed. For that, we use the const keyword. Here's an example:

const int LIGHT_SPEED = 299792458;
LIGHT_SPEED = 2500 // Error! LIGHT_SPEED is a constant.

Here, we have used the keyword const to declare a constant named LIGHT_SPEED. If we try to change the value of LIGHT_SPEED, we will get an error.

A constant can also be created using the #define preprocessor directive. We will learn about it in detail in the C++ Macros tutorial.

C++ Data Types

In this tutorial, we will learn about basic data types such as int, float, char, etc. in C++ programming with the help of examples.

In C++, data types are declarations for variables. This determines the type and size of data associated with variables. For example,

int age = 13;

Here, age is a variable of type int. Meaning, the variable can only store integers of either 2 or 4 bytes.

C++ Fundamental Data Types

The table below shows the fundamental data types, their meaning, and their sizes (in bytes):

Now, let us discuss these fundamental data types in more detail.

1. C++ int

int salary = 85000;

2. C++ float and double

float area = 64.74;
double volume = 134.64534;

As mentioned above, these two data types are also used for exponentials. For example,

double distance = 45E12    // 45E12 is equal to 45*10^12

3. C++ char

char test = 'h';

Note: In C++, an integer value is stored in a char variable rather than the character itself. To learn more, visit C++ characters.

4. C++ wchar_t

wchar_t test = L'ם'  // storing Hebrew character;

Notice the letter L before the quotation marks.

Note: There are also two other fixed-size character types char16_t and char32_t introduced in C++11.

5. C++ bool

bool cond = false;

6. C++ void

Note: We cannot declare variables of the void type.

Putting it all together

Run the following repl to see its results. Looking at the main.cpp file, a range of variables of different data types are declared at the top.

cout is used with the + operator to output the sum of two integers. cout is also used to display a message that includes the contents of the string variables, and lastly an if statement is used to present a message based on which letter is stored in the char variable.

Try doing each of the following, running the between each change:

1. Change the string variables to reflect your name
2. Change the values of the integers
3. Change the operator used in the output to *
4. Change the letter stored in the char variable to a grade you would like to receive
5. Change the integer variables to float, and assign decimal values.

C++ Type Modifiers

We can further modify some of the fundamental data types by using type modifiers. There are 4 type modifiers in C++. They are:

We can modify the following data types with the above modifiers:

C++ Modified Data Types List

Let's see a few examples.

long b = 4523232;
long int c = 2345342;
long double d = 233434.56343;
short d = 3434233; // Error! out of range
unsigned int a = -5;    // Error! can only store positive numbers or 0

Derived Data Types

Data types that are derived from fundamental data types are derived types. For example: arrays, pointers, function types, structures, etc.

We will learn about these derived data types in later tutorials.

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