C Variables, Constants and Literals

In the previous tutorial you learnt about C comments. Now, let's learn about variables, constants and literals in 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). Variable names are just the symbolic representation of a memory location. For example:

int age = 25;

Here, age is a variable of int type and we have assigned an integer value 25 to it.

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

char ch = 'a';
// some code
ch = 'l';

Visit this page to learn more about different types of data a variable can store.

int number = 5;      // integer variable
number = 5.5;        // error
double number;       // error

Constants

If you want to define a variable whose value cannot be changed, you can use the const keyword. This will create a constant. For example,

const double PI = 3.14;

Notice, we have added keyword const.

Here, PI is a symbolic constant; its value cannot be changed.

const double PI = 3.14;
PI = 2.9; //Error

You can also define a constant using the #define preprocessor directive. We will learn about it in C Macros tutorial.

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.

1. 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:

• decimal (base 10)
• octal (base 8)
• hexadecimal (base 16)

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.

2. 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

3. Characters

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

4. String Literals

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

"good"                  //string constant
""                     //null string constant
"      "               //string constant of six white space
"x"                    //string constant having a single character.
"Earth is round\n"         //prints string with a newline

5. 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.

For example: \n is used for a newline. The backslash \ causes escape from the normal way the characters are handled by the compiler.