In this tutorial, you will learn about variables and rules for naming a variable. You will also learn about different literals in C programming and how to create constants.
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 playerScore = 95;
Here, playerScore is a variable of
int type. Here, the variable is assigned an integer value
The value of a variable can be changed, hence the name variable.
char ch = 'a'; // some code ch = 'l';
Rules for naming a variable
- A variable name can only have letters (both uppercase and lowercase letters), digits and underscore.
- The first letter of a variable should be either a letter or an underscore.
- There is no rule on how long a variable name (identifier) can be. However, you may run into problems in some compilers if the variable name is longer than 31 characters.
Note: You should always try to give meaningful names to variables. For example:
firstName is a better variable name than
C is a strongly typed language. This means that the variable type cannot be changed once it is declared. For example:
int number = 5; // integer variable number = 5.5; // error double number; // error
Here, the type of number variable is
int. You cannot assign a floating-point (decimal) value 5.5 to this variable. Also, you cannot redefine the data type of the variable to
double. By the way, to store the decimal values in C, you need to declare its type to either
Visit this page to learn more about different types of data a variable can store.
Literals are data used for representing fixed values. They can be used directly in the code. For example: 1, 2.5, ‘c’ etc.
2.5 and ‘c’ are literals. Why? You cannot assign different values to these terms.
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)
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
E-5 = 10
A character literal is created by enclosing a single character inside single quotation marks. For example: ‘a’, ‘m’, ‘F’, ‘2’, ‘}’ etc.
4. 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.
||Single quotation mark|
||Double quotation mark|
\n is used for a newline. The backslash
\ causes escape from the normal way the characters are handled by the compiler.
5. 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
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
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.