Variables in C

What is variable

• A variable in a program is a specific piece of memory that consists of one or more contiguous bytes, typically 1, 2, 4, 8 or 16 bytes.
• Every variable has a type that specifies the kind of data the variable can store.
• The type of a variable determines how many bytes are allocated for it.
• Every variable in a program has a name, which will correspond to the memory address for the variable.
• You use the variable name to store a data value in memory or retrieve the data that the memory contains.
• The value of a variable isn’t fixed, and you can change it whenever you need to throughout a program.

Rules for naming variables

• A variable name is a sequence of one or more uppercase or lowercase letters, digits, and underscore characters (_) that begin with a letter (incidentally, the underscore character counts as a letter).
• A variable name must not begin with a digit.
• A variable name must not include characters other than letters, underscores, and digits.
• Variables starting with one or two underscore characters are often used in the header files, so don’t use the underscore as the first character in your variable names.
• Variable names is that they are case sensitive. 

Notes:

• The maximum number of characters that you can have in a variable name will depend on your compiler.
• A minimum of 31 characters must be supported by a compiler that conforms to the C standard.

Types of variables

The type of a variable is determined by the its data type while declaring the variable. Variables can be of several type from simple type to complex type.

(a).Integer type variables

·         Used to store integer values.

·         Type is int.

·         Example : int marks=98;

(b).Real type variables

·         Are used to store real numbers.

·         Type is float, double etc.

·         Example : float rate=12.5;

(c).Char type variables

·         Used to character values.

·         Type is char.

·         Example : char grade=’A’;

(d).Complex type variables

·         Like struct,union type;

Variable declaration

Variable declaration specifies the variable name and type of data that variable will store.

Syntax for declaring a variable:

dataType variableName;

example : int salary;  // variable declaration

This statement is called a variable declaration because it declares the name of the variable.

Note that a variable declaration ends with a semicolon. If you omit the semicolon, your program will generate an error when you try to compile it.

Assigning value to a variable

The assignment operator(=) is used to assign value to a variable;

Example

int marks=98;

char grade=’A’;

float rate=12.5;

//Program to ask user their marks and then display the marks.

#include<stdio.h>

int main(){

  int marks;

  printf(Enter marks:“”);

  scanf(“%d”,marks);

  printf(“Your marks are %d.”,marks);

 return 0;

}

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