Question

Define variable? Explain its declaration and initialization in C program.

Answer 1

C variables are names used for storing a data value to locations in memory. The value stored in the c variables may be changed during program execution.

C is a strongly typed language. Every variable must be declared, indicating its data type before it can be used. The declaration can also involve explicit initialization, giving the variable a value; a variable that is declared but not explicitly initialized is of uncertain value (and should be regarded as dangerous until it is initialized). In K&R C, declarations must precede all other statements, but in modern versions of C, this rule is relaxed so that you don't have to declare a variable until just before you start using it:

The basic form of a variable declaration is shown here:

type identifier [ = value][, identifier [= value] ...] ;

The type is one of C's data types like int, chat, double etc.

The identifier is the name of the variable. You can initialize the variable by specifying an equal sign and a value. Keep in mind

You can initialize the variable by specifying an equal sign and a value. Keep in mind that the initialization expression must result in a value of the same (or compatible) type as that specified for the variable.

To declare more than one variable of the specified type, use a comma-separated list.

Declaration of Variable

Declaration of variable in c can be done using following syntax:

data_type variable_name;
or
data_type variable1, variable2,…,variablen;

where data_type is any valid c data type and variable_name is any valid identifier.

For example,

int a; float variable; float a, b;

Initialization of Variable

C variables declared can be initialized with the help of assignment operator ‘=’.

Syntax

data_type variable_name=constant/literal/expression;
or
variable_name=constant/literal/expression;

Example:

int a=10; int a=b+c; a=10; a=b+c;

Multiple variables can be initialized in a single statement by single value, for example, a=b=c=d=e=10;

NOTE: C variables must be declared before they are used in the c program. Also, since c is a case-sensitive programming language, therefore the c variables, abc, Abc and ABC are all different.

int Variable Declaration and Variable Initialization in two steps:

Save Source File Name as : IntExample.c Program/* C program to demonstrate Declaration and initialization C program to demonstrate int data type */ #include<stdio.h> void main() { int age; // Declaration of variable age age = 20; // initialization of the variable age printf("%d \n",age); }Output20 Press any key to continue . . . 

int Variable Declaration and Variable Initialization in one line:

/* C program to demonstrate Declaration and initialization C program to demonstrate int data type */ #include<stdio.h> void main() { int age=20; // Declaration and initialization of variable age printf("%d \n",age); }Output20 Press any key to continue . . .

Multiple variables can be initialized in a single statement by single value

a=b=c=d=e=10;/* C program to demonstrate Declaration and initialization C program to demonstrate int data type */ #include<stdio.h> void main() { int a, b, c, d, e; // Declaration of variable a=b=c=d=e=10; // initialization of variable printf("%d \n",a); printf("%d \n",b); printf("%d \n",c); printf("%d \n",d); printf("%d \n",e); }Output10 10 10 10 10 Press any key to continue . . .

Point To remember

Variables should be declared in the C program before to use.

Memory space is not allocated for a variable while declaration. It happens only on the variable definition.

Variable initialization means assigning a value to the variable.

 Type 

Syntax

Variable declaration

data_type variable_name;
Example: int x, y, z; char flat, ch;

Variable initialization

data_type variable_name = value;

Example: int x = 50, y = 30; char flag = ‘x’, ch=’l’

Answer 2

Definition of variable and explanation of its declaration and initialization in C program are as follow:

• A variable refers to a storage area that our programs can manipulate in C. Variables tend to have a specific type. The type defines the size and layout of the variable's memory. Some of the types would be: char, int, float, double etc.

• Initialization: It means assigning a value to the variable. The general syntax would be: data_type variable_name = value;

• Declaration: Variables are declared first, then they are sent to the main program for use. At the time of declaration, Memory space is not allocated for a variable. The general syntax would be: data_type variable_name;