Variable Declaration and Initialization in C: A Comprehensive Guide
Table of Content:
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 ProgramOutput/* C program to demonstrate Declaration and initialization C program to demonstrate int data type */ #include void main() { int age; // Declaration of variable age age = 20; // initialization of the variable age printf("%d \n",age); }
20 Press any key to continue . . .
int Variable Declaration and Variable Initialization in one line:
Output/* C program to demonstrate Declaration and initialization C program to demonstrate int data type */ #include void main() { int age=20; // Declaration and initialization of variable age printf("%d \n",age); }
20 Press any key to continue . . .
Multiple variables can be initialized in a single statement by single value
a = b = c = d = e = 10;
Output/* C program to demonstrate Declaration and initialization C program to demonstrate int data type */ #include 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); }
10 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’;
|