Keywords in C programming Language

1. auto – The auto keyword is used to declare a type of variable in the C Programming language. It is the automatic variable and it is always a local variable only. This variable is declared either inside block or main.

Syntex

auto int var;

Example

auto int a=10;

Program

Output

The value within block: 5
the value within main: 10

The auto variable cannot be a global variable.

Default value of auto varIable is garbage value.

2. break – the break statement is mostly used in for loop  and while loop.

,Do while loop and switch statements

Syntex

break;

Program

Output

value of num is : 0
value of num is : 1
value of num is : 2
value of num is : 3
value of num is : 4
exit from while loop

3. continue –  the break statement is mostly used in for loop,while loop do while and switch -case statements.

Syntex

continue;

Example

Output

1
2
3
4
6
7
8
9
10

4. switch and case – swith and case statements are used to execute a block code among multiple statements. likes if … else… if statements

Syntex

switch(expression)
{
case '1';
//some codes to execute when 1
break;
case '2';
//some codes to execute when 2
break;
....................
....................
case 'n';
//some codes to execute when n
break;

}

6. default – default is used to switch -case statements

Syntex

default;

7. char – The char keyword declares a character variable. – variable declaration

Syntex

char char_name='value';

Example

char alphabet='A';

8. const – cons is a keyword that assigns an initial value to the variable that cannot be changed by the programmer. – variable declaration.

Syntex

const variable_name=value;

const my_age=22;

9. do – Do is a keyword in c which is commonly used  with do- while loop. It looks like other programming languages.

Syntex

do-while(expression)

Example

10. while –  while is a keyword in C language which is used to execute a loop statement. While statement executes repeatedly until statement becomes false

Syntex

while(expression)

Example

Output
1
2
3
4

11. double – double is a keyword in C language which is used to represents floating point value.

Syntex

double value;   - variable declaration

Example

double salary=23123.56;

12.float -float is a keyword in C language which is used to represents single precision floating point data type.  – variable declaration.

float value;

13. if –  if is a keyword in C language which is used for conditional statements execution. If evaluates expression and when it becomes true(nonzero), statement is executed.  Otherwise, when evaluation  becomes false(zero), statement of if is skipped.

The basic form syntex of if

Syntex

if(checkExpression)
statement1

14. else – If statements may be used together with else. When if statement becomes false(zero), else execute the statement.

Syntex

if(checkExpression)
statement1
else
statement2

Example

16. extern –  extern keyword is used for declaring external variables in C. This modifier is used with all data types like int , float, double, array, pointer, structure, function

Syntex

extern data_declaration;

Example

extern int a;

17. for –  For is a keyword  which is used to repeat looping statements in C Language.

Syntex

for(initialization, Boolean Expresion, increment or dicrement){
// statement(s)
}

Example

output

0 1 2 3 4 5 6 7 8 9

18. goto –

goto is a keyword that is used to jumb directly to labled statement when a problem is encountered.

Syntax

goto label_name;
statement(s);
...................
label_name: statements(s)

Example

20. short –  Short is a key word  that is a data type in C. We can use short in following types.

short int ;
un signed short int;
signed short int;

21. long – long is a key word that is a data type in C. We can use long in following types.

long long  int ;
un signed long int;
signed slong int;

22. signed and unsigned – Signed keyword is used to store negative or positive values

Syntex.

signed data_diclaration;
unsigned data_diclaration;

23. return – return is a keyword that is used to return the value  and terminate the function

int function_name()
{
int x=10;
return x;
}

24.sizeof –The size of is a keyword that evaluates the size of data types

Example

Output

 1
4
4
8

25. register – register keyword is used to define local variables.

Syntex

register data_declaration;

Example

register int age;

26. static – static keyword used for variable declaration and method declaration

Syntex

static data_diclaration;

static function_diclaration;

27. struct – struct is a keyword that is used to create a structure. Structure is a user-defined data type used to store a group of variable in a single record.

The syntax of struct

struct [struct_name]
{
[type1_variable_name];
[type2_variable_name];
………………………………
}

Example

29. union – union means one or more variable used declare a single unit like struct (Structure in C) . Except it allows you to define variables that share  storage space.

Syntex of union keyword

union [union_type_name]
{
data_type diclaration;
}

Example

union student
{
int age;
char name[];
}

30. void – void is a keyword in C Language which is used as a function to return type. Void means that the function can never return a value.

Syntex of void keyword

void function_name(parameter_list)
{
//statement(s)
}

Example for void

void hello(char *name)
{
printf (“hello, %s”,name);
}

Syntex

syntex of the volatile key word

volatile data_type;