This document provides an overview of keywords in the C programming language, explaining their reserved nature and usage in code. It covers several keywords such as 'auto', 'break', 'continue', 'switch', 'char', 'const', 'enum', 'extern', and others, detailing their functions, examples, and the implications of using them. The document serves as a foundational guide for understanding variable declarations, control statements, and data types in C.

1. Presented By
MR. SURAJ KUMAR
BCA, PGDCA & MCA
Mob- 7677308200
Email- suraj0616@gmail.com
LECTURE-2

2. Keywords

3. Keyword
Keywords are predefined, reserved words used in
programming that have special meanings to the
compiler. Keywords are part of the syntax and they
cannot be used as an identifier.
The keywords cannot be used as variable names
because if we do so, we are trying to assign a new
meaning to the keyword, which is not allowed by the
computer.

4. Keywords in C
auto break case char
const continue default do
double else enum extern
float for goto if
int long register return
short signed sizeof static
struct switch typedef union
unsigned void volatile while

5. auto
The auto keyword declares automatic variables. For
example:
auto int var1;
This statement suggests that var1 is a variable of storage
class auto and type int.
Variables declared within function bodies are automatic by
default. They are recreated each time a function is executed.
Since automatic variables are local to a function, they are
also called local variables.

6. break and continue
The break statement terminates the innermost loop
immediately when it's encountered. It's also used to
terminate the switch statement.
The continue statement skips the statements after it inside
the loop for the iteration.
for (i=1;i<=10;++i) {
if (i==4)
continue;
if (i==7)
break;
printf("%d ",i);
}
Output: 1 2 3 5 6

7. When i is equal to 4, the continue statement comes into
effect and skips 4. When i is equal to 7, the break
statement comes into effect and terminates the for
loop.

8. switch, case and default
The switch and case statement is used when a block of
statements has to be executed among many blocks. For
example:
switch(expression)
{
case '1':
//some statements to execute when 1
break;
case '5':
//some statements to execute when 5
break;
default:
//some statements to execute when default;
}

9. char
The char keyword declares a character variable. For
example:
char alphabet;
Here, alphabet is a character type variable.
const
An identifier can be declared constant by using the
const keyword.
const int i = 5;

10. do….while
int i;
do
{
printf("%d ",i);
i++;
}
while (i<10)

11. double and float
Keywords double and float are used for declaring
floating type variables. For example:
float number;
double longNumber;
Here, number is a single-precision floating type
variable whereas, longNumber is a double-precision
floating type variable.

12. if and else
Keywords double and float are used for declaring
floating type variables. For example:
float number;
double longNumber;
Here, number is a single-precision floating type
variable whereas, longNumber is a double-precision
floating type variable.

13. enum
enum
Enumeration types are declared in C programming
using keyword enum. For example:
enum suit
{
hearts;
spades;
clubs;
diamonds;
};
Here, an enumerated variable suit is created having
tags: hearts, spades, clubs, and diamonds.

14. extern
The extern keyword declares that a variable or a
function has external linkage outside of the file it is
declared.
for
There are three types of loops in C programming. The
for loop is written in C programming using the
keyword for. For example:
for (i=0; i< 9;++i)
{
printf("%d ",i);
}
Output: 0 1 2 3 4 5 6 7 8

15. goto
The goto statement is used to transfer control of the
program to the specified label. For example:
for(i=1; i<5; ++i)
{
if (i==10)
goto error;
}
printf("i is not 10");
error:
printf("Error, count cannot be 10.");
Output: Error, count cannot be 10.

16. int
The int keyword is used to declare integer type
variables. For example:
int count;
Here, count is an integer variable.
short, long, signed and unsigned
The short, long, signed and unsigned keywords are
type modifiers that alter the meaning of a base data
type to yield a new type.
short int smallInteger;
long int bigInteger;
signed int normalInteger;
unsigned int positiveInteger;

17. Range of int data types
Data types Range
short int -32768 to 32767
long int -2147483648 to 214743648
signed int -32768 to 32767
unsigned int 0 to 65535

18. return
The return keyword terminates the function and
returns the value.
int func()
{
int b = 5;
return b;
}
This function func() returns 5 to the calling
function.

19. sizeof
The sizeof keyword evaluates the size of data (a
variable or a constant).
#include <stdio.h>
int main()
{
printf("%u bytes.",sizeof(char));
}
Output: 1 bytes.

20. register
The register keyword creates register variables
which are much faster than normal variables.
For example:
register int var1;
static
The static keyword creates a static variable. The
value of the static variables persists until the end
of the program. For example:
static int var;

21. struct
The struct keyword is used for declaring a
structure. A structure can hold variables of
different types under a single name.
struct student
{
char name[80];
float marks;
int age;
} s1, s2;

22. typedef
The typedef keyword is used to explicitly associate a
type with an identifier.
typedef float kg;
kg bear, tiger;
union
A union is used for grouping different types of variables
under a single name.
union student
{
char name[80];
float marks;
int age;
}

23. void
The void keyword meaning nothing or no value.
void testFunction(int a)
{
.....
}
Here, the testFunction() function cannot return a value
because its return type is void.

24. volatile
The volatile keyword is used for creating volatile
objects. A volatile object can be modified in an
unspecified way by the hardware.
const volatile number
Here, number is a volatile object.
Since number is a constant, the program cannot
change it. However, hardware can change it since it is a
volatile object.