C Programming

#include <stdio.h>
int main()
{
/* my first program in C */
printf("Hello, World! n");
return 0;
}
Data types in C
1. Fundamental Data Types
 Integer types
 Floating Type
 Character types
2. Derived Data Types
 Arrays
 Pointers
 Structures
 Enumeration
Syntax for declaration of a variable
data_type variable_name;
Integer data types
Keyword int is used for declaring the variable with integer type. For example:
int var1;
Floating types
Variables of floating types can hold real values(numbers) such as: 2.34, -9.382 etc.
Keywords either float or double is used for declaring floating type variable. For example:
float var2;
double var3;
Here, both var2 and var3 are floating type variables.

In C, floating values can be represented in exponential for m as well. For example:
float var3=22.442e2
Character types
Keyword char is used for declaring the variable of character type. For example:
char var4='h';
Here, var4 is a variable of type character which is storing a character 'h'.
The size of char is 1 byte. The character data type consists of ASCII characters. Each
character is given a specific value. For example:
For, 'a', value =97
For, 'b', value=98
For, 'A', value=65
For, '&', value=33
For, '2', value=49
C Programming Input Output (I/O)
ANSI standard has defined many library functions for input and output in C language.
Functions printf() and scanf() are the most commonly used to display out and take
input respectively. Let us consider an example:
#include <stdio.h> //This is needed to run printf() function.
int main()
{
printf("C Programming"); //displays the content inside quotation
return 0;
}
Output
C Programming
Explanation of How this program work s
1. Every program starts from main() function.

2. printf() is a library function to display output which only works if #include<stdio.h>is
included at the beginning.
3. Here, stdio.h is a header file (standard input output header file) and #include is command to
paste the code from the header file when necessary. When compiler
encounters printf()function and doesn't find stdio.h header file, compiler shows error.
4. Code return 0; indicates the end of program. You can ignore this statement but, it is good
programming practice to use return 0;.
I/O of integers in C
#include<stdio.h>
int main()
{
int c=5;
printf("Number=%d",c);
return 0;
}
Output
Number=5
Inside quotation of printf() there, is a conversion format string "%d" (for integer). If
this conversion format string matches with remaining argument,i.e, c in this case, value
of c is displayed.
#include<stdio.h>
int main()
{
int c;
printf("Enter a numbern");
scanf("%d",&c);
return 0;
}
Output
Enter a number
4
Number=4
The scanf() function is used to take input from user. In this program, the user is asked
a input and value is stored in variable c. Note the '&' sign before c. &c denotes the
address of c and value is stored in that address.

I/O of floats in C
#include <stdio.h>
int main(){
float a;
printf("Enter value: ");
scanf("%f",&a);
printf("Value=%f",a); //%f is used for floats instead of %d
return 0;
}
Output
Enter value: 23.45
Value=23.450000
Conversion format string "%f" is used for floats to take input and to display floating
value of a variable.
I/O of characters and ASCII code
#include <stdio.h>
int main(){
char var1;
printf("Enter character: ");
scanf("%c",&var1);
printf("You entered %c.",var1);
return 0;
}
Output
Enter character: g
You entered g.
Conversion format string "%c" is used in case of characters.
ASCII code
When character is typed in the above program, the character itself is not recorded a
numeric value(ASCII value) is stored. And when we displayed that value by using "%c",
that character is displayed.
#include <stdio.h>
int main(){
char var1;
scanf("%c",&var1);
printf("You entered %c.n",var1);
/* n prints the next line(performs work of enter). */

printf("ASCII value of %d",var1);
return 0;
}
Output
Enter character:
g
103
When, 'g' is entered, ASCII value 103 is stored instead of g.
You can display character if you know ASCII code only. This is shown by following
example.
#include <stdio.h>
int main(){
int var1=69;
printf("Character of ASCII value 69: %c",var1);
return 0;
}
Output
Character of ASCII value 69: E
The ASCII value of 'A' is 65, 'B' is 66 and so on to 'Z' is 90. Similarly ASCII value of 'a' is
97, 'b' is 98 and so on to 'z' is 122.
Variations in Input for integer and floats
#include <stdio.h>
int main(){
int a,b;
float c,d;
printf("Enter two intgers: ");
/*Two integers can be taken from user at once as below*/
scanf("%d%d",&a,&b);
printf("Enter intger and floating point numbers: ");
/*Integer and floating point number can be taken at once from user as below*/
scanf("%d%f",&a,&c);
return 0;
}
Similarly, any number of input can be taken at once from user.

Arithmetic Operators
Operator Meaning of Operator
+ addition or unary plus
- subtraction or unary minus
* multiplication
/ division
% remainder after division( modulo division)
Example of working of arithmetic operators
/* Program to demonstrate the working of arithmetic operators in C. */
#include <stdio.h>
int main(){
int a=9,b=4,c;
c=a+b;
printf("a+b=%dn",c);
c=a-b;
printf("a-b=%dn",c);
c=a*b;
printf("a*b=%dn",c);
c=a/b;
printf("a/b=%dn",c);
c=a%b;
printf("Remainder when a divided by b=%dn",c);
return 0;
}
a+b=13
a-b=5
a*b=36
a/b=2
Remainder when a divided by b=1
Explanation
Here, the operators +, - and * performed normally as you expected. In normal
calculation, 9/4 equals to 2.25. But, the output is 2 in this program. It is because, a and

b are both integers. So, the output is also integer and the compiler neglects the term
after decimal point and shows answer 2 instead of 2.25. And, finally a%b is 1,i.e.
,when a=9 is divided by b=4, remainder is 1.
Suppose a=5.0, b=2.0, c=5 and d=2
In C programming,
a/b=2.5
a/d=2.5
c/b=2.5
c/d=2
Note : % operator can only be used with integers.
Increment and decrement operators
In C, ++ and -- are called increment and decrement operators respectively. Both of
these operators are unary operators, i.e, used on single operand. ++ adds 1 to operand
and -- subtracts 1 to operand respectively. For example:
Let a=5 and b=10
a++; //a becomes 6
a--; //a becomes 5
++a; //a becomes 6
--a; //a becomes 5
Difference between ++ and -- operator as postfix and prefix
When i++ is used as prefix(like: ++var), ++var will increment the value of var and then
return it but, if ++ is used as postfix(like: var++), operator will return the value of operand
first and then only increment it. This can be demonstrated by an example:
#include <stdio.h>
int main(){
int c=2,d=2;
printf("%dn",c++); //this statement displays 2 then, only c incremented by 1 to 3.
printf("%d",++c); //this statement increments 1 to c then, only c is displayed.
return 0;
}

Output
2
4
Assignment Operators
The most common assignment operator is =. This operator assigns the value in right
side to the left side. For example:
var=5 //5 is assigned to var
a=c; //value of c is assigned to a
5=c; // Error! 5 is a constant.
Operator Example Same as
= a=b a=b
+= a+=b a=a+b
-= a-=b a=a-b
*= a*=b a=a*b
/= a/=b a=a/b
%= a%=b a=a%b
Relational Operator
Relational operators checks relationship between two operands. If the relation is true, it
returns value 1 and if the relation is false, it returns value 0. For example:
a>b
Here, > is a relational operator. If a is greater than b, a>b returns 1 if not then, it returns
0.
Relational operators are used in decision making and loops in C programming.

Operator Meaning of Operator Example
== Equal to 5==3 returns false (0)
> Greater than 5>3 returns true (1)
< Less than 5<3 returns false (0)
!= Not equal to 5!=3 returns true(1)
>= Greater than or equal to 5>=3 returns true (1)
<= Less than or equal to 5<=3 return false (0)
Logical Operators
Logical operators are used to combine expressions containing relation operators. In C,
there are 3 logical operators:
Operator
Meaning of
Operator Example
&&
Logial
AND
If c=5 and d=2 then,((c==5) &&
(d>5)) returns false.
||
Logical
OR
If c=5 and d=2 then, ((c==5) || (d>5))
returns true.
!
Logical
NOT If c=5 then, !(c==5) returns false.
Explanation
For expression, ((c==5) && (d>5)) to be true, both c==5 and d>5 should be true but,
(d>5) is false in the given example. So, the expression is false. For
expression ((c==5) || (d>5)) to be true, either the expression should be true.
Since, (c==5) is true. So, the expression is true. Since, expression (c==5) is
true, !(c==5) is false.

Conditional Operator
Conditional operator takes three operands and consists of two symbols ? and : .
Conditional operators are used for decision making in C. For example:
c=(c>0)?10:-10;
If c is greater than 0, value of c will be 10 but, if c is less than 0, value of c will be -10.
Bitwise Operators
A bitwise operator works on each bit of data. Bitwise operators are used in bit level
programming.
Operators Meaning of operators
& Bitwise AND
| Bitwise OR
^ Bitwise exclusive OR
~ Bitwise complement
<< Shift left
>> Shift right
Bitwise operator is advance topic in programming . Learn more about bitwise operator in
C programming.

For example:
#include <stdio.h>
int main(){
int a;
float b;
double c;
char d;
printf("Size of int=%d bytesn",sizeof(a));
printf("Size of float=%d bytesn",sizeof(b));
printf("Size of double=%d bytesn",sizeof(c));
printf("Size of char=%d byten",sizeof(d));
return 0;
}
Output
Size of int=4 bytes
Size of float=4 bytes
Size of double=8 bytes
Size of char=1 byte
Example of conditional operator
#include <stdio.h>
int main(){
char feb;
int days;
printf("Enter l if the year is leap year otherwise enter 0: ");
scanf("%c",&feb);
days=(feb=='l')?29:28;
/*If test condition (feb=='l') is true, days will be equal to 29. */
/*If test condition (feb=='l') is false, days will be equal to 28. */
printf("Number of days in February = %d",days);
return 0;
}
Output
Enter l if the year is leap year otherwise enter n: l
Number of days in February = 29

Variables
Variables are memory location in computer's memory to store data. To indicate the
memory location, each variable should be given a unique name called identifier. Variable
names are just the symbolic representation of a memory location. Examples of variable
name: sum, car_no, count etc.
int num;
Here, num is a variable of integer type.
Rules for writing variable name in C
1. Variable name can be composed of letters (both uppercase and lowercase letters), digits and
underscore '_' only.
2. The first letter of a variable should be either a letter or an underscore. But, it is discou raged to
start variable name with an underscore though it is legal. It is because, variable name that starts
with underscore can conflict with system names and compiler may complain.
3. There is no rule for the length of length of a variable. However, the first 31 characters
of a variable are discriminated by the compiler. So, the first 31 letters of two variables in a
program should be different.
In C programming, you have to declare variable before using it in the program.
Constants
Constants are the terms that can't be changed during the execution of a program. For
example: 1, 2.5, "Programming is easy." etc. In C, constants can be classified as:
Integer constants
Integer constants are the numeric constants(constant associated with number) without
any fractional part or exponential part. There are three types of integer constants in C
language: decimal constant(base 10), octal constant(base 8) and hexadecimal
constant(base 16) .
Decimal digits: 0 1 2 3 4 5 6 7 8 9
Octal digits: 0 1 2 3 4 5 6 7
Hexadecimal digits: 0 1 2 3 4 5 6 7 8 9 A B C D E F.
For example:
Decimal constants: 0, -9, 22 etc
Octal constants: 021, 077, 033 etc

Hexadecimal constants: 0x7f, 0x2a, 0x521 etc
Notes:
1. You can use small caps a, b, c, d, e, f instead of uppercase letters while writing a hexadecimal
constant.
2. Every octal constant starts with 0 and hexadecimal constant starts with 0x in C programming.
Floating-point constants
Floating point constants are the numeric constants that has either fractional form or
exponent form. For example:
-2.0
0.0000234
-0.22E-5
Note :Here, E-5 represents 10-5. Thus, -0.22E-5 = -0.0000022.
Character constants
Character constants are the constant which use single quotation around characters. For
example: 'a', 'l', 'm', 'F' etc.
Escape Sequences
Sometimes, it is necessary to use newline (enter), tab, quotation mark etc. in the
program which either cannot be typed or has special meaning in C programming. In such
cases, escape sequence are used. For example: n is used for newline. The backslash (
) causes "escape" from the normal way the characters are interpreted by the
compiler.
Escape Sequences
Escape Sequences Character
n Newline
t Horizontal tab

String constants
String constants are the constants which are enclosed in a pair of double -quote marks.
For example:
"good" //string constant
"" //null string constant
" " //string constant of six white space
"x" //string constant having single character.
"Earth is roundn" //prints string with newline
Enumeration constants
Keyword enum is used to declare enumeration types. For example:
enum color {yellow, green, black, white};
Here, the variable name is color and yellow, green, black and white are the enumeration
constants having value 0, 1, 2 and 3 respectively by default.
Data types in C
1. Fundamental Data Types
 Integer types
 Floating Type
 Character types
2. Derived Data Types
 Arrays
 Pointers
 Structures
Syntax for declaration of a variable
data_type variable_name;
Integer data types
Keyword int is used for declaring the variable with integer type. For example:
int var1;

Floating types
Variables of floating types can hold real values(numbers) such as: 2.34, -9.382 etc.
Keywords either float or double is used for declaring floating type variable. For example:
float var2;
double var3;
Here, both var2 and var3 are floating type variables.
In C, floating values can be represented in exponential form as well. For example:
float var3=22.442e2
Difference between float and double
Generally the size of float (Single precision float data type) is 4 bytes and that of
double(Double precision float data type) is 8 bytes. Floating point variables has a
precision of 6 digits whereas the the precision of double is 14 digits.
Note : Precision describes the number of significant decimal places that a floating values
carries.
Character types
Keyword char is used for declaring the variable of character type. For example:
char var4='h';
Here, var4 is a variable of type character which is storing a character 'h'.
The size of char is 1 byte. The character data type consists of ASCII characters. Each
character is given a specific value. For example:
For, 'a', value =97
For, 'b', value=98
For, 'A', value=65
For, '&', value=33
For, '2', value=49
Here is the list of all ASCII characters in C language.
Qualifiers
Qualifiers alters the meaning of base data types to yield a n ew data type.

Size qualifiers:
Size qualifiers alters the size of basic data type. The keywords long and short are two
size qualifiers. For example:
long int i;
The size of int is either 2 bytes or 4 bytes but, when long keyword is used, that variable
will be either 4 bytes of 8 bytes. Learn more about long keyword in C programming. If
the larger size of variable is not needed then, short keyword can be used in similar
manner as long keyword.
Sign qualifiers:
Whether a variable can hold only positive value or both values is specified by sign
qualifiers. Keywords signed and unsigned are used for sign qualifiers.
unsigned int a;
// unsigned variable can hold zero and positive values only
It is not necessary to define variable using keyword signed because, a variable is signed
by default. Sign qualifiers can be applied to only int and char data types. For a int
variable of size 4 bytes it can hold data from -231 to 231-1 but, if that variable is defined
unsigned, it can hold data from 0 to 232 -1.
Constant qualifiers
Constant qualifiers can be declared with keyword const. An object declared by const
cannot be modified.
const int p=20;
The value of p cannot be changed in the program.
Volatile qualifiers:
A variable should be declared volatile whenever its value can be changed by some
external sources outside program. Keyword volatile is used to indicate volatile v ariable.

ANSI standard has defined many library functions for input and output in C language.
Functionsprintf() and scanf() are the most commonly used to display out and take
input respectively. Let us consider an example:
#include <stdio.h> //This is needed to run printf() function.
int main()
{
printf("C Programming"); //displays the content inside quotation
return 0;
}
Output
C Programming
Explanation of How this program work s
1. Every program starts from main() function.
2. printf() is a library function to display output which only works if #include<stdio.h>is
included at the beginning.
3. Here, stdio.h is a header file (standard input output header file) and #include is command to
paste the code from the header file when necessary. When compiler
encounters printf()function and doesn't find stdio.h header file, compiler shows error.
4. Code return 0; indicates the end of program. You can ignore this statement but, it is good
programming practice to use return 0;.
I/O of integers in C
#include<stdio.h>
int main()
{
int c=5;
return 0;

}
Output
Number=5
Inside quotation of printf() there, is a conversion format string "%d" (for integer). If
this conversion format string matches with remaining argument,i.e, c in this case, value
of c is displayed.
#include<stdio.h>
int main()
{
int c;
scanf("%d",&c);
return 0;
}
Output
Enter a number
4
Number=4
The scanf() function is used to take input from user. In this program, the user is asked
a input and value is stored in variable c. Note the '&' sign before c. &c denotes the
address of c and value is stored in that address.
I/O of floats in C
#include <stdio.h>
int main(){

float a;
printf("Enter value: ");
scanf("%f",&a);
printf("Value=%f",a); //%f is used for floats instead of %d
return 0;
}
Output
Enter value: 23.45
Value=23.450000
Conversion format string "%f" is used for floats to take input and to display floating
value of a variable.
I/O of characters and ASCII code
#include <stdio.h>
int main(){
char var1;
scanf("%c",&var1);
printf("You entered %c.",var1);
return 0;
}
Output
Enter character: g
You entered g.
Conversion format string "%c" is used in case of characters.

ASCII code
When character is typed in the above program, the character itself is not recorded a
numeric value(ASCII value) is stored. And when we displayed that value by using "%c",
that character is displayed.
#include <stdio.h>
int main(){
char var1;
scanf("%c",&var1);
printf("You entered %c.n",var1);
/* n prints the next line(performs work of enter). */
printf("ASCII value of %d",var1);
return 0;
}
Output
Enter character:
g
103
When, 'g' is entered, ASCII value 103 is stored instead of g.
You can display character if you know ASCII code only. This is shown by following
example.
#include <stdio.h>
int main(){
int var1=69;
printf("Character of ASCII value 69: %c",var1);

return 0;
}
Output
Character of ASCII value 69: E
The ASCII value of 'A' is 65, 'B' is 66 and so on to 'Z' is 90. Similarly ASCII value of 'a' is
97, 'b' is 98 and so on to 'z' is 122.
Click here to learn about complete reference of ASCII code .
More about Input/Output of floats and Integer
Variations in Output for integer an floats
Integer and floating-points can be displayed in different formats in C programming as:
#include<stdio.h>
int main(){
printf("Case 1:%6dn",9876);
/* Prints the number right justified within 6 columns */
printf("Case 2:%3dn",9876);
/* Prints the number to be right justified to 3 columns but, there are 4
digits so number is not right justified */
printf("Case 3:%.2fn",987.6543);
/* Prints the number rounded to two decimal places */
printf("Case 4:%.fn",987.6543);
/* Prints the number rounded to 0 decimal place, i.e, rounded to integer
*/
printf("Case 5:%en",987.6543);
/* Prints the number in exponential notation(scientific notation) */
return 0;
}
Output

Case 1: 9876
Case 2:9876
Case 3:987.65
Case 4:988
Case 5:9.876543e+002
Variations in Input for integer and floats
#include <stdio.h>
int main(){
int a,b;
float c,d;
printf("Enter two intgers: ");
/*Two integers can be taken from user at once as below*/
scanf("%d%d",&a,&b);
printf("Enter intger and floating point numbers: ");
/*Integer and floating point number can be taken at once from user as
below*/
scanf("%d%f",&a,&c);
return 0;
}
Similarly, any number of input can be taken at once from user.
C Programming Operators
Operators are the symbol which operates on value or a variable. For example: + is a operator to
perform addition.
C programming language has wide range of operators to perform various operations. For better
understanding of operators, these operators can be classified as: Arithmetic Operators

Operator Meaning of Operator
+ addition or unary plus
- subtraction or unary minus
* Multiplication
/ Division
% remainder after division( modulo division)
Example of working of arithmetic operators
/* Program to demonstrate the working of arithmetic operators in C. */
#include <stdio.h>
int main(){
int a=9,b=4,c;
c=a+b;
printf("a+b=%dn",c);
c=a-b;
printf("a-b=%dn",c);
c=a*b;
printf("a*b=%dn",c);
c=a/b;
printf("a/b=%dn",c);
c=a%b;
printf("Remainder when a divided by b=%dn",c);
return 0;
}

a+b=13
a-b=5
a*b=36
a/b=2
Remainder when a divided by b=1
Explanation
Here, the operators +, - and * performed normally as you expected. In normal
calculation, 9/4 equals to 2.25. But, the output is 2 in this program. It is because, a and b are
both integers. So, the output is also integer and the compiler neglects the term after decimal
point and shows answer 2 instead of 2.25. And, finally a%b is 1,i.e. ,when a=9 is divided by b=4,
remainder is 1.
Suppose a=5.0, b=2.0, c=5 and d=2
In C programming,
a/b=2.5
a/d=2.5
c/b=2.5
c/d=2
Note: % operator can only be used with integers.
Increment and decrement operators
In C, ++ and -- are called increment and decrement operators respectively. Both of these
operators are unary operators, i.e, used on single operand. ++ adds 1 to operand and -- subtracts
1 to operand respectively. For example:
Let a=5 and b=10
a++; //a becomes 6
a--; //a becomes 5
++a; //a becomes 6
--a; //a becomes 5
Difference between ++ and -- operator as postfix and prefix

When i++ is used as prefix(like: ++var), ++var will increment the value of var and then return
it but, if ++ is used as postfix(like: var++), operator will return the value of operand first and
then only increment it. This can be demonstrated by an example:
#include <stdio.h>
int main(){
int c=2,d=2;
printf("%dn",c++); //this statement displays 2 then, only c
incremented by 1 to 3.
printf("%d",++c); //this statement increments 1 to c then, only c is
displayed.
return 0;
}
Output
2
4
Assignment Operators
The most common assignment operator is =. This operator assigns the value in right side to the
left side. For example:
var=5 //5 is assigned to var
a=c; //value of c is assigned to a
5=c; // Error! 5 is a constant.
= a=b a=b
+= a+=b a=a+b

-= a-=b a=a-b
*= a*=b a=a*b
/= a/=b a=a/b
%= a%=b a=a%b
Relational Operator
Relational operators checks relationship between two operands. If the relation is true, it returns
value 1 and if the relation is false, it returns value 0. For example:
a>b
Here, > is a relational operator. If a is greater than b, a>b returns 1 if not then, it returns 0.
Relational operators are used in decision making and loops in C programming.
Operator Meaning of Operator Example
== Equal to 5==3 returns false (0)
> Greater than 5>3 returns true (1)
< Less than 5<3 returns false (0)
!= Not equal to 5!=3 returns true(1)
>= Greater than or equal to 5>=3 returns true (1)
<= Less than or equal to 5<=3 return false (0)
Logical Operators
Logical operators are used to combine expressions containing relation operators. In C, there are
3 logical operators:

Operator
Meaning of
Operator Example
&&
Logial
AND
If c=5 and d=2 then,((c==5) && (d>5))
returns false.
||
Logical
OR
If c=5 and d=2 then, ((c==5) || (d>5))
returns true.
!
Logical
NOT If c=5 then, !(c==5) returns false.
Explanation
For expression, ((c==5) && (d>5)) to be true, both c==5 and d>5 should be true but, (d>5)
is false in the given example. So, the expression is false. For expression ((c==5) || (d>5)) to
be true, either the expression should be true. Since, (c==5) is true. So, the expression is
true. Since, expression (c==5) is true, !(c==5) is false.
Conditional Operator
Conditional operator takes three operands and consists of two symbols ? and : . Conditional
operators are used for decision making in C. For example:
c=(c>0)?10:-10;
If c is greater than 0, value of c will be 10 but, if c is less than 0, value of c will be -10.
Bitwise Operators
A bitwise operator works on each bit of data. Bitwise operators are used in bit level
programming.
& Bitwise AND
| Bitwise OR
^ Bitwise exclusive OR
~ Bitwise complement

<< Shift left
>> Shift right
Bitwise operator is advance topic in programming . Learn more about bitwise operator in C
programming.
Other Operators
Comma Operator
Comma operators are used to link related expressions together. For example:
int a,c=5,d;
The sizeof operator
It is a unary operator which is used in finding the size of data type, constant, arrays, structure
etc. For example:
#include <stdio.h>
int main(){
int a;
float b;
double c;
char d;
printf("Size of int=%d bytesn",sizeof(a));
printf("Size of float=%d bytesn",sizeof(b));
printf("Size of double=%d bytesn",sizeof(c));
printf("Size of char=%d byten",sizeof(d));
return 0;
}
Output
Size of int=4 bytes
Size of float=4 bytes
Size of double=8 bytes
Size of char=1 byte
Conditional operators (?:)
Conditional operators are used in decision making in C pro gramming, i.e, executes different
statements according to test condition whether it is either true or false.

Syntax of conditional operators
conditional_expression?expression1:expression2
If the test condition is true, expression1 is returned and if false expression2 is returned.
Example of conditional operator
#include <stdio.h>
int main(){
char feb;
int days;
printf("Enter l if the year is leap year otherwise enter 0: ");
scanf("%c",&feb);
days=(feb=='l')?29:28;
/*If test condition (feb=='l') is true, days will be equal to 29. */
/*If test condition (feb=='l') is false, days will be equal to 28. */
printf("Number of days in February = %d",days);
return 0;
}
Output
Enter l if the year is leap year otherwise enter n: l
Number of days in February = 29
Other operators such as &(reference operator), *(dereference operator) and ->(member selection)
operator will be discussed in pointer chapter.

C Program to Print a Sentence
/* C Program to print a sentence. */
#include <stdio.h>
int main()
{
printf("C Programming"); /* printf() prints the content inside quotation
*/
return 0;
}
Output
C Programming
Explanation
Every C program starts executing code from main( ) function. Inside main( ), there is
a printf( )function which prints the content inside the quotation mark which is "C
Programming" in this case. Learn more about output in C programming language.
C Program to Print a Integer Entered by a User
#include <stdio.h>
int main()
{
int num;
printf("Enter a integer: ");
scanf("%d",&num); /* Storing a integer entered by user in variable
num */
printf("You entered: %d",num);
return 0;
}
Output
Enter a integer: 25
You entered: 25

C Program to Add Two Integers
In this program, user is asked to enter two integers and this program will add these two integers
and display it.
/*C programming source code to add and display the sum of two integers
entered by user */
#include <stdio.h>
int main( )
{
int num1, num2, sum;
printf("Enter two integers: ");
scanf("%d %d",&num1,&num2); /* Stores the two integer entered by user
in variable num1 and num2 */
sum=num1+num2; /* Performs addition and stores it in variable sum
*/
printf("Sum: %d",sum); /* Displays sum */
return 0;
}
Output
Enter two integers: 12
11
Sum: 23
Explanation
In this program, user is asked to enter two integers. The two integers entered by user
will be stored in variables num1 and num2 respectively. This is done using scanf(
) function. Then, + operator is used for adding variables num1 and num2 and this value is
assigned to variable sum.
Finally, the sum is displayed and program is terminated.

There are three variables used for performing this task but, you can perform this same
task using 2 variables only. It can done by assiging the sum of num1 and num2 to one of
these variables as shown in figure below.
/* C programming source code to add and display the sum of two integers
entered by user using two variables only. */
#include <stdio.h>
int main( )
{
int num1, num2, sum;
printf("Enter a two integers: ");
scanf("%d %d",&num1,&num2);
num1=num1+num2; /* Adds variables num1 and num2 and stores it in num1
*/
printf("Sum: %d",num1); /* Displays value of num1 */
return 0;
}
This source code calculates the sum of two integers and displays it but, this program
uses only two variables.
C Program to Multiply two Floating Point Numbers
In this program, user is asked to enter two floating point numbers and this program will mulitply
these two numbers and display it.
/*C program to multiply and display the product of two floating point
numbers entered by user. */
#include <stdio.h>
int main( )
{
float num1, num2, product;

printf("Enter two numbers: ");
scanf("%f %f",&num1,&num2); /* Stores the two floating point
numbers entered by user in variable num1 and num2 respectively */
product = num1*num2; /* Performs multiplication and stores it */
printf("Product: %f",product);
return 0;
}
Output
Enter two numbers: 2.4
1.1
Product: 2.640000
Explanation
In this program, user is asked to enter two floating point numbers. These two numbers entered
by user will be stored in variables num1 and num2 respectively. This is done using scanf(
) function. Then, * operator is used for multiplying variables and this value is stored in
variable product.
Then, the product is displayed and program is terminated.
C Program to Find ASCII Value of a Character
Every character in C programming is given an integer value to represent it. That integer value is
known as ASCII value of that character. For example: ASCII value of 'a' is 97. Here is the
complete list of ASCII value of characters in C programming. When a character is stored in
variable of typechar, the ASCII value of character is stored instead of that character itself
character itself. For example: If you try to store character 'a' in a char type variable, ASCII value
of that character is stored which is 97.
In, this program user is asked to enter a character and this program will display the ASCII value
of that character.

Source Code
/* Source code to find ASCII value of a character entered by user */
#include <stdio.h>
int main(){
char c;
printf("Enter a character: ");
scanf("%c",&c); /* Takes a character from user */
printf("ASCII value of %c = %d",c,c);
return 0;
}
Output
Enter a character: G
ASCII value of G = 71
Explanation
In this program, user is asked to enter a character and this character will be stored in variable c,
i.e., the ASCII value of that character is stored in variable c. When, this value is displayed
usingconversion format string %c , the actual variable is displayed but, when this variable is
displayed using format string %d, the ASCII value of that character is displayed.
C Program to Find Quotient and Remainder of Two Integers
Entered by User
In this program, user is asked to enter two integers(dividend and divisor) and this program will
compute the quotient and remainder and display it.
/* C Program to compute remainder and quotient */
#include <stdio.h>
int main(){
int dividend, divisor, quotient, remainder;
printf("Enter dividend: ");
scanf("%d",&dividend);
printf("Enter divisor: ");
scanf("%d",&divisor);
quotient=dividend/divisor; /* Computes quotient */
remainder=dividend%divisor; /* Computes remainder */
printf("Quotient = %dn",quotient);
printf("Remainder = %d",remainder);

return 0;
}
Output
Enter dividend: 25
Enter divisor: 4
Quotient = 6
Remainder = 1
Explanation
This program takes two integers(dividend and divisor) from user and stores it in
variable dividendand divisor. Then, quotient and remainder is calculated and stored in
variable quotient andremainder. Operator / is used for calculation of quotient and % is used
for calculating remainder. Learn more about divison(/) and modulo division(%) operator in C
programming
You can also program can be performed using only two variables as:
/* C Program to compute and display remainder and quotient using only two
variables */
#include <stdio.h>
int main(){
int dividend, divisor;
printf("Enter dividend: ");
scanf("%d",&dividend);
printf("Enter divisor: ");
scanf("%d",&divisor);
printf("Quotient = %dn",dividend/divisor);/* Computes and displays quotient
*/
printf("Remainder = %d",dividend%divisor); /* Computes and displays remainder
*/
return 0;
}
Output of this program is same as program above but, only two variables are used in this case
instead of four variables.

C Program to Find Size of int, float, double and char of Your
System
The size of a character is always 1 byte but, size of int, float and double variables differs from
system to system. This program will compute the size of int, float, double a nd char of you
system using sizeof operator. The syntax of size of operator is:
temp = sizeof(operand);
/* Here, temp is a variable of type integer,i.e, sizeof() operator
returns integer value. */
Source Code
/* This program computes the size of variable using sizeof operator.*/
#include <stdio.h>
int main(){
int a;
float b;
double c;
char d;
printf("Size of int: %d bytesn",sizeof(a));
printf("Size of float: %d bytesn",sizeof(b));
printf("Size of double: %d bytesn",sizeof(c));
printf("Size of char: %d byten",sizeof(d));
return 0;
}
Output
Size of int: 4 bytes
Size of float: 4 bytes
Size of double: 8 bytes
Size of char: 1 byte
Note: You may get different output depending upon your system.
Explanation
In this program, 4 variables a, b, c and d are declared of type int, float, double and char
respectively. Then, the size of these variables is computed using sizeof operator and displayed.
C Program to Demonstrate the Working of Keyword long
Keyword long is used for altering the size of data type. For example: the size of int is either 2
bytes or 4 bytes but, when long keyword is used, the size of long int will be either 4 bytes or 8

bytes. Also, you can use long long int. The size of long long int is generally 8 bytes.
This program will demonstrate the size of keyword long for my system. It may be different in
your system.
Source Code
#include <stdio.h>
int main(){
int a;
long int b; /* int is optional. */
long long int c; /* int is optional. */
printf("Size of int = %d bytesn",sizeof(a));
printf("Size of long int = %ld bytesn",sizeof(b));
printf("Size of long long int = %ld bytes",sizeof(c));
return 0;
}
Output
Size of int = 4 bytes
Size of long int = 4 bytes
Size of long long int = 8 bytes
In this program, the sizeof operator is used for finding the size of int, long int and long
long int.
Thus, int and long int for my system can hold values from -231
to 23 1
-1. If I have to work on
data outside this range, I have to use long long int, which can hold values from -26 3
to 26 3
-1 .
Similarly, the long keyword can be used double and floats types.
C Program to Swap Two Numbers
This program asks user to enter two numbers and this program will swap the value of these two
numbers.
#include <stdio.h>
int main(){
float a, b, temp;
printf("Enter value of a: ");
scanf("%f",&a);
printf("Enter value of b: ");
scanf("%f",&b);
temp = a; /* Value of a is stored in variable temp */

a = b; /* Value of b is stored in variable a */
b = temp; /* Value of temp(which contains initial value of a) is
stored in variable b*/
printf("nAfter swapping, value of a = %.2fn", a);
printf("After swapping, value of b = %.2f", b);
return 0;
}
Output
Enter value of a: 1.20
Enter value of b: 2.45
After swapping, value of a = 2.45
After swapping, value of b = 1.2
C Programming Enumeration
An enumeration is a user-defined data type consists of integral constants and each integral
constant is give a name. Keyword enum is used to defined enumerated data type.
enum type_name{ value1, value2,...,valueN };
Here, type_name is the name of enumerated data type or tag.
And value1, value2,....,valueN are values of type type_name.
By default, value1 will be equal to 0, value2 will be 1 and so on but, the programmer can
change the default value as below:
enum suit{
club=0;
diamonds=10;
hearts=20;
spades=3;
};
Declaration of enumerated variable
Above code defines the type of the data but, no any variable is created. Variable of
type enum can be created as:
enum boolean{
false;
true;

};
enum boolean check;
Here, a variable check is declared which is of type enum boolean.
Example of enumerated type
#include <stdio.h>
enum week{ sunday, monday, tuesday, wednesday, thursday, friday,
saturday};
int main(){
enum week today;
today=wednesday;
printf("%d day",today+1);
return 0;
}
Output
4 day
You can write any program in C language without the help of enumerations but, enumerations
helps in writing clear codes and simplify programming.

Example 1: C if statement
Write a C program to print the number entered by user only if the number entered is
negative.
#include <stdio.h>
int main(){
int num;
printf("Enter a number to check.n");
scanf("%d",&num);
if(num<0) { /* checking whether number is less than 0 or not.
*/
printf("Number = %dn",num);
}
/*If test condition is true, statement above will be executed, otherwise
it will not be executed */
printf("The if statement in C programming is easy.");
return 0;
}
Output 1
Enter a number to check.
-2
Number = -2
The if statement in C programming is easy.
When user enters -2 then, the test expression (num<0) becomes true. Hence, Number =
-2 is displayed in the screen.
Output 2
Enter a number to check.
5
The if statement in C programming is easy.
When the user enters 5 then, the test expression (num<0) becomes false. So, the
statement/s inside body of if is skipped and only the statement below it is executed.
C if...else statement
The if...else statement is used if the programmer wants to execute some statement/s
when the test expression is true and execute some other statement/s if the test
expression is false.
Syntax of if...else
if (test expression) {

statements to be executed if test expression is true;
}
else {
statements to be executed if test expression is false;
}
Flowchart of if...else statement
Example 2: C if...else statement
Write a C program to check whether a number entered by user is even or odd
#include <stdio.h>
int main(){
int num;
printf("Enter a number you want to check.n");
scanf("%d",&num);
if((num%2)==0) //checking whether remainder is 0 or not.
printf("%d is even.",num);
else
printf("%d is odd.",num);

return 0;
}
Output 1
Enter a number you want to check.
25
25 is odd.
Output 2
Enter a number you want to check.
2
2 is even.
Nested if...else statement (if...elseif....else
Statement)
The nested if...else statement is used when program requires more than one test
expression.
Syntax of nested if...else statement.
if (test expression1){
statement/s to be executed if test expression1 is true;
}
else if(test expression2) {
statement/s to be executed if test expression1 is false and 2 is true;
}
else if (test expression 3) {
statement/s to be executed if text expression1 and 2 are false and 3 is
true;
}
.
.
.
else {
statements to be executed if all test expressions are false;
}
How nested if...else work s?
The nested if...else statement has more than one test expression. If the first test
expression is true, it executes the code inside the braces{ } just below it. But if the first
test expression is false, it checks the second test expression. If the second test
expression is true, it executes the statement/s inside the braces{ } just below it. This

process continues. If all the test expression are false, code/s inside else is executed
and the control of program jumps below the nested if...else
The ANSI standard specifies that 15 levels of nesting may be continued.
Example 3: C nested if else statement
Write a C program to relate two integers entered by user using = or > or < sign.
#include <stdio.h>
int main(){
int numb1, numb2;
printf("Enter two integers to checkn");
scanf("%d %d",&numb1,&numb2);
if(numb1==numb2) //checking whether two integers are equal.
printf("Result: %d = %d",numb1,numb2);
else
if(numb1>numb2) //checking whether numb1 is greater than numb2.
printf("Result: %d > %d",numb1,numb2);
else
printf("Result: %d > %d",numb2,numb1);
return 0;
}
Output 1
Enter two integers to check.
5
3
Result: 5 > 3
Output 2
Enter two integers to check.
-4
-4
Result: -4 = -4

C Programming Loops
Loops cause program to execute the certain block of code repeatedly until test condition
is false. Loops are used in performing repetitive task in programming. Consider these
scenarios:
 You want to execute some code/s 100 times.
 You want to execute some code/s certain number of times depending upon input from user.
These types of task can be solved in programming using loops.
There are 3 types of loops in C programming:
1. for loop
2. while loop
3. do...while loop
for Loop Syntax
for(initialization statement; test expression; update statement) {
code/s to be executed;
}
How for loop works in C programming?
The initialization statement is executed only once at the beginning of the for loop. Then
the test expression is checked by the program. If the test expression is false, for loop is
terminated. But if test expression is true then the code/s inside body of for loop is
executed and then update expression is updated. This process r epeats until test
expression is false.
This flowchart describes the working of for loop in C programming.

for loop example
Write a program to find the sum of first n natural numbers where n is entered by user.
Note: 1,2,3... are called natural numbers.
#include <stdio.h>
int main(){
int n, count, sum=0;
printf("Enter the value of n.n");
scanf("%d",&n);
for(count=1;count<=n;++count) //for loop terminates if count>n
{
sum+=count; /* this statement is equivalent to
sum=sum+count */
}
printf("Sum=%d",sum);
return 0;

}
Output
Enter the value of n.
19
Sum=190
In this program, the user is asked to enter the value of n. Suppose you entered 19 then,
count is initialized to 1 at first. Then, the test expression in the for loop,i.e., (count<=
n) becomes true. So, the code in the body of for loop is executed which makes sum to 1.
Then, the expression ++count is executed and again the test expression is checked,
which becomes true. Again, the body of for loop is executed which makes sum to 3 and
this process continues. When count is 20, the test condition becomes false and the for
loop is terminated.
Syntax of while loop
while (test expression) {
statement/s to be executed.
}
The while loop checks whether the test expression is true or not. If it is true, code/s
inside the body of while loop is executed,that is, code/s inside the braces { } are
executed. Then again the test expression is checked whether test expression is true or
not. This process continues until the test expression becomes false.
Example of while loop
Write a C program to find the factorial of a number, where the number is entered by user.
(Hints: factorial of n = 1*2*3*...*n

/*C program to demonstrate the working of while loop*/
#include <stdio.h>
int main(){
int number,factorial;
printf("Enter a number.n");
scanf("%d",&number);
factorial=1;
while (number>0){ /* while loop continues util test condition
number>0 is true */
factorial=factorial*number;
--number;
}
printf("Factorial=%d",factorial);
return 0;
}
Output
Enter a number.
5
Factorial=120
do...while loop
In C, do...while loop is very similar to while loop. Only difference between these two
loops is that, in while loops, test expression is checked at first but, in do...while loop
code is executed at first then the condition is checked. So, the code are executed at
least once in do...while loops.
Syntax of do...while loops
do {
some code/s;
}
while (test expression);
At first codes inside body of do is executed. Then, the test expression is checked. If it is
true, code/s inside body of do are executed again and the process continues until test
expression becomes false(zero).
Notice, there is semicolon in the end of while (); in do...while loop.

Example of do...while loop
Write a C program to add all the numbers entered by a user until user enters 0.
/*C program to demonstrate the working of do...while statement*/
#include <stdio.h>
int main(){
int sum=0,num;
do /* Codes inside the body of do...while loops are at
least executed once. */
{
scanf("%d",&num);
sum+=num;
}
while(num!=0);
printf("sum=%d",sum);
return 0;
}
Output
Enter a number
3
Enter a number
-2
Enter a number
0
sum=1
In this C program, user is asked a number and it is added with sum. Then, only the test
condition in the do...while loop is checked. If the test condition is true,i.e, num is not
equal to 0, the body of do...while loop is again executed until num equals to zero.

break Statement
In C programming, break is used in terminating the loop immediately after it is
encountered. The break statement is used with conditional if statement.
Syntax of break statement
break;
The break statement can be used in terminating all three loops for, while and do...while
loops.
The figure below explains the working of break statement in all three type of loops.

Example of break statement
Write a C program to find average of maximum of n positive numbers entered by user. But,
if the input is negative, display the average(excluding the average of negative input) and
end the program.
/* C program to demonstrate the working of break statement by terminating
a loop, if user inputs negative number*/
# include <stdio.h>
int main(){
float num,average,sum;
int i,n;
printf("Maximum no. of inputsn");
scanf("%d",&n);
for(i=1;i<=n;++i){
printf("Enter n%d: ",i);
scanf("%f",&num);
if(num<0.0)
break; //for loop breaks if num<0.0
sum=sum+num;
}
average=sum/(i-1);

printf("Average=%.2f",average);
return 0;
}
Output
Maximum no. of inputs
4
Enter n1: 1.5
Enter n2: 12.5
Enter n3: 7.2
Enter n4: -1
Average=7.07
In this program, when the user inputs number less than zero, the loop is terminated
using break statement with executing the statement below it i.e., without
executing sum=sum+num.
In C, break statements are also used in switch...case statement. You will study it in C
switch...case statement chapter.
continue Statement
It is sometimes desirable to skip some statements inside the loop. In such cases,
continue statements are used.
Syntax of continue Statement
continue;
Just like break, continue is also used with conditional if statement.

For better understanding of how continue statements works in C programming. Analyze
the figure below which bypasses some code/s inside loops using continue statement.
Example of continue statement
Write a C program to find the product of 4 integers entered by a user. If user enters 0 skip
it.
//program to demonstrate the working of continue statement in C
programming
# include <stdio.h>
int main(){
int i,num,product;
for(i=1,product=1;i<=4;++i){
printf("Enter num%d:",i);
scanf("%d",&num);
if(num==0)
continue; / *In this program, when num equals to zero, it
skips the statement product*=num and continue the loop. */
product*=num;
}
printf("product=%d",product);
return 0;

}
Output
Enter num1:3
Enter num2:0
Enter num3:-5
Enter num4:2
product=-30
C Programming goto Statement
In C programming, goto statement is used for altering the normal sequence of program execution
by transferring control to some other part of the program.
Syntax of goto statement
goto label;
.............
.............
.............
label:
statement;
In this syntax, label is an identifier. When, the control of program reaches to goto statement, the
control of the program will jump to the label: and executes the code below it.
Example of goto statement
/* C program to demonstrate the working of goto statement. */
/* This program calculates the average of numbers entered by user. */
/* If user enters negative number, it ignores that number and
calculates the average of number entered before it.*/

# include <stdio.h>
int main(){
float num,average,sum;
int i,n;
printf("Maximum no. of inputs: ");
scanf("%d",&n);
for(i=1;i<=n;++i){
printf("Enter n%d: ",i);
scanf("%f",&num);
if(num<0.0)
goto jump; /* control of the program moves to label
jump */
sum=sum+num;
}
jump:
average=sum/(i-1);
printf("Average: %.2f",average);
return 0;
}
Output
Maximum no. of inputs: 4
Enter n1: 1.5
Enter n2: 12.5
Enter n3: 7.2
Enter n4: -1
Average: 7.07
Though goto statement is included in ANSI standard of C, use of goto statement should be
reduced as much as possible in a program.
Reasons to avoid goto statement
Though, using goto statement give power to jump to any part of program, using goto statement
makes the logic of the program complex and tangled. In modern programming, goto statement is
considered a harmful construct and a bad programming practice.
The goto statement can be replaced in most of C program with the use of break and continue
statements. In fact, any program in C programming can be perfectly written without the use of
goto statement. All programmer should try to avoid goto statement as possible as they can.

C Programming switch Statement
Decision making are needed when, the program encounters the situation to choose a particular
statement among many statements. If a programmer has to choose one block of statement among
many alternatives, nested if...else can be used but, this makes programming logic complex. This
type of problem can be handled in C programming using switch statement.
Syntax of switch...case
switch (n) {
case constant1:
code/s to be executed if n equals to constant1;
break;
case constant2:
code/s to be executed if n equals to constant2;
break;
.
.
.
default:
code/s to be executed if n doesn't match to any cases;
}
The value of n is either an integer or a character in above syntax. If the value of n matches
constant in case, the relevant codes are executed and control moves out of
the switch statement. If the ndoesn't matches any of the constant in case, then the default codes
are executed and control moves out of switch statement.

Example of switch...case statement
Write a program that asks user an arithmetic operator('+','-','*' or '/') and two operands
and perform the corresponding calculation on the operands.
/* C program to demonstrate the working of switch...case statement */
/* C Program to create a simple calculator for addition, subtraction,
multiplication and division */
# include <stdio.h>
int main() {
char o;
float num1,num2;
printf("Select an operator either + or - or * or / n");
scanf("%c",&o);
printf("Enter two operands: ");
scanf("%f%f",&num1,&num2);
switch(o) {
case '+':
printf("%.1f + %.1f = %.1f",num1, num2, num1+num2);
break;
case '-':

printf("%.1f - %.1f = %.1f",num1, num2, num1-num2);
break;
case '*':
printf("%.1f * %.1f = %.1f",num1, num2, num1*num2);
break;
case '/':
printf("%.1f / %.1f = %.1f",num1, num2, num1/num2);
break;
default:
/* If operator is other than +, -, * or /, error message is
shown */
printf("Error! operator is not correct");
break;
}
return 0;
}
Output
Enter operator either + or - or * or /
*
Enter two operands: 2.3
4.5
2.3 * 4.5 = 10.3
The break statement at the end of each case cause switch statement to exit. If break statement
is not used, all statements below that case statement are also executed.

C Programming

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