Principles of Programming using C (BPOPS103/203) Module 2

MODULE 2

Operators in C, Type conversion and typecasting

Decision control and Looping statements: Introduction to decision control, Conditional branching
statements, iterative statements, nested loops, break and continue statements, goto statement.

Textbook: Chapter 9.15-9.16, 10.1-10.6

Chapter 2: Decision control and looping statements:

 A Statement causes an action to be performed.
 A statement is a group of tokens ended with a semicolon.
 A C program is a set of statements which are normally executed sequentially in the order in which
they appear.
 However, in practice there are number of situations where we may have to change the order of
execution of statements based on conditions, or repeat a group of statements until certain specified
conditions are met.
So C, possesses decision making capabilities – These statements are popularly known as decision making
statements. Also known as control statements or as control structures.
Categories of control structures:
Decision making and branching (conditional statements) – specifies a condition to execute
one or more statements in a program. (if, switch, conditional operator)
Decision making and branching (Unconditional statements) – changes the normal sequence
of the program execution by transferring control to other part of the program (goto, continue,
break)
Decision making and Looping (Iterative statements) – executes one or more statements
repeatedly until some condition is met. (while, do while, for)
Conditional branching statements
C language possesses such decision making capabilities and branching (conditional statements) by
supporting the following statements
1. if statement
2. switch statement
3. Conditional operator statement

DECISION MAKING WITH IF STATEMENT

The if statement is a two way decision statement.

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It allows the computer to evaluate the expression first and then, depending on whether the value of the
expression (relation or condition) is ‘true’ (non zero) or ‘false’ (zero), it transfers the control to a particular
statement. This point of program has two paths to follow, one for the true condition and the other for the
false condition.
The if statement may be implemented in different forms depending on the complexity of conditions to be
tested. They are:
1. Simple if statement
2. If….else statement
3. Nested if …..else statement
4. if else if ladder

SIMPLE IF STATEMENT
The general form of a simple if statement is:
if (test expression)
{
Statement-block;
}
Statement-x;
The ‘statement-block’ may be a single statement or a group of statements. If the test expression is true, the
statement-block will be executed; otherwise the statement-block will be skipped and the execution will
jump to the statement-x. When condition is true both the statement-block and statement-x are executed in
sequence.

Program: eligible to vote or not

#include<stdio.h>

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int main()
{
int age;
printf("\n Enter age ");
scanf("%d ", &age);
if(age>=18)
printf(“\n Eligible to vote”);
if(age<18)
printf(“\n Not eligible to vote”);
return 0;
}
In case the statement block contains only one statement, putting curly brackets becomes optional. If there is
more than one statement in the statement block, putting curly brackets becomes mandatory.
THE IF….ELSE STATEMENT
The if…..else statement is an extension of the simple if statement. The general form is:
if (test expression)
{
true-block statement(s);
}
else
{
false-block statement(s);
}
Statement-x;
If the test expression is true, then the true-block statement(s), immediately following the if statement are
executed; otherwise, the false-block statement(s), are executed. In either case true-block or false-block will
be executed, not both.

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True False

Test
express
ion?

False-block
True-block
statement
statement

Statement-x

Fig: Flowchart
Program: greatest of two numbers
#include<stdio.h>
int main()
{
int a, b;
printf("\n Enter two integer values");
scanf("%d %d ", &a, &b);
if(a>b)
printf(“%d is greatest”,a);
else
printf(“%d is greatest”,b);
return 0;
}
Program: odd or even
#include<stdio.h>
int main()
{
int a;
printf("Enter a value ");

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scanf("%d ", &a);

if(a%2==0)
{
printf(“%d is even”,a);
}
else
{
printf(“%d is odd”,a);
}
return 0;
}
Program: eligible to vote or not
int main()
{
int age;
printf("Enter age ");
scanf("%d ", &age);
if(age>=18)
printf(“eligible to vote”);
else
printf(“not eligible to vote”);
return 0;
}
Program: vowel or not
#include<stdio.h>
#include<ctype.h>
int main()
{
char c;
printf("Enter a valid character ");
scanf("%c", &c);
c=tolower(c);
if(c==’a’||c==’e’||c==’i’||c==’o’||c==’u’)

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printf(“Input character is a vowel”);

else
printf(“Input character is a consonant”);
return 0;
}
Program: leap year or not
#include<stdio.h>
int main()
{
int year;
printf("Enter a valid year ");
scanf("%d", &year);
if((year%4==0&&year%100!=0)|| year%400==0)
printf(“Input year is a leap year”);
else
printf(“Input year is not a leap year”);
return 0;
}
NESTING OF IF…ELSE STATEMENTS
When a series of decisions are involved, we may have to use more than one if…else statements in nested
form as shown below
If the condition-1 is false, the statement-3 will be executed; otherwise it continues to perform the second
test. if the condition-2 is true the statement-1 will be evaluated; otherwise the statement-2 will be evaluated
and then the control is transferred to the statement-x.
Syntax: Fig: Flowchart

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Program
#include<stdio.h>
int main()
{
float a,b,c;
printf("Enter three values\n");
scanf("%f %f %f", &a, &b, &c);
if (a>b)
{
if (a>c)
printf("\n %f is largest", a);
else
printf("%f is largest ", c);
}
else
{
Output
if (c>b)
Enter three values
printf("%f is largest ",c);
23445 67379 88843
else
Largest value is 88843.000000
printf("%f is largest ", b);
}

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return 0;
}
DANGLING ELSE PROBLEM
One of the classic problems encountered when we start using nested if….else statement is the
dangling else. This occurs when a matching else is not available for an if. The answer to this problem is
very simple.
Always match an else to the most recent unmatched if in the current block. In some cases, it is
possible that the false condition is not required. In such situations, else statement may be omitted. (else is
always paired with recent unpaired if in the current block)
if(n>0)
if(a>b)
z=a;
else
z=b;
The else is associated with if(a>b). If we want else to be associated with if (n>0), then brackets should be
used like this:
if(n>0)
{
if(a>b)
z=a;
}
else
z=b;
THE ELSE IF LADDER
Nested if else is difficult to understand and modify. So we use else if ladder. Also called cascaded if else.
There is another way of putting ifs together when multipath decision are involved. A multipath decision is a
chain of ifs in which the statement associated with each else is an if. This construct is known as the else if
ladder.
Syntax: Fig:Flowchart

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Program (greatest of three numbers)

#include<stdio.h>
int main()
{
float a, b, c;
printf("Enter three values\n");
scanf("%f %f %f", &a, &b, &b);
if(a>b && a>c)
printf("%f is greatest", a);
else if(b>c)
printf("%f is greatest", b);
else
printf("%f is greatest", c);
return 0;
}

Program (zero, positive or negative)

#include<stdio.h>
int main()
{
int a;

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printf("Enter a value");
scanf("%d", &a);
if(a==0)
printf("%d is zero", a);
else if(a>0)
printf("%d is positive", a);
else
printf("%d is negative", a);
return 0;
}

Program (vowel or consonant)

#include<stdio.h>
int main()
{
char a;
printf("Enter a character");
scanf("%c", &a);
a=tolower(a);
if(a==’a’)
printf("%c is a vowel", a);
else if(a==’e’)
printf("%c is a vowel", a);
else if(a==’i’)
printf("%c is a vowel", a);
else if(a==’o’)
printf("%c is a vowel", a);
else if(a==’u’)
printf("%c is a vowel", a);
else
printf("%c is not a vowel or it is a consonant", a);
return 0;
}
Program:

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Consider the following as grading of academic institution: Find the grade of a student if marks is given as
input.
Average marks Grade
80-100 Honours
60-79 First division
50-59 Second division
40-49 Third division
0-39 Fail
#include<stdio.h>
int main()
{
int marks;
printf("Enter the marks of a student");
scanf("%d", &marks);
if(marks>=80)
printf(“honours");
else if(marks>=60)
printf(“First division");
else if(marks>=50)
printf(“Second division");
else if(marks>=40)
printf(Third division");
else
printf(“Fail");
return 0;
}
Program - Compute the roots of a quadratic equation by accepting the coefficients. Print appropriate
messages.
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main()
{
float a,b,c, d,root1,root2,real,imag;
printf("Enter the three coefficients:\n");
scanf("%f%f%f",&a,&b,&c);

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if(a==0)
{
printf("Invalid coefficients");
exit(0);
}
d=b*b-4*a*c;
if(d>0)
{
root1=(-b+(sqrt(d)))/(2.0*a);
root2=(-b-(sqrt(d)))/(2.0*a);
printf("The roots are real and distinct....\n");
printf("root1=%f \n root2=%f\n",root1,root2);
}
else if(d==0)
{
root1=root2=-b/(2.0*a);
printf("The roots are real and equal....\n");
printf("root1=%f \n root2=%f\n",root1,root2);
}
else
{
real=-b/(2.0*a);
imag= sqrt(fabs(d))/(2.0*a);
printf("The roots are complex and imaginary....\n");
printf("root1=%f+i %f \n root2= %f-i%f",real,imag,real,imag);
}
return 0;
}
Program - An electricity board charges the following rates for the use of electricity: for the first 200
units 80 paise per unit: for the next 100 units 90 paise per unit: beyond 300 units Rs 1 per unit. All
users are charged a minimum of Rs. 100 as meter charge. If the total amount is more than Rs 400,
then an additional surcharge of 15% of total amount is charged. Write a program to read the name of
the user, number of units consumed and print out the charges.
#include<stdio.h>
int main()
{
char name[20];
int units;
float charges=0;
printf("\n enter the name of the user :");
gets(name);
printf("\n enter number of units consumed :");
scanf("%d",&units);
if(units<=200)
{
charges=units*0.80;
}
else if(units<=300 && units>200)
{
charges=200*0.80+(units-200)*0.90;

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}
else
{
charges=200*0.80+100*0.90+(units-300)*1.00;
}
charges=charges+100;
if(charges>400)
charges=charges+0.15*charges;
printf("%s has to pay rupees %f",name,charges);
return 0;
}
THE SWITCH STATEMENT
C has a built-in multi-way decision statement known as a switch. The switch statement tests the
value of a given variable (or expression) against a list of case values and when a match is found, a block of
statement associated with that case is executed.
The general form of the switch statement is as shown below
switch (expression)
{
case value-1:
Statement Block-1;
break;
case value-2:
Statement Block-2;
break;
……..
………
default:
default-block;
break;
}
Statement-x;
The expression evaluates to an integral value (ie) an integer or character value. Value-1, Value-2….are
constants known as case labels. Each of these values should be unique within a switch statement. Statement
block-1, block-2…are statement list and may contain zero or more statements. There is no need to put
braces around these blocks. case has labels end with a colon (:)
When the switch is executed ,the value of the expression is successfully compared against the values
value-1,value-2… if a case is found whose value matches with the value of the expression, then the block of

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statements that follows the case are executed.

The default is an optional case. When present, it will be executed if the value of the expression does not
match with any of the case values. If not present, no action takes place if all matches fail and the control
goes to the statement-x. break keyword indicates case is ended and control moves out of switch.
The selection process of switch statement is illustrated in the flow chart shown

Fig: Flowchart
Advantages of Using a switch case Statement
Switch case statement is preferred by programmers due to the following reasons:
 Easy to debug
 Easy to read and understand
 Ease of maintenance as compared with its equivalent if-else statements
 Like if-else statements, switch statements can also be nested
 Executes faster than its equivalent if-else construct

Program:
Consider the following as grading of academic institution: Find the grade of a student if marks is given as
input.
Average marks Grade
80-100 Honours
60-79 First division
50-59 Second division
40-49 Third division
0-39 Fail
The switch statement can be used to grade the students.
#include<stdio.h>
int main()

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{
int marks,index;
printf("Enter the marks of a student");
scanf("%d", &marks);
index=marks/10;
switch (index)
{
case 10:
case 9:
case 8:
printf( “\n Honours”);
break;
case 7:
Case 6:
printf( “\n First Division”);
break;
case 5:
printf( “\n Second Division”);
break;
case 4:
printf( “\n Third Division”);
break;
default:
printf( “\n Fail”);
}
return 0;
}
Program: Simulation of a Simple Calculator.
#include<stdio.h>
#include<stdlib.h>
int main()
{
int a,b,res;

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char op;
printf("\n Enter a simple arithmetic expression");
scanf("%d%c%d",&a,&op,&b);
switch(op)
{
case '+':
res=a+b;
break;
case '-':
res=a-b;
break;
case '*':
res=a*b;
break;
case '/':
if(b!=0)
res=a/b;
else
{
printf("division by zero is not possible");
exit(0);
}
break;
case '%':
res=a%b;
break;
default:
printf("illegal operator");
exit(0);
}
printf("\n%d%c%d=%d",a,op,b,res);
return 0;
}

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Program (vowel or consonant)

#include<stdio.h>
#include<ctype.h>
int main()
{
char a;
printf("Enter a character");
scanf("%c", &a);
a=tolower(a);
switch(a)
{
case ‘a’:
case ‘e’:
case ‘i’:
case ‘o’:
case ‘u’:
printf("%c is a vowel", a);
break;
default:
printf("%c is not a vowel or consonant", a);
}
return 0;
}
THE ? : OPERATOR (The Ternary Operator)
The C language has an unusual operator, useful for making two-way decisions. This operator is a
combination of ? and : and takes three operands. This operator is popularly known as the conditional
operator.
Syntax: conditional expression? expression1:expression2

The conditional expression is evaluated first. If the result is non zero, expression1 is evaluated and is
returned as the value of the condition expression. Otherwise, expression2 is evaluated and its value is
returned. For example, the segment
if(a>b)

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big=a;
else
big=b;
Can be written as
big=(a>b) ? a : b;
Conditional operator can be nested for evaluating complex conditions.
Advantages: When the conditional operator is used, the code becomes more concise and perhaps, more
efficient.
Disadvantages: readability is poor.
Program: Smallest of two numbers
#include<stdio.h>
int main()
{
int a,b,small;
printf("enter two numbers");
scanf("%d%d",&a,&b);
small=(a<b)?a:b;
printf("%d is smallest",small);
return 0;
}
Program: Smallest of three numbers
#include<stdio.h>
int main()
{
int a,b,c,small;
printf("enter three numbers");
scanf("%d%d%d",&a,&b,&c);
small=(a<b&&a<c)?a:(b<c?b:c);
printf("%d is smallest",small);
return 0;
}
Decision making and Looping (Iterative statements) – executes one or more statements repeatedly until
some condition is met. (while, do while, for)

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A program loop therefore consists of two segments,

1. body of the loop – statements to be repeatedly executed.
2. control statement – specifies a test condition to perform the body of loop.

Depending on the position of the control statement in the loop, a control structure may be classified either
as the entry-controlled loop or as the exit-controlled loop.
In the entry controlled loop, the control conditions are tested before the start of the loop execution. If the
conditions are not satisfied, and then the body of the loop will not be executed.
In the case of an exit-controlled loop, the test is performed at the end of the body of the loop and therefore
the body is executed unconditionally for the first time. The entry-controlled loops and exit controlled loops
also known as pre-test and post-test loops respectively.
Entry-controlled loop Exit- controlled loop
Control conditions are tested before the body Control conditions are tested after the body of
of the loop the loop
If the control condition is false for the first Body of the loop is executed at least one time
time, body of the loop is never executed irrespective of the condition
It is called pre-test loop It is called post-test loop
Example – while, for Example – do while
Flow-chart shown below Flow-chart shown below

Loops enter to infinite loop, if the condition does not fail.

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A looping process would include the following four steps:

1. Setting and initialization of a condition variable or control variable.
2. Execution of statements in the loop (body of the loop).
3. Test for a specified value of the control variable for execution of the loop.
4. Incrementing or updating the condition variable.

The C language provides for three constructs for performing loop operations
1. The while statement
2. The do while statement
3. The for statement

THE WHILE STATEMENT

The simplest of all the looping structures in C is the while statement. The while is an entry-controlled loop
statement.
Syntax: while (test condition)
{
body of the loop;
}
The test-condition is evaluated and if the condition is true, then the body of the loop is executed. After
execution of the body, the test-condition is once again evaluated and if it is true, the body is executed once
again. This process of repeated execution of the body continues until the test-condition finally becomes
false and the control is transferred out of the loop. On exit, the program continues with the statement
immediately after the body of the loop.

Program (print first n natural numbers)

#include<stdio.h>
int main()

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{
int i,n;
printf(“enter n:”);
scanf(“%d”,&n);
i=1;
while(i<=n)
{
printf(“%d\t”,i);
i++;
}
return 0;
}
Program (print first n natural numbers in reverse)
#include<stdio.h>
int main()
{
int i,n;
printf(“enter n:”);
scanf(“%d”,&n);
i=n;
while(i>=1)
{
printf(“%d\t”,i);
i--;
}
return 0;
}
Program (print the sum of first n numbers)
#include<stdio.h>
int main()
{
int i,n,sum=0;
printf(“enter n:”);

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scanf(“%d”,&n);
i=1;
while(i<=n)
{
sum=sum+i;
i=i+1;
}
printf(“sum=%d”,sum);
return 0;
}
Program (print the sum of first n squares)
#include<stdio.h>
void main()
{
int i,n,sum=0;
printf(“enter n:”);
scanf(“%d”,&n);
i=1;
while(i<=n)
{
sum=sum+i*i;
i=i+1;
}
printf(“sum=%d”,sum);
}
THE do while LOOPING STATEMENT
On some, occasions it might be necessary to execute to the body of the loop before the test is performed.
Such situations can be handled with the help of the do statement.
Syntax:
do
{
body of the loop;
}

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while(test-condition);

Since the test-condition is evaluated at the bottom of the loop, the do…while is an exit-controlled loop.
Program (print first n natural numbers)
#include<stdio.h>
int main()
{
int i,n;
printf(“enter n:”);
scanf(“%d”,&n);
i=1;
do
{
printf(“%d\t”,i);
i++;
}
while(i<=n);
return 0;
}
THE FOR STATEMENT
Simple ‘for' Loops
The for loop is another entry-controlled loop that provides a more concise loop control structure.
The general form of the for loop is
Syntax:

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for(initialization; test-condition ; increment)

{
body of the loop;
}

The execution of the for statement is as follows

1. Initialization of the control variables is done first.
2. The value of the control variable is tested using the test-condition. If the condition is true, the body of the
loop is executed; otherwise the loop is terminated and the execution continues with the statement that
immediately follows the loop.
3. When the body at the loop is executed, the control is transferred back to the for statement
after evaluating the last statement in the loop. Now, the control variable is Incremented using an assignment
statement such as i=i+1 and the new value of the control variable is again tested to see whether it satisfies
the loop condition. If the condition is satisfied, the body of the loop is again executed. This process
continues till the value of the control variable fails to satisfy the test-condition.
Program (print first n natural numbers)
#include<stdio.h>
int main()
{
int i,n;
printf(“enter n:”);

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scanf(“%d”,&n);
for(i=1;i<=n;i++)
{
printf(“%d\t”,i);
}
return 0;
}
Program (print even numbers from 2 till n)
#include<stdio.h>
int main()
{
int i,n;
printf(“enter n:”);
scanf(“%d”,&n);
for(i=2;i<=n;i=i+2)
{
printf(“%d\t”,i);
}
return 0;
}
Program (print the sum of first n numbers)
#include<stdio.h>
int main()
{
int i,n,sum=0;
printf(“enter n:”);
scanf(“%d”,&n);
for(i=1;i<=n;i++)
{
sum=sum+i;
}
printf(“sum=%d”,sum);
return 0;

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}
Program (print the factorial of n)
#include<stdio.h>
int main()
{
int i,n,f=1;
printf(“enter n:”);
scanf(“%d”,&n);
for(i=1;i<=n;i++)
{
f=f*i;
}
printf(“factorial of %d =%d”,n,f);
return 0;
}
Additional Features of for loop
1. More than one variable can be initialized at a time in the for statement.
for (p=1,n=0; n<17; ++n)
2. Like the initialization section, the increment section may also have more than one part. For example
the loop
for(n=1, m=50; n<=m; n=n+1, m=m-1)
{
p=m/n;
printf(“%d %d %d\n”, n, m, p);
}
is perfectly valid. The multiple arguments in the Increment section are separated by commas.
3. The third feature is that the test-condition may have any compound relation and the testing need not
be limited only to the loop control variable. Consider the example below:
sum 0;
for (i =1; i < 20 && sum < 100; ++i)
{
sum = sum+i;
printf("%d %d\n”, i, sum);

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}
4. Another unique aspect of for loop is that one or more sections can be omitted, if necessary.
Consider the following statements
m=5;
for (; m !=100;)
{
printf(“%d\n”,m);
m=m+5;
}
5. we can set up time delay using the null statement(;) as follows:
for(i=1;i<=1000;i++);
The loop is executed 1000 times without producing any output; it simply causes a time delay.
Nesting of for loop
Nesting of for loops that is one for statement within another for statement, is allowed in C. For example
two loops can be nested as follows:
Syntax:

Write a C program using nested for loop to print the following pattern.
i) * ii) * * * *
* * * * *
* * * * *
* * * * *
#include<stdio.h>
int main()
{
int i,j;
for (i=1;i<=4; i++)
{
for (j=1;j<=i; j++)
{
printf(“*\t”);

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}
printf(“\n”);
}
return 0;
}
#include<stdio.h>
int main()
{
int i,j;
for (i=4;i>=1; i--)
{
for (j=1;j<=i; j++)
{
printf(“*\t”);
}
printf(“\n”);
}
return 0;
}
Just like for loop, even while and do while can be nested.
#include<stdio.h>
int main()
{
int x,y,sum;
x=1;
while(x<=2)
{
y=1;
while(y<=2)
{
sum=x+y;
printf(“\nx=%d”,x);
printf(“\ny=%d”,y);

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printf(“\nsum=%d”,sum);
y++;
}
x++;
}
}
Output:
x=1
y=1
sum=2
x=1
y=2
sum=3
x=2
y=1
sum=3
x=2
y=2
sum=4
Decision Making and Unconditional jump statements in C:
goto, break, continue, exit, return
THE GOTO STATEMENT
The goto requires a label in order to identify the place where the branch is to be made. A label is any valid
variable name, and must be followed by a colon. The label is placed immediately before the statement
where the control is to be transferred.
Syntax:

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During running of a program when a statement like - goto begin; is met, the flow of control will jump to
the statement immediately following the label begin: This happens unconditionally.
If the label: is before the statement goto label; a loop will be formed and some statements will be executed
repeatedly. Such a jump is known as a backward jump. On the other hand, if the label: is placed after the
goto label; some statements will be skipped and the jump is known as forward jump.

Program (use goto to write a program to perform the sum of first n natural numbers) -
Backward jump works like loop.

#include<stdio.h>
int main()
{
int i,n,sum;
printf(“enter n”);
scanf(“%d”,&n);
sum=0;
i=0;
loop:
sum=sum+i;
i=i+1;
if(i<=n)
goto loop;
printf(“sum=%d”, sum);
return 0;
}

Program (use goto to write a program to check if the input marks is pass or fail)

#include<stdio.h>

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int main()
{
int marks;
printf(“enter marks”);
scanf(“%d”,&marks);
if(marks<50)
goto fail;
else
goto pass;
fail:
printf(“failed”);
exit(0);
pass:
printf(“passed”);
return 0;
}
Avoiding goto
It is a good practice to avoid using goto. Using many of them makes a program logic complicated and
renders the program unreadable. The goto jumps shown in below fig would cause problems and therefore
must be avoided

Fig: Avoid goto

Jumping out of a loop using break statement
An early exit from a loop can be accomplished by using the break statement or the goto statement.
Syntax for break: break;
These statements can also be used within while, do, or for loops. When a break statement-is encountered
inside a loop, the loop is immediately exited and the program continues with the statement immediately
following the loop.

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Program (to print first 10 even numbers not greater than 10)
#include<stdio.h>
int main()
{
int i;
for(i=2;i<=20;i=i+2)
{
if(i>10)
break;
printf(“%d\t”,i);
}
return 0;
}
Skipping a part of loop using continue statement
During the loop operations, it may be necessary to skip a part of the body of the loop under certain
conditions. Unlike the break which causes the loop to be terminated, the continue, causes the loop to be
continued with the next iteration after skipping any statements in between. The continue statement tells the
compiler, "SKIP THE FOLLOWING STATEMENTS AND CONTINUE WITH THE NEXT
ITERATION". The format of the continue statement is simply
Syntax:
continue;
The use of the continue statement in loops is Illustrated

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Program (to print first 10 even numbers except 6 and 8)

#include<stdio.h>
int main()
{
int i;
for(i=2;i<=20;i=i+2)
{
if(i==6||i==8)
continue;
printf(“%d\t”,i);
}
return 0;
}
Jumping out of the program – exit()
We have just seen that we can jump out of a loop using either the break statement or goto statement. In a
similar way, we can jump out of a program by using the library function exit( ). In case, due to some reason,
we wish to break out of a program and return to the operating system, we can use the exit() function, as
shown below
…………
………...
if (test-condition)
exit(0);
………..
………..
The exit() function takes an integer value as its argument. Normally zero is used to indicate normal
termination and a nonzero value to indicate termination due to some error or abnormal condition. The use of
exit() function requires the inclusion of the header file <stdlib.h>
Return statement: return statement terminates the execution and returns control to the calling function.
Syntax: return expression;

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Example: return 0; 0 will be returned to calling function.

Chapter 1: Operators in C, Type Conversion and Typecasting
An expression is a sequence of operands and operators that reduces to a single value.
An operation is specified as an expression that reduces to a single value.
An operand is the data item on which an operation is done.
An operator is a symbol that tells computer to perform certain mathematical or logical operations.
An operation can be unary, binary or ternary. Unary consists of single operand, Binary consists of two
operands and ternary consists of three operands. All operations have at least one operator.
C operators can be classified into number of categories. They include:
1) Arithmetic operators
2) Relational operators
3) Logical operators
4) Assignment operators
5) Increment and decrement operators
6) Conditional operators
7) Bitwise operators
8) Special operators

1 ARITHMETIC OPERATORS
C provides all the basic arithmetic operators. The operators +,-,*, and / all work the same way as
they do in the other languages. The unary minus operator, in effect, multiples its single operand by -1. Therefore,
a number preceded by a minus sign changes its sign.

Integer division truncates any fractional part. The modulo division operation produces the remainder of
an integer division. Examples of use of arithmetic operators are:
a-b a+b
a*b a/b
a%b -a*b
Here a and b are variables and are known as operands. The modulo division operator % cannot be used on
floating point data.
Integer Arithmetic

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When both the operands in a single arithmetic expression such as a+b are integers, the expression is
called an integer expression, and the operation is called integer arithmetic. Integer arithmetic always yields
an integer value. The largest integer values depends on the machine, as pointed out earlier. In the above
examples, if a and bare integers, then for a=14 and b=4 we have the following results:
a – b = 10
a + b = 18
a * b = 56
a / b = 3 (decimal part truncated)
a % b = 2 (remainder of division)
Similarly, during modulo division, the sign of the result is always the sign of the first operand (the
dividend). That is,
-14 % 3 = -2
-14 % -3 = -2
14 % -3 = 2
Real Arithmetic / Floating Point arithmetic
An arithmetic operation involving only real operands is called real arithmetic. If x, y, and z are floats,
then we will have:
x = 6.0 / 7.0 = 0.857143
y = 1.0 / 3.0 = 0.333333
z = -2.0 / 3.0 = -0.666667
The operator % cannot be used with real operands.
Mixed-mode Arithmetic
When one of the operands is real and the other is integer, the expression is called a mixed-mode
arithmetic expression. If either operand is of the real type, then only the real operation is performed and the
result is always a real number. Thus
15 / 10.0 = 1.5
Whereas
15 / 10 = 1
Program: Addition of two numbers
#include<stdio.h>
int main()
{
int a=10,b=20,c;

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c=a+b;
printf(“result=%d”,c);
return 0;
}
2 RELATIONAL OPERATORS
We often compare two quantities depending on their relation, take certain decisions. These
comparisons can be done with the help of relational operators. We have already used the symbol ‘<’ ,
meaning ‘less than’. An expression such as
a<b or 1<20
Containing a relational operator is termed as a relational expression. The value of a relational expression is
either one or zero. It is one if the specified relation is true and zero if the relation is false.
For example
10 < 20 is true
but
20 < 10 is false
C supports six relational operators in all. These operators and their meanings are shown under.

A simple relational expression contains only one relational operator and takes the following form:
ae-1 relational operator ae-2
ae-1 and ae-2 are arithmetic expressions, which may be simple constants, variables or combination of them.
4.5 <= 10 TRUE
4.5 <-10 FALSE
When arithmetic expressions are used on either side of a relational operator, the arithmetic expressions will
be evaluated first and then the results compared. That is, arithmetic operators have a higher priority over
relational operators.
Relational Operator Complements
Among the six relational operators, each one is a complement of another operator.
> is complement of <=
< is complement of >=
== is complement of !=
We can simplify an expression involving the not and the less than operators using the complements as

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shown below:
Actual one Simplified one
!(x < y) x >= y
!(x > y) x <= y
!(x != y) x == y
!(x <= y) x>y
!(x >= y) x<y
!(x == y) x != y
Program: Greatest of two numbers
#include<stdio.h>
int main()
{
int a,b;
printf(“enter two numbers”);
scanf(“%d%d”,&a,&b);
if(a>b)
printf(“%d is greatest”,a);
else
printf(“%d is greatest”,b);
return 0;
}
3 LOGICAL OPERATORS
In addition to the relational operators, C has the following three logical operators.
&& meaning logical AND
|| meaning logical OR
! meaning logical NOT or Logical negation
The logical operators && and | | are used when we want to test more than one condition and make decisions.
An example is:
a > b && x==10
An expression of this kind, which combines two or more relational expressions, is termed as a logical
expression.

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op1 !op1
0 1
1 0
Program: Greatest of three numbers
#include<stdio.h>
int main()
{
int a,b,c;
printf(“enter three numbers”);
scanf(“%d%d%d”,&a,&b,&c);
if((a>b)&&(a>c))
printf(“%d is greatest”,a);
else if(b>c)
printf(“%d is greatest”,b);
else
printf(“%d is greatest”,c);
return 0;
}
4 ASSIGNMENT OPERATORS
Assignment operators are used to assign the result of an expression to a variable. We have seen the usual
assignment operator, ‘=’.
v =exp;
In addition, C has a set of ‘shorthand’ assignment operators of the form:
v op= exp;
Where v is a variable, exp is an expression and op is a C binary arithmetic operator. The operator op= is
known as the shorthand assignment operator.
The assignment statement
v op= exp;
is equivalent to
v = v op (exp);

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Consider an example x += y;
This is the same as the statement x = x + y;

Example/
Operators Description

sum = 10;
10 is assigned to
= variable sum

a += 10;
This is same as a = a
+= + 10

a - = 10;
This is same as a = a
-= – 10

a *= 10;
This is same as a = a
*= * 10

a /= 10;
This is same as a =
/= a / 10

a %= 10;
This is same as a = a
%= % 10

a &= 10;
This is same as a = a
&= & 10

|= a |= 10;
This is same as a = a

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| 10

a ^= 10;
This is same as a = a
^ ^ 10

a <<= 10;
This is same as a = a
<< << 10

a >>= 10;
This is same as a = a
>> >> 10

The use of shorthand assignment operators has three advantages:

1. What appears on the left-hand side need not be repeated and therefore it becomes easier to write.
2. The statement is more concise and easier to read.
3. The statement is more efficient.

Program: Addition of two numbers

int main()
{
int a=10,b=20;
a+=b;
printf(“result=%d”,a);
return 0;
}
5 INCREMENT AND DECREMENT OPERATORS
The increment and decrement operators:
++ and– –
The operator ++ adds 1 to the operand, while – – subtracts 1. Both are unary operators and takes the
following form:
++a; or a++;
– –a; or a– –;
++a; is equivalent to a = a+1; (or a +=1; )
– –a; is equivalent to a = a-1; (or a – =1; )

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A prefix operator first adds 1 to the operand and then the result is assigned to the variable on the left. On
the other hand, a postfix operator first assigns the value to the variable on left and then increments the
operand.
y=++x x=x+1 y=x++ y=x
y=x x=x+1
Ex : x=10 Ex : x=10
x=11 y=10
y=11 x=11

y=--x x=x-1 y=x-- y=x

y=x x=x-1
Ex : x=10 Ex : x=10
x=9 y=10
y=9 x=9

Program:
#include<stdio.h>
int main()
{
int a=10;
printf(“%d”,a++);
return 0;
}
Output: 10
6 CONDITIONAL OPERATOR
A ternary operator pair “? :” is available in C to construct conditional expressions of the form
exp1 ?exp2 : exp3
where exp1, exp2 and exp3 are expressions.
The operator ? : works as follows: exp1 is evaluated first, if it is nonzero (true), then the expression exp2 is
evaluated and becomes the value of the expression. If exp1 is false, exp3 is evaluated and its value becomes
the value of the expression.
a = 10;

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b = 15;
big = (a>b) ?a : b;
In this example, big will be assigned the value of b. This can be achieved using the if..else statements as
follows:
if (a > b)
big = a;
else
big = b;
Program: Smallest of two numbers
int main()
{
inta,b,small;
printf(“enter two numbers”);
scanf(“%d%d”,&a,&b);
small=a<b?a:b;
printf(“%d is smallest”,small);
return 0;
}
Program: Smallest of three numbers
int main()
{
inta,b,c,small;
printf("enter three numbers");
scanf("%d%d%d",&a,&b,&c);
small=a<b&&a<c?a:(b<c?b:c);
printf("%d is smallest",small);
return 0;
}
7 BITWISE OPERATORS
C has special operators known as bitwise operators for manipulation of data at bit level. These operators
are used for testing the bits, or shifting them right or left. Bitwise operators may not be applied to float
or double. (bitwise complement ~ is also a bitwise operator which complements the bit (ie)
complement of 0 is 1, complement of 1 is 0.)

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op1 op2 op1&op2 op1|op2 op1^op2

0 0 0 0 0
0 1 0 1 1
1 0 0 1 1
1 1 1 1 0

op1 ~op1
0 1
1 0

8&2=0 (i.e 1000&0010=0000)

8|2=10 (i.e 1000|0010=1010)
8^2=10 (i.e 1000^0010=1010)
8<<2=32 (shift bit by bit)
1000
10000(by one bit to left)
100000(by next one bit to left)=32
8>>2=2 (shift bit by bit)
1000
0100(by one bit to right)
0010(by next one bit to right )=2
Program:
int main()
{
int a=8,b=2;
printf("%d", a&b);
return 0;
}
8 SPECIAL OPERATORS

C supports some special operators such as comma operator, sizeof operator, pointer operators (& and

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*) and member selection operators (. and –>)

The Comma Operator
The comma operator can be used to link the related expressions together. A comma-linked list of
expressions are evaluated left to right and the value of right-most expression is the value of the value of
the combined expression. For example, the statement:
value = ( x = 10, y=5, x+y );
first assigns the value 10 to x, then assigns 5 to y, and finally assigns 15 (i.e. 10 + 5) to value. Since
comma operator has the lowest precedence of all operators, the parentheses are necessary. Some
applications of comma operator are:
The sizeof Operator
The sizeof returns the number of bytes the operand occupies. The operand may be a variable, a constant
or a data type qualifier.
Examples:
m = sizeof(int); 2 bytes in a 16-bit machine
n =sizeof(long int); 4 bytes in a 16-bit machine
k=sizeof(100); 2 bytes in a 16-bit machine
Program:
#include<stdio.h>
int main()
{
printf("size of integer is %d”,sizeof(int));
return 0;
}
Mathematical functions
Mathematical functions such as cos, sqrt, log, etc. are frequently used in analysis of real-life problems.
Most of the C compiles support these basic math functions. To use these functions in a program, we
should include the line:
#include <math.h> in the beginning of the program.
Some of the Math functions are
 cos(x) cosine of x
 sin(x) sine of x
 tan(x) tangent of x
 cosh(x) hyberbolic cosine of x

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 sinh(x)hyperbolic sine of x
 tanh(x) hyperbolic tangent of x
 ceil(x) x rounded to nearest integer
 exp(x) e to the x power (ex)
 abs(x) absolute value of x
 fabs(x)absolute value of float x
 log(x) natural log of x, x>0
 pow(x,y) x to the power y (xy)
 sqrt(x) square root of x, x>=0
ARITHMETIC EXPRESSIONS
An arithmetic expression is a combination of variables, constants, and operators arranged as per the
syntax of the language. C can handle any complex mathematical expressions. Some of the examples of
C expressions are shown below:

OPERATOR PRECEDENCE AND ASSOCIATIVITY

C operators has a precedence associated with it. This precedence is used to determine how an expression
involving more than one operator is evaluated. There are distinct levels of precedence and an operator may
belong to one of these levels. The operators at the higher level of precedence are evaluated first. The
operators of the same precedence are evaluated either from ‘left to right’ or from ‘right to left’, depending
on the level. This is known as the associativity property of an operator. Rank 1 indicates the highest
precedence level and 15 the lowest.
Rules of precedence and Associativity
 Precedence rules decides the order in which different operators are applied
 Associativity rule decides the order in which multiple occurrences of the same level operator are
applied.

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