Control Statement programming

Introduction
We have seen that a C program is a set of statement which are
normally executed in order which they appear. This happens when
no options or no repetitions in calculations are necessary.
However in practice we have a number of situations, where we
may have to change the order of execution of statements based
on certain conditions, or repeat a group of statements until
certain specified conditions are met.
This involves a kind of decision making to see whether a particular
conditions has occurred or not and then direct the computer to
execute certain statements accordingly.

C language processes such decision-making capabilities by
supporting the following statements.
1. if else statement
2. nested if else statement, if-else-if ladder
3. switch statement, Conditional operator statement
4. goto statement
These statements are popularly known as decision-making
statements. Since these statements ‘control’ the flow execution,
they are also known as control statement.
We have already used some of these statements in the earlier
examples. Here, we shall discuss their features, capabilities and
applications in more detail.

THE IF….ELSE STATEMENT
The if...else statement is an extension of the simple if statement. The general from is
If the test expression is true ,then the true-block statement(s), immediately following the if
statement are execute; otherwise, the false-block statement are executed, not both .this is
illustrated in fig in both the cases , the control is transferred subsequently to the statement.
if (test expression)
{
true-blockstatement(s)
}
else
{
false-blockstatement(s)
}
statement-x

#include<stdio.h>
int main()
{
int number = 5;
if(number >= 5) {
printf("Your number greater than 5 or
equal to 5n");
}
else{
printf("Your number is smaller than
5n");
}
return 0;
}
+
Code Output

CONCEPT
• The user already assigned the value of number is 5.
• When user run the code the user can see the output Your
number is greater than 5 or equal to 5.

The goto statement
• A goto statement in C language provides an unconditional jump from the goto
to a labeled statement in the same function.
• The given label must reside in the same function.
• Syntax:
• Here label can be any plain text except C keyword and it can be set anywhere
in the C program above or below to goto statement.
NOTE: Use of goto statement is highly discouraged in any programming language
because it makes difficult to trace the control flow of a program, making the
program hard to understand and hard to modify. Any program that uses a goto
can be rewritten so that it doesn't need the goto.

Code Example: goto statement
#include<stdio.h>
int main()
{
int a;
printf("Enter the value of a: ");
scanf("%d", &a);
start:
printf("%dn", a);
a++;
if(a < 10)
goto start;
return 0;
}

Nested if-else Statements
 Using “if…else statement” within another “if…else statement”
is called ‘nested if statement’. “Nested if statements” is
mainly used to test multiple conditions.
 Structure:
if (test_condition){
if (test_condition)
{
statement-block;
}
else
{
statement-block;
}
}else
{
statement-block;
}
statement-x;
Nested if else

Example and the Flowchart of Nested if else
Statements
if (road_status == ‘S’){
if (temp > 0) {
printf(“Wet roads ahead!n”);
}else{
printf(“Icy roads ahead!n”);
}
else
printf(“Drive carefully!n”);
Another if-else statement
Main if-else statement

if-else-if ladder
 The word ladder means the staircase. As the name implies this
statement is used to choose right way among multiple paths.
 Syntax:
if (condition1)
statement1
else if (condition2)
statement2
……………………………
else if (conditionn)
statementn
else
statemente

Example:
if(Mark>=50 && Mark<60)
{ printf("Your grade is D");
}
else if(Mark>=60 && Mark<70)
{ printf("Your grade is C n");
}
{ printf("Your grade is B n");
}
{ printf("Your grade is A n");
}
else
printf("you have failed");

A switch statement allows a variable to be tested for equality
against a list of values. Each value is called a case, and the
variable being switched on is checked for each switch case.
Switch Case:
Flow Diagram :

How it works ?
 Switch case checks the value of expression/variable
against the list of case values and when the match is
found , the block of statement associated with that
case is executed
 Expression should be Integer Expression / Character
 Break statement takes control out of the case.
 Break Statement is Optional.

See how Switch Case works using Graphical
Picture

Control Statement programming

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