Mesics lecture 6 control statement = if -else if__else

Control Statement in C

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TYPES OF PROGRAMMING
STRUCTURE
•All modern programming languages include
support for three basic families of programming
structures:
•Sequential structures
•Decision structures
•Looping structures

WHAT IS A DECISION STRUCTURE?

•Decision structures consist of:
•Some type of T/F test
•One or more executable blocks of code
•Which block of code executes depends on the
result of the T/F test (“the condition”).

CONTROL STATEMENT

•All the statements written in ‘C’ program executes
from top to bottom one by one
•Control statements are used to execute or transfer
the execution control from one part of the program
to another part based on a conditions, Such
statements are known as Conditional Statements

CONTROL STATEMENT

•There are three types of control statements
used in C language
1.if-else statement
2.switch statement
3.goto statement

IF / ELSE IF / ELSE SELECTION
STRUCTURES
1) A simple if structure is called a single-selection
structure because it either selects or ignores a
single action.

2) The if / else structure is called a double-selection
structure because it selects between two different
actions.

3) Nested if / else structures test for multiple cases
by placing if / else structures inside other if / else
structures.

RELATIONAL OPERATORS

To develop valid conditions, we need to use
relational operators.
Operator Meaning Operator Meaning

> Greater Than <= Less Than or Equal to

Greater Than or
>= == Equality
Equal to

< Less Than != Inequality

IF-ELSE STATEMENT

•It is used to execute a set of statements or single
statement based on the evaluation of given
condition
•It is basically a two way decision statement and is
used in conjunction with an expression

SIMPLE IF STATEMENT

syntax :if(expression)
{
statement 1;
statement 2;
.
True
statement N;
}
statement-x;
Note : If expression is true than the set of statements will be
executed after that statement-x will also be executed.
Otherwise, the set of statements will be skipped and
statements-x will be executed.

Result of expression

•Based on the True Non-Zero
evaluation of the
conditional expression
the result will be as
follow
False Zero

EXAMPLE
void main()
{
int i=5;
if(i==5)
{
printf(“You are inside the if true block”);
printf(“nvalue of i is equal to 5”);
}
printf(“nYou are outside the if block”);
}
output :
You are inside the if true block
value of i is equal to 5
You are outside the if block

EXAMPLE
void main()
{
int i=-5;
if(i==5)
{
printf(“You are inside the if true block”);
printf(“nvalue of i is equal to 5”);
}
printf(“nYou are outside the if block”);
}
output :
You are outside the if block

IF-ELSE STATEMENT SYNTAX
if (expression)
{
statement 1;
True statement 2;
.
.
statement N;
}
else
{
statement 1;
statement 2;
. False
.
statement N;
}

IF-ELSE STATEMENT SYNTAX

The if selection structure is often written as:

if ( this logical expression is true ) no semi-colon!
statement ;

And, the if / else selection structure is often written as:

if ( this logical expression is true )
statement ;
else
statement ;

A VERY SIMPLE PROGRAM:

#include <stdio.h>
int main ( )
{
int a = 1, b = 2, c ;

if (a > b)
{
c = a;
}
else
{
c = b;
}
}

A VERY SIMPLE PROGRAM:

#include <stdio.h>
int main ( )
{
int a = 1, b = 2, c ;

if (a > b)
c = a;
else
c = b;
}

IF…ELSE IF…ELSE STATEMENT

•To perform multi-path decisions
•It is collection of if statement with association of
else statement

IF…ELSE IF…ELSE STATEMENT -
SYNTAX
if(expression1)
{
statement 1;
}
else if(expression2)
{
statement 2;
}
else if(expression3)
{
statement 3;
}
else
{
statement 4; //Also known as default
statement
}

IF…ELSE IF…ELSE STATEMENT

•The structure is also known as else if ladder
•The conditions are evaluated from top of the ladder
to downwards
•if the expression1 evaluates to true than all the
statements in this block will executed
•Execution pointer will jump to the statement
immediately after the closing curly braces
•If all the given conditions evaluates to false than all
the statements in else block will be executed
•Else block is also known as default statement

IF…ELSE IF…ELSE STATEMENT -
EXAMPLE
void main()
{
int num;
num=4;
if(num>1)
{
printf(“It is positive value”);
}
else if(num<1)
{
printf(“It is negative value”);
}
else
{
printf(“It is zero value”):
}
getch();
}

EXAMPLE

•WAP to accept marks for 5 subjects from the user,
calculate total and percentage and find the result as
per the following criteria
Criteria Result
Greater than or equal to 70 Distinction
Between 60-70 First Class
Between 50-60 Second Class
Between 40-50 Pass Class
Less than 40 Fail

EXAMPLE

Calculate the comission of a salesman considering
three regions X,Y and Z depending on the sales
amount as follow
Area Code Sales Amount Comission
X <1000 10%
<5000 12%
>=5000 15%
Y <1500 10%
<7000 12%
>=7000 15%
Z <1200 10%
<6500 12%
>=6500 15%

EXAMPLE

•Big Bazzar gives festival discount on purchase of
their products in the following percentages
i.If purchase amount < 1000 than 5% discount
ii.If purchase amount >=1000 than but <3000 then
10% discount
iii.If purchase amount >=3000 but <5000 then 12%
discount
iv.If purchase amount > 5000 then 15% discount

Mesics lecture 6 control statement = if -else if__else

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