Some Slides for C language by Abdul Rehman

1. Computer Programming:
C language
Subject Teacher:
Abdul Rehman
Lecture – 17 & 18

2. The Decision Control Structure
• Decision making statements are used to skip or to execute a group of
statements based on the result of some condition.
• The decision making statements are,
− simple if statement
− if…else statement
− nested if
− else … if ladder
− switch statement
− goto
• These statements are also called branching statements

3. IF Statement
• if statement executes a single statement or a block of statements if a
boolean expression evaluates to true.
Syntax:
If(condition)
{
Statements;
}
Here condition is a boolean expression
If condition is true, then the statement is executed
If condition is false, than the statement is bypassed

4. Simple if statement
Syntax:
if(condition)
{
Statements;
}
if(condition)
Statements;
False
True (Bypass)

5. Simple if - Example
#include<stdio.h>
#include<conio.h>
int main()
{
int num1,num2;
printf("Enter any two numbers ");
scanf("%d %d",&num1,&num2);
if(num1>num2)
printf("nNum1 is greater than Num2");
printf("nEnd of program");
getch();
}
Output1
Enter any two numbers 10 5
Num1 is greater than Num2
End of program
Output1
Enter any two numbers 10 50
End of program

6. IF Else Statement
• An if statement can include an else clause that executes a statement or block
if the boolean expression is not true.
Syntax:
If (condition)
Statement1;
Else
Statement2;
• If condition is true, then statement1 is executed.
• Otherwise, statement2 is executed.

7. if - else statement
Syntax:
if(condition)
{
True block statements;
}
else
{
False block statements;
}
if(condi
tion)
True Block
Statement
False
True
False Block
Statements

8. if – else Example
# include <stdio.h>
void main ()
{
int num;
printf ("Type a number:");
scanf ("%d", &num);
if (number < 0)
printf(“The number is negative”);
else
printf(“The number is positive”);
}
Output
Type a number 50
The number is positive

9. if – else Example
#include<stdio.h>
void main()
{
Int num;
printf ("Enter a number:");
scanf ("%d",&num);
if (num%2==0)
printf ("The number is
EVEN.n");
else
printf ("The number is
ODD.n");
}
Output
Enter a number 125
The number is ODD

10. if – else Example
#include<stdio.h>
#include<conio.h>
void main (void)
{
int percentage;
printf(“Enter your percentage: “);
scanf(“%d”, &percentage);
if(percentage>=60)
printf(“You are Passed”);
else
printf(“You are failed”);
getch();
}

11. Else - if Ladder Statement
• An if statement can be followed by an optional else
if...else statement, which is very useful to test various
conditions using single if...else if statement.
When using if , else if , else statements there are few points to
keep in mind:
• An if can have zero or one else's and it must come after any
else if's.
• An if can have zero to many else if's and they must come
before the else.
• Once an else if succeeds, none of the remaining else if's or
else's will be tested.

12. Else - if Ladder Statement
Syntax
if (condition1)
statement block 1;
else if (condition2)
statement block 2;
else if (condition3)
statement block 3;
:
:
else if (condition)
statement block n;
else
default statement;

13. Else - if Ladder Statement
If(condition1)
Default Statements;
True
False
Statements1;
Else if(condition2)
True
Statements2;
False
Else if(condition3)
Statements3;
False
True

14. Else - if Ladder Example
#include<stdio.h>
#include<conio.h>
void main(void)
{
int num1,num2;
clrscr();
printf(“Enter integer numbers to check: ”);
scanf(“%d %d”,&num1,&num2);
if(num1>num2)
printf(“num1 is greater than num2”);
else if(num1<num2)
printf(“num1 is less than num2”);
else
printf(“both numbers are equal”);
getch();
}

15. Else - if Ladder Example
#include <stdio.h>
void main ()
{
float perc;
printf ("Enter Percentage:");
scanf ("%f", &perc);
if (perc <= 100 && perc >= 80)
printf ("n A-1 Grade");
else if (perc >= 70)
printf("n A Grade");
else if (perc >= 60)
printf ("n B Grade");
else
printf ("Fail");
}
Output
Enter Percentage: 75
A Grade

16. Else - if Ladder Example
#include<stdio.h>
#include<conio.h>
int main()
{
float num1, num2; char op;
printf("Enter two numbers");
scanf("%f %f",&num1,&num2);
printf("nEnter operator (+,-,*,/)");
op=getche();
if(op =='+')
printf("nResult=%f",num1+num2);
else if(op == '-')
printf("nResult=%f",num1-num2);
else if(op == '*')
printf("nResult=%f",num1*num2);
else if(op == '/')
printf("nResult=%f",num1/num2);
else
printf("Invalid Operator");
getch(); }