Intro to Programming Week # 4
If-else Statement Lecture # 6
By: Saqib Rasheed
Department of Computer Science & Engineering Air University
Control Structures
3 control structures
Sequence structure
Programs executed sequentially by default
Selection structures (conditional instructions)
if, if/else, switch
Repetition structures (loop/jump instructions)
while, do/while, for
Flow Chart for if statement
if Statement
if (condition) {
statement ; -
- }
The if statement allows conditional execution
Practice Example # 1
main () {
int num;
cout<<“Enter a number less than 10:”;
cin>>num;
If (num <10) {
cout<<“What a obedient students”
} }
Relational Operators
The relational operators allow to compare two values
Whether they are equal to each other.
Unequal
Whether one is greater than the other.
Relational Operators
We can even use arithmetic expressions in the if statement.
if ( 3 + 2 % 5 ) {
cout<<"This works";
}
if ( a = 10 ) {
cout<<"Even this works";
}
if ( -5 ){
cout<<"Surprisingly even this works";
}
int var1, var2;
cout<<"Input the first number:";
cin>>var1;
cout<<"Input the second number:";
cin>>var2;
if(var1 == var2) {
cout<<"var1 is equal to var2";
}
Practice Example # 2
Apply all relational operators
if-else
Entry point for if-else block
Exit point for if-else block
if-else
if (condition) {
statement ; -
- } else {
statement ; -
- }
Practice Example # 4
cout<<“Enter a number less than Equal to 10:”;
cin>>num;
If (num <=10) {
cout<<“What a obedient students”
}
else {
cout<<“You are not obedient Student”;
}
int var1, var2;
cout<<"Input the first number:";
cin>>var1;
cout<<"Input the second number:";
cin>>var2;
if(var1 == var2) {
cout<<"var1 is equal to var2";
} else {
cout<<"var1 is not equal to var2";
}
Practice Example # 5
Example Nested if
int var1,var2,var3,var4;
var1=12;
var2=12;
var3=10;
var4=10;
if(var1 == var2) {
cout<<"\nOuter Loop Statement";
if (var3 == var4) {
cout<<"\nVar1 & Var2 are Equal and Var3 & var4 are Equal";
} }
cout<<"\nMain Statement";
Largest Number among 3
Write a program in C++ that take input of three integers numbers from user.
Find the largest number among three of them.
Largest Number among 3
(Code)
#include<iostream.h>
void main () {
int a,b,c, larg;
cout<<"Enter First Integer=";
cin>>a;
cout<<"Enter Second Integer=";
cin>>b;
cout<<"Enter Third Integer=";
cin>>c;
Largest Number among 3
(Code)
if (a > b)
larg = a;
else
larg = b;
if (larg > c )
cout<<"Largest is ="<<larg<<endl;
else
cout<<"Largest is ="<<c<<endl;
}
Nested if else Statement
If (condition) {
do this;
}
else if(condition) {
do this;
}
Nested if else Statement
If (condition) {
do this;
}
else if(condition) {
do this;
} else {
do this;
}
Nested if else
Example of nested if else
marks >= 90 Grade A marks >= 80 Grade B marks >=70 Grade C marks >=60 Grade D
Nested if else (Code)
int main ()
{ //start of main function int marks;
cout<<"Enter the grade of student=";
cin>>marks;
if ( marks >= 90 )
cout<< " Grade A \n";
else if (marks >= 80 )
cout<<" Grade B \n";
Nested if else (Code)
else if ( marks >=70 )
cout<<" Grade C \n";
else if (marks >=60)
cout<<" Grade D \n";
else {
cout<<" Grade F \n";
cout<<" You have to take the classes again\n";
cout<<" Work Hard To Get Good Grade\n";
}
return 0;
} // end of main function
Nested if / if-else example
int n1,n2,n3;
cout << "Enter three integers: ";
cin >> n1 >> n2 >> n3;`
if (n1 < n2)
if (n1 < n3) `
cout << "Their minimum is " << n1 << endl;
else
cout << "Their minimum is " << n3 << endl;
else if (n2 < n3)
cout << "Their minimum is " << n2 << endl;
else
cout << "Their minimum is " << n3 << endl;
Forms of if
The if statement can take any of the following forms:
(a) if ( condition )
do this ;
(b) if ( condition ) {
do this ; and this ; }
(c) if ( condition ) do this ;
else if (condition) do this ;
Forms of if -else
(c) if ( condition ) do this ;
else if (condition) do this ;
else
do this;
Forms of if -else
(d) if ( condition ) {
do this ; and this ; }
else {
do this ; and this ; }
Forms of if -else
(e) if ( condition ) do this ;
else {
if ( condition ) do this ;
else {
do this ; and this ; }
}
Forms of if -else
(f) if ( condition ) {
if ( condition ) do this ;
else {
do this ; and this ; }
} else
do this ;
Forms of if -else
(d) if ( condition ) ; {
do this ; and this ; }
Logical error
Semicolon does not come hear
Logical Operators
AND &&
OR ||
Not !
Bitwise Operator
|
&
Logical Operators
If a is greater than b
AND c is greater than d
In C++
if(a > b && c> d)
if(age > 18 || height > 5)
The Conditional Operators
The conditional operators ? and : are sometimes called ternary operators
since they take three arguments
expression 1 ? expression 2 : expression 3
Example of Condition Operator
int x, y ; cin>>x;
y = ( x > 5 ? 3 : 4 ) ;
This statement will store 3 in y if x is greater than 5, otherwise it will store 4 in y.
Hierarchy of Operators
Assignment
Write a program to calculate the salary as per the following table
Practice examples with code
Vowel / Consonant
Write a program in C++ to input a single character and print a message“ It is
vowel" if it is vowel otherwise print message "It is a "consonant“ Use if-else structure and
OR (||) operator only
Vowel / Consonant (Code)
int main() { char input;
cout<<"Input a single character-->";
cin>>input;
if (input == 'a' || input == 'e'|| input == 'i' ||input == 'o'|| input == 'u‘) cout<<"Its a VOWEL\n“;
else
cout<<"Its a CONSONANT\n“;
}
Odd/ Even
Write a Program in C++ that take an Integer value’s from the user and tell that the number Is EVEN or ODD
Odd/ Even (Code)
int value;
cout<<"Enter an Interger value ";
cin>>value;
if (value % 2 == 0)
cout<<"Your number is Even\n";
else
cout<<"Your number is Odd\n“;
Small / Capital Letter
Write a program in C++ that take a single
character from the user, and tells it's a Small Letter or it's a CAPITAL letter using nested if statement only
Small / Capital Letter (Code)
char letter;
cout<<"Enter the letter in \"CAPITAL\" or in \"SMALL\"-->";
cin>>letter;
if (letter >='A' && letter <= 'Z') {
cout<<"\n\nYou Entered a Capital Letter\n";
if (letter == 'a' || letter == 'e'|| letter == 'i' || letter == 'o'|| letter == 'u' ||
letter == 'A' || letter == 'E'|| letter == 'I' || letter == 'O'|| letter == 'U') cout<<"\n\nIts a VOWEL\n";
else
cout<<"\n\nIts a CONSONANT\n“;
}
Small / Capital Letter (Code)
else if (letter >= 'a' && letter <= 'z') {
cout<<"\n\nYou Entered a Small Letter\n";
If (letter == 'a' || letter == 'e'|| letter == 'i' || letter == 'o'|| letter =='u' ||
letter == 'A' || letter == 'E'|| letter == 'I' || letter == 'O'|| letter == 'U') cout<<"\n\nIts a VOWEL\n";
else
cout<<"\n\nIts a CONSONANT\n“;
}
else cout<<"\n\nIts Not a letter";
cout<<endl;
return 0; }
Condition Operator (?:)
Write a Program in C++ to input a single letter in a char variable. If "m" is input print "You are Male” otherwise "You are Female" by Using Condition Operator (?:)
Condition Operator (?:)
int main () {
char gender;
cout<<"Enter the Gender of the Person=";
cin>>gender;
/*(?:) First Value is Printed if the condition
is true and if it is false second condition is printed*/
cout<<( gender>= 'm' ? "You are Male\n" : "You are Female\n");
}