Chapter-10 CONTROL STATEMENTS - WordPress.com...Iterative Constructs or Looping Iterative statements...

Chapter 10- Control Statements I PUC, MDRPUC, Hassan

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Chapter-10

CONTROL STATEMENTS

Introduction

Control statements are statements that alter the sequence of flow of instructions.

Any single input statement, assignment and output statement is simple statement.

A group of statement that are separated by semicolon and enclosed within curled braces { and } is

called a block or compound statement.

The order in which statements are executed in a program is called flow of control.

Types of control statements:

C++ supports two basic control statements.

o Selection statements

o Iteration statements

Selection Statements:

This statement allows us to select a statement or set of statements for execution based on some

condition.

It is also known as conditional statement.

This structure helps the programmer to take appropriate decision.

The different selection statements, viz.

o if statement

o if – else statement

o Nested – if statement

o switch statement

if statement :

This is the simplest form of if statement.

This statement is also called as one-way branching.

This statement is used to decide whether a statement or set of statements should be executed or

not.

The decision is based on a condition which can be evaluated to TRUE or FALSE.

The general form of simple – if statement is:

if (Test Condition) // This Condition is true


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Statement 1;

Statement 2;

Here, the test condition is tested which results in either a TRUE or

FALSE value. If the result of the test condition is TRUE then the

Statement 1 is executed. Otherwise, Statement 2 is executed.

Ex: if( amount > = 5000 )

discount = amount * (10/100);

net-amount = amount – discount;

Practical Program 5: Write a C++ program to find the largest, smallest

and second largest of three numbers using simple if statement.

#include<iostream.h>#include<conio.h>void main( ){

int a, b, c;int largest, smallest, seclargest;clrscr( );cout<<”Enter the three numbers”<<endl;cin>>a>>b>>c;largest = a; //Assume first number as largestif(b>largest)

largest = b;if(c>largest)

largest = c;

smallest = a; //Assume first number as smallestif(b<smallest)

smallest = b;if(c<smallest)

smallest = c;

seclargest = (a + b + c) – (largest + smallest);cout<<”Smallest Number is = “<<smallest<<endl;cout<<”Second Largest Number is = “<<seclargest<<endl;cout<<”Largest Number is = “<< largest<<endl;getch( );

}Practical Program 6: Write a C++ program to input the total amount in a bill, if the amount is greater

than 1000, a discount of 8% is given. Otherwise, no discount is given. Output the total amount,

discount and the final amount. Use simple if statement.


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float TAmount, discount, FAmount ;clrscr( );cout<<”Enter the Total Amount”<<endl;cin>>TAmount;

discount = 0; //Calculate Discountif(TAmount>1000)

Discount = (8/100) * TAmount;

FAmount = TAmount – Discount //Calculate Final Amount

cout<<”Toatal Amount = “<<TAmount<<endl;cout<<”Discount = “<<discount<<endl;cout<<”Final Amount = “<< FAmount<<endl;getch( );

} if – else statement :

This structure helps to decide whether a set of statements should be executed or another set of

statements should be executed.

This statement is also called as two-way branching.

The general form of if – else statement is:

if (Test Condition)

Statement 1;

else

Statement 2;

Here, the test condition is tested. If the test-

condition is TRUE, statement-1 is executed.

Otherwise Statement 2 is executed.

Ex: if( n % 2 == 0 )

cout<<” Number is Even”;

else

cout<<” Number is Odd”;

Practical Program 7: Write a C++ program to check whether a given year is a leap year not, Using if

- else statement.


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int year ;clrscr( );cout<<”Enter the Year in the form YYYY”<<endl;cin>>year;if(year%4 ==0 && year%100!=0 || year%400 ==0)

cout<<year<<” is a leap year”<<endl;else

cout<<year<<” is not leap year”<<endl;getch( );

}Practical Program 8: Write a C++ program to accept a character. Determine whether the character is

a lower-case or upper-case letter.


char ch ;clrscr( );cout<<”Enter the Character”<<endl;cin>>ch;if(ch>= ‘A’ && ch <=’Z’)

cout<<ch<<” is an Upper-Case Character”<<endl;elseif(ch>= ‘a’ && ch <=’z’)

cout<<ch<<” is an Lower-Case Character”<<endl;else

cout<<ch<<” is not an alphabet”<<endl;getch( );

} Nested if statement :

If the statement of an if statement is another if statement then such an if statement is called as

Nested-if Statement.

Nested-if statement contains an if statement within another if statement.

There are two forms of nested if statements.

if – else - if statement :

This structure helps the programmer to decide the execution of a statement from multiple

statements based on a condition.


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Example:if( marks > = 85 )

PRINT “Distinction”else

if( marks > = 60 )PRINT “First Class”

elseif( marks > = 50 )

PRINT “Second Class”else

if( marks > = 35 )PRINT “Pass”

elsePRINT “Fail”

There will be more than one condition to test.

This statement is also called as multiple-way branch.

The general form of if – else – if statement is:

if (Test Condition 1)

Statement 1;

else

if (Test Condition 2)

Statement 2;

else

………..

else

if( test Condition N)

Statement N;

else

Default Statement;

Here, Condition 1 is tested. If it is TRUE, Statement 1 is executed control transferred out of the

structure. Otherwise, Condition 2 is tested. If it is TRUE, Statement 2 is executed control is

transferred out of the structure and so on.

If none of the condition is satisfied, a statement called default statement is executed.


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Practical Program 9: Write a C++ program to input the number of units of electricity consumed in a

house and calculate the final amount using nested-if statement. Use the following data for calculation.

Units consumed Cost< 30 Rs. 3.50 / Unit

>= 30 and < 50 Rs. 4.25 / Unit>= 50 and < 100 Rs. 5.25 / Unit

>= 100 Rs. 5.85 / Unit


int units ;float Billamount;clrscr( );cout<<”Enter the number of units consumed”<<endl;cin>>units;if(units < 30)

Billamount = units * 3.50 ;elseif(units < 50)

Billamount = 29 * 3.50 + (units – 29) * 4.25 ;elseif(units < 100)

Billamount = 29 * 3.50 + 20 * 4.25 + (units – 49) * 5.25 ;else

Billamount = 29 * 3.50 + 20 * 4.25 + 50 * 5.25 + (units – 99) * 5.85 ;

cout<<”Total Units Consumed =”<<units<<endl;cout<<”Toatl Amount = “<<Billamount<<endl;getch( );

} The general form of if – else -if statement is:

if (Test Condition 1)if (Test Condition 2)

Statement 1;else

Statement 2;else

if (Test Condition 3)Statement 3;

elseStatement 4;

Ex: To find the greatest of three numbers a, b and c.if ( a>b )

if ( a > c )OUTPUT a

elseOUTPUT c

elseif ( b > c )

OUTPUT belse

OUTPUT c


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Switch Statement :

C++ has built in multiple-branch selection statement i.e. switch.

If there are more than two alternatives to be selected, multiple selection construct is used.

The general form of Switch statement is:

Switch ( Expression )

{

Case Label-1: Statement 1;

Break;

Case Label-2: Statement 1;

Break;

…………..

Case Label-N: Statement N;

Break;

Default : Default- Statement;

}


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Ex: To find the name of the day given the day number

switch ( dayno )

{

Case 1: cout<< “Sunday”<<endl;

break;

Case 2: cout<< “Monday” <<endl;

break;

Case 3: cout<< “Tuesday” <<endl;

break;

Case 4: cout<< “Wednesday” <<endl;

break;

Case 5: cout<< “Thursday” <<endl;

break;

Case 6: cout<< “Friday” <<endl;

break;

Case 7: cout<< “Saturday” <<endl;

break;

default: cout<< “Invalid Day Number” <<endl;

}

The switch statement is a bit peculiar within the C++ language because it uses labels instead of

blocks.

This force up to put break statements after the group of statements that we want to execute for a

specific condition.

Otherwise the remainder statements including those corresponding to other labels also are

executed until the end of the switch selective block or a break statement is reached.

Practical Program 10: Write a C++ program to input the marks of four subjects. Calculate the total

percentage and output the result as either “First Class” or “Second Class” or “Pass Class” or “Fail”

using switch statement.

Class Range (%)First Class Between 60% to 100%

Second Class Between 50% to 59%Pass Class Between 40% to 49%

Fail Less than 40%#include<iostream.h>#include<conio.h>


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void main( ){

int m1, m2, m3, m4, total, choice;float per;clrscr( );cout<<”Enter the First subject marks”<<endl;cin>>m1;cout<<”Enter the Second subject marks”<<endl;cin>>m2;cout<<”Enter the Third subject marks”<<endl;cin>>m3;cout<<”Enter the Fourth subject marks”<<endl;cin>>m4;

total = m1 + m2 + m3 + m4;per = (total / 400) * 100;cout<<”Percentage = “<<per<<endl;

choice = (int) per/10;cout<<”The result of the student is: “<<endl;

switch(choice){

case 10:case 9:case 8:case 7:case 6: cout<<”First Class ”<<endl;

break;case 5: cout<<”Second Class”<<endl;

break;case 4: cout<<”Pass Class”<<endl;

break;default: cout<<”Fail”<<end;

}getch( );

}

Iterative Constructs or Looping

Iterative statements are the statements that are used to repeatedly execute a sequence of statements

until some condition is satisfied or a given number of times.

The process of repeated execution of a sequence of statements until some condition is satisfied is

called as iteration or repetition or loop.

Iterative statements are also called as repetitive statement or looping statements.

There are three types of looping structures in C++.


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o while loop

o do while loop

o for loop

while loop:

This is a pre-tested loop structure.

This structure checks the condition at the beginning of the structure.

The set of statements are executed again and again until the condition is true.

When the condition becomes false, control is transferred out of the structure.

The general form of while structure is

while ( Test Condition)

{

Statement 1

Statement 2

……..

Statement N

}End of While

Example:n = 10;While ( n > 0){

cout<<n<<”\t”;- - n;

}cout<<”End of while loop \n”;Output: 10 9 8 7 6 5 4 3 2 1 End of while loop

Practical Program 11: Write a C++ program to find sum of all the digits of a number using while

statement.


int num, sum, rem;clrscr( );cout<<”Enter the Number”<<endl;cin>>num;sum = 0;


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while(num!=0){

rem = num % 10;sum = sum + rem;num = num/10;

}cout<<”Sum of the digits is “<<sum<<endl;getch( );

}Practical Program 12: Write a C++ program to input principal amount, rate of interest and time

period. Calculate compound interest using while statement.

(Hint: Amount = P * (1 + R/100)T, Compound Interest = Amount – P)


float pri, amt, priamt, rate, ci;int time, year;clrscr( );cout<<”Enter the Principal amount, rate of interest and time”<<endl;cin>>pri>>rate>>time;

year = 1;priamt = pri;

while(year <= time){

amt = pri * (1 + rate/100);year ++;

}ci = amt – priamt;cout<<”Compound Interest is “<<ci<<endl;getch( );

}Practical Program 13: Write a C++ program to check whether the given number is power of 2.


int num, m, flag;clrscr( );cout<<”Enter the Number”<<endl;


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cin>>num;m = num;flag = 1;while(num>2)

if(num % 2 ==1){

flag = 0;break;

}else

num = num/2;if(flag)

cout<<m<<” is power of 2 “<<endl;else

cout<<m<<” is not power of 2 “<<endl;getch( );

} do while statements:

This is a post-tested loop structure.

This structure checks the condition at the end of the structure.

The set of statements are executed again and again until the condition is true.

When the condition becomes false, control is transferred out of the structure.

The general form of while structure is

do

{

Statement 1

Statement 2

……..

Statement N

} while ( Test Condition);

Example:i = 2;do{

cout<<i<<”\t”;i = i + 2;

}while ( i < = 25);


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Practical Program 14: Write a C++ program to check whether the given number is an Armstrong

Number using do-while statement. (Hint: 153 = 13 + 53 + 33)


int num, rem, sum, temp;clrscr( );cout<<”Enter the three digit number”<<endl;cin>>num;temp = num;sum = 0;do{

rem = temp % 10;sum = sum + rem * rem * rem;temp = temp / 10;

}while(temp!=0);if(sum == num)

cout<<num<<” is an Armstrong Number “<<endl;else

cout<<num<<” is not an Armstrong Number “<<endl;getch( );

} Difference between while and do while loop:

while do while

This is pre- tested looping structure This is post tested looping structure

It tests the given condition at initial point

of looping structure

It tests the given condition at the last of

looping structure.

Minimum execution of loop is zero Minimum execution of loop is once.

Syntax:while ( Test condition )

{

statement 1;

statement 2;

…………….;

statement n;

}

Syntax:do

{

statement 1;

statement 2;

statement n;

}

while ( Test condition);Semi colon is not used. Semi colon is used.


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for statement:

This structure is the fixed execution structure.

This structure is usually used when we know in advance exactly how many times asset of

statements is to be repeatedly executed again and again.

This structure can be used as increment looping or decrement looping structure.

The general form of for structure is as follows:

for ( Expression 1; Expression 2; Expression 3)

{

Statement 1;

Statement 2;

Statement N;

}

Where, Expression 1 represents Initialization

Expression 2 represents Condition

Expression 3 represents Increment/Decrement

Example:

sum = 0;

for ( i=1; i<=10; i++)

sum = sum + i;

This looping structure works as follows:

o Initialization is executed. Generally it is an initial value setting for a counter variable and is

executed only one time.

o Condition is checked. if it is TRUE the loop continues, otherwise the loop ends and control

exists from structure.

o Statement is executed as usual, is can either a single statement or a block enclosed in curled

braces { and }.

o At last, whatever is specified in the increase field is executed and the loop gets back to

executed step 2.

o The initialization and increase fields are optional. They can remain empty, but in all cases the

semicolon sign between them must be written compulsorily.

o Optionally, using the comma operator we can specify more than one expression in any of the

fields included in a for loop.


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Practical Program 15: Write a C++ program to find the factorial of a number using for statement.

(Hint: 5! = 5 * 4 * 3 * 2 * 1 = 120)


int num, fact, i;clrscr( );cout<<”Enter the number”<<endl;cin>>num;

fact = 1;for( i = 1; i<= num; i++)

fact = fact * i;cout<<” The factorial of a ”<<num<<”! is: “<<fact<<endl;getch( );

}Practical Program 16: Write a C++ program to generate the Fibonacci sequence up to a limit using

for statement. (Hint: 5 = 0 1 1 2 3)


int num, first, second, count, third;clrscr( );cout<<”Enter the number limit for Fibonacci Series”<<endl;cin>>num;first = 0;second = 1;cout<<first<<”\t”<<second;third = first + second;for( count = 2; third<=num; count++){

cout<<”\t”<<thirdfirst = second;second = third;third = first + second;

}cout<<”\n Total terms = “<<count<<endl;getch( );

}


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Jump statements or Transfer of control from within loop

Transfer of control within looping are used to

o Terminate the execution of loop.

o Exiting a loop.

o Half way through to skip the loop.

All these can be done by using break, exit and continue statements.

break statement

The break statement has two uses

o You can use it to terminate a case in the switch statement.

o You can also use it to force immediate termination of a loop like while, do-while and for, by

passing the normal loop conditional test.

When the break statement is encountered inside a loop, the loop is immediately terminated and

program control resumes at the next statement.

The general form of break statement is:

break;

Example:

for (n=0; n<100; n++){

cout<<n;if(n==10) break;

}Program: To test whether a given number is prime or not using break statement.

#include<iostream.h>#include,conio.h>void main( ){

int n, i, status;clrscr( );cout<<”Enter the number”;cin>>n;status=1;for(i=2; i<=n/2; i++){

if(n % i ==0){

status=0cout<<”It is not a prime”<<endl;break;


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}}if(status)cout<<”It is a prime number”<<endl;getch( );

} exit( ) function:

This function causes immediate termination of the entire program, forcing a return to the operating

system.

In effect, exit( ) function acts as if it were breaking out of the entire program.

The general form of the exit( ) function is:

exit( ); or void exit( int return_code);

The return code is used by the operating system and may be used by calling programs.

An exit code of 0 means that the program finished normally and any other value means that some

error or unexpected results happened.

Program: To test whether a given number is prime or not using exit( ) statement.

#include<iostream.h>#include,conio.h>void main( ){

int n, i;clrscr( );cout<<”Enter the number”;cin>>n;for(i=2; i<=n/2; i++){

if(n % i ==0){

cout<<”It is not a prime”<<endl;exit(0);

}}cout<<”It is a prime number”<<endl;getch( );

} continue statement:

The continue statement causes the program to skip the rest of the loop in the current iteration as if

end of the statement block has been reached, causing it to jump to start of the following iteration.

The continue statement works somewhat like break statement.


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Instead of forcing termination, however continue forces the next iteration of the loop to take place,

skipping any code in between.

The general form of the continue statement is:

continue;

Example:for (n=10; n<0; n--){

if(n==10) continue;cout<<n;

} goto statement:

The goto allows to makes an absolute jump to another point in the program.

This statement execution causes an unconditional jump or transfer of control from one statement to

the other statement with in a program ignoring any type of nesting limitations.

The destination is identified by a label, which is then used as an argument for the goto statement.

A label is made of a valid identifier followed by a colon (:).

The general form of goto statement is:

statement1;

statement2;

goto label_name;

statement 3;

statement4;

label_name: statement5;

statement6;

Program: To print from 10 to 1 using goto statements.

#include<iostream.h>#include<conio.h>#include<iomanip.h>void main( ){

int n=10;loop: cout<<”\t”<<n;n--;if(n>0) goto loop;cout<<”End of loop”;getch( );

}


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CHAPTER 10 – CONTROL STATEMENTS BLUE PRINT

VSA (1 marks) SA (2 marks) LA (3 Marks) Essay (5 Marks) Total

01 Question - - 02 Question 11 Marks

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