Control Structures in CPP

 Control Structures

 Control Structures are just a way to specify flow of control in programs.

  There are three basic types of flow of control, known as:

• Sequence logic, or sequential flow

• Selection logic, or conditional flow

• Iteration logic, or repetitive flow

Sequence Logic

Sequential logic as the name suggests follows a serial or sequential flow in which the flow depends on the series of instructions given to the computer. 

Selection Logic (Branching)

Selection Logic simply involves a number of conditions which decides one out of several written statements.

Iteration Logic (Looping)

It helps to repeat a statement a certain number of times until the condition is satisfied. 

Selection Logic (Branching)

Selection Logic simply involves a number of conditions which decides one out of several written statements.

• If statement

• If…else statement

• If… else if statement

• switch statement

 

if statement

« Use the if statement to specify a block of C++ code to be executed if

a condition is true.

Syntax

if (condition)

{

// block of code to be executed if the condition is true

) |

Example

#include <iostream.h>

void main()

{

if (20 > 18) {

cout << "20 is greater than 18";

)

)

#include<iostream>

using namespace std;

int main() {

    int a = 10, b = 20;

    if(a>b)

        cout<<"A is greater";

}

If...else statement

   - Use the if statement to specify a block of  C++ code to be executed

    if a condition is true.   

    Syntax   

    if

    (condition)  

    { // block of code to  be executed if the condition is true)  

    }

else{

//block of code to be executed}

Example – if…else

int a = 20;
if (a < 18)

 {
  cout << "Good day.";
} 

else

 {
  cout << "Good evening.";
} 

Output:

Good evening

#include<iostream>

using namespace std;

int main()

{

    int age;

    cout<<"Enter the age : ";

    cin>>age;

   

    if(age>=18)

        cout<<"You're eligible to vote";

       

    else

    cout<<"you are not eligible";

}

If... else if statement

« Use the if statement to specify a block of C++ code to be executed if a condition

is true.

« Use the else statement to specify a block of code to be executed if the condition

is false.

Syntax

if (condition)

{

// block of code to be executed if the condition is true

}

else if(Condition)

{

// block of code to be executed if the condition is false

}

else{

//block of code;

}

Example

int a = 22;
if (a < 10)

 {
  cout << "Good morning.";
}

 else if (a < 20) 

{
  cout << "Good day.";
} 

else

 {
  cout << "Good evening.";
}

Output

Good Evening

#include<iostream>

using namespace std;

int main() {

    int mark;

    cout<<"Enter the mark : ";

    cin>>mark;

    if(mark>=100 && mark >=90)

        cout<<"Your grade is A+";

    else if(mark>= 80 && mark<90)

        cout<<"your grade is A";

    else if(mark >=70 && mark <80)

        cout<<"your grade is B+";

    else if(mark >=60 && mark < 70)

        cout<<"your Grade is B";

    else if(mark >=50 && mark < 60)

        cout<<"your Grade is C";

    else if(mark>=45 && mark<50)

        cout<<"your grade is D";

    else

        cout<<"you are fail";

    return 0;

}

Switch Statement

Use the switch statement to select one of many code blocks to be executed.

Syntax:

switch(expression)

 {
  case x:
    // code block
    break;
  case y:
    // code block
    break;
  default:
    // code block

}

This is how it works:

The switch expression is evaluated once

The value of the expression is compared with the values of each case

If there is a match, the associated block of code is executed

Example:

int day = 4;

switch (day) {

case 1:

cout << "Monday";

break;

case 2:

cout << "Tuesday";

break;

case 3:

cout << "Wednesday";

break;

case 4:

cout << "Thursday":

break;

case 5:

cout << "Friday"; 

break;

case 6:

cout << "Saturday"; 

break;

case 7:

cout << "Sunday";

)

Output: Thursday