CONTROL FLOW STRUCTURES ( Decision making & Looping )

 CONTROL FLOW STRUCTURES

 order in which instructions are executed.

Categorized into three main types:

1.    1.  Sequential

2.     2. Conditional à a.  Decision making(selection)          b. Looping (iteration)

3.    3. Un-conditional (Jump) )à a. Goto     b. Break           c. Continue

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1. Sequential Control Flow

• default flowà: statements execution flowà one after the other.

 

Example:-

#include <iostream>

using namespace std;

 

int main() {

    cout << "This is sequential execution." << endl;

    cout << "Next statement executes." << endl;

    return 0;

}

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2. Selection Control Flow

• Used for decision-making (branching).

 

Types :-

a) simple if Statement

·       Executes a block of code if a condition is true.

 

Syntax:

if (condition) {

    // Code to execute if condition is true

}

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    int x = 10;

    if (x > 5) {

        cout << "x is greater than 5" << endl;

    }

    return 0;

}

 

b) if-else Statement

·       Provides an alternative block if the condition is false.

 

 

Syntax:

if (condition) {

    // Code if condition is true

} else {

    // Code if condition is false

}

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    int x = 3;

    if (x > 5) {

        cout << "x is greater than 5" << endl;

    } else {

        cout << "x is not greater than 5" << endl;

    }

    return 0;

}

 

c) if-else if-else Statement

·       Used for multiple conditions.

Syntax:

if (condition1) {

    // Code for condition1

} else if (condition2) {

    // Code for condition2

} else {

    // Code if none of the conditions are true

}

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    int x = 8;

    if (x > 10) {

        cout << "x is greater than 10" << endl;

    } else if (x > 5) {

        cout << "x is greater than 5 but less than or equal to 10" << endl;

    } else {

        cout << "x is 5 or less" << endl;

    }

    return 0;

}

 

d) switch Statement

Used for selecting among multiple options.

Syntax:

switch (variable) {

    case value1:

        // Code for case value1

        break;

    case value2:

        // Code for case value2

        break;

    default:

        // Code if no case matches

}

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    int day = 3;

    switch (day) {

        case 1:

            cout << "Monday" << endl;

            break;

        case 2:

            cout << "Tuesday" << endl;

            break;

        case 3:

            cout << "Wednesday" << endl;

            break;

        default:

            cout << "Invalid day" << endl;

    }

    return 0;

}

 

e. Nested-if

·       if statement inside another if statement.

Syntax: 

if (condition1)

{

   // Executes when condition1 is true

   if (condition2)

   {

      // Executes when condition2 is true

   }

}

 

Flowchart 

 

Example: 

#include <iostream>

using namespace std;

 

int main()

{

    int i = 10;

 

    if (i == 10) {

        // First if statement

        if (i < 15)

            cout << "i is smaller than 15\n";

 

        // Nested - if statement

        // Will only be executed if

        // statement above is true

        if (i < 12)

            cout << "i is smaller than 12 too\n";

        else

            cout << "i is greater than 15";

    }

return 0;

}

 

Output:

i is smaller than 15

i is smaller than 12 too

 

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3. Iteration (Loops)

·       Used to repeat a block of code.

 

Two Types :-

A.    entry controlled. à a. while loop.      b. for loop

B.    Exit controlled  à do…while loop

 

a) for Loop

·       Executes a block of code a specific number of times.

 

Syntax:

for (initialization; condition; increment/decrement) {

    // Code to execute

}

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    for (int i = 0; i < 5; i++) {

        cout << "i: " << i << endl;

    }

    return 0;

}

 

b) while Loop

·       Executes a block of code as long as the condition is true.

Syntax:

while (condition) {

    // Code to execute

}

 

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    int i = 0;

    while (i < 5) {

        cout << "i: " << i << endl;

        i++;

    }

    return 0;

}

 

c) do-while Loop

Executes the block of code at least once and then repeats while the condition is true.

 

Syntax:

do {

    // Code to execute

} while (condition);

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    int i = 0;

    do {

        cout << "i: " << i << endl;

        i++;

    } while (i < 5);

    return 0;

}

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4. Jump Statements

·       Control the flow by jumping to another part of the code.

 

a) break

·       Exits a loop or switch statement.

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    for (int i = 0; i < 5; i++) {

        if (i == 3) break;

        cout << "i: " << i << endl;

    }

    return 0;

}

 

b) continue

·       Skips the current iteration of the loop.

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    for (int i = 0; i < 5; i++) {

        if (i == 2) continue;

        cout << "i: " << i << endl;

    }

    return 0;

}

 

c) goto

·       Transfers control to a labeled statement.

 

Example:

#include <iostream>

using namespace std;

 

int main() {

    int x = 1;

    if (x == 1) goto label;

    cout << "This won't execute" << endl;

 

label:

    cout << "Jumped to label" << endl;

    return 0;

}

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