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Understanding If-Else Statements in Programming: A Comprehensive Guide

This guide explores the concept of if-else statements in programming, which allow developers to implement decision-making in their code. By using an if-else structure, a program can follow different paths based on the evaluation of conditions. We’ll provide examples, such as temperature checks and grading systems, to illustrate how these statements work. Additionally, we'll discuss the importance of validating inputs, handling errors, and improving code clarity with proper indentation and organization.

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Understanding If-Else Statements in Programming: A Comprehensive Guide

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  1. If-Else Statement

  2. Review • So far… • Input • Output • Remember and • Modify data • Yet to come… • Decision branching • Looping

  3. The if-else Statement if (expression)    statement1else    statement2 allows a program to take one of two branches or paths of execution depending on the value of some expression

  4. The if-else Statement if (expression)    statement1else    statement2 allows a program to take one of two branches or paths of execution depending on the value of some expression

  5. The if-else Statement if (expression)    statement1else    statement2 allows a program to take one of two branches or paths of execution depending on the value of some expression

  6. The if-else Statement if (expression)    statement1else    statement2 allows a program to take one of two branches or paths of execution depending on the value of some expression

  7. Warning! if (temperature > 100); {cout << “It’s hot outside”; }

  8. Example #1 if (4) cout << “hello”;

  9. Example #2 if (0) cout << “hello”;

  10. Example #3 cout << “enter radius: “; cin >> radius; if (radius <= 0) { cout << “Error: no circle has non-positive radius!” << endl; exit(1); }area = PI * radius * radius; cout << “The circle with radius ” << radius << “ has area ” << area << “.” << endl;cout << “Ending this example...” << endl;

  11. Example #3 (revisited) cout << “enter radius: “; cin >> radius; if (radius <= 0) cout << “Error: no circle has non-positive radius!” << endl;else{    area = PI * radius * radius; cout << “The circle with radius ” << radius << “ has area ” << area << “.” << endl;} cout << “Ending this example...” << endl;

  12. Tabs vs Spaces if (tabs == true) {cout << “This is”; cout << “ an example”; cout << “ of bad”; cout << “indentation.”;cout << endl;}

  13. const int MAX_A = 100;const int MIN_A = 90;const int MIN_B = 80; cout << “enter average: ”;cin >> ave;if (ave > MAX_A)cout << “Error: average out of range!” << endl;else    if (ave >= MIN_A)        grade = ‘A’;    else        if (ave >= MIN_B)            grade = ‘B’;        else            if (ave >= MIN_C)                grade = ‘C’;            else                grade = ‘F’;

  14. const int MAX_A = 100;const int MIN_A = 90;const int MIN_B = 80; cout << “enter average: ”;cin >> ave;if (ave > MAX_A)cout << “Error: average out of range!” << endl;else    if (ave >= MIN_A)        grade = ‘A’;    else        if (ave >= MIN_B)            grade = ‘B’;        else            if (ave >= MIN_C)                grade = ‘C’;            else                grade = ‘F’;

  15. const int MAX_A = 100;const int MIN_A = 90;const int MIN_B = 80; cout << “enter average: ”;cin >> ave;if (ave > MAX_A)cout << “Error: average out of range!” << endl;else    if (ave >= MIN_A)        grade = ‘A’;    else        if (ave >= MIN_B)            grade = ‘B’;        else            if (ave >= MIN_C)                grade = ‘C’;            else                grade = ‘F’;

  16. const int MAX_A = 100;const int MIN_A = 90;const int MIN_B = 80; cout << “enter average: ”;cin >> ave;if (ave > MAX_A)cout << “Error: average out of range!” << endl;else    if (ave >= MIN_A)        grade = ‘A’;    else        if (ave >= MIN_B)            grade = ‘B’;        else            if (ave >= MIN_C)                grade = ‘C’;            else                grade = ‘F’;

  17. const int MAX_A = 100;const int MIN_A = 90;const int MIN_B = 80; cout << “enter average: ”;cin >> ave;if (ave > MAX_A)cout << “Error: average out of range!” << endl;else    if (ave >= MIN_A)        grade = ‘A’;    else        if (ave >= MIN_B)            grade = ‘B’;        else            if (ave >= MIN_C)                grade = ‘C’;            else                grade = ‘F’;

  18. cin >> ave;if (ave > MAX_A)cout << “Error: average out of range!” << endl;else if (ave >= MIN_A)    grade = ‘A’;else if (ave >= MIN_B)    grade = ‘B’;else if (ave >= MIN_C)    grade = ‘C’;else if (ave >= MIN_D)    grade = ‘D’;else if (ave >= 0)    grade = ‘F’;else    exit(3);

  19. The exit Function return 0; exit (3);

  20. End of Session

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