Conditionals

Overview

Definition

Conditional statements are essential programming constructs that allow us to make decisions based on certain conditions. These statements evaluate an expression and execute specific code blocks based on whether the condition is true or false. The most common conditional statements are if, else if, else, nested if, and switch.

Use Cases

Decision-making

Executing different code based on specific conditions.

Input Validation

Checking user input for validity before processing it.

Flow Control

Controlling program flow based on conditions.

Error Handling

Handling specific error conditions.

Menu Selection

Implementing menu-driven applications.

Pros & Cons

👍

Improved Control

Allows the program to make dynamic decisions during runtime.

Readable Code

Conditional statements enhance code readability by expressing intent clearly.

Saves Resources

Prevents unnecessary execution of code, optimizing resource utilization.

👎

Complexity

Multiple nested conditions can make code harder to maintain and understand.

Code Duplication

Repeating code blocks for similar conditions can lead to code duplication.

Potential Bugs

Incorrect conditions or missing cases can introduce bugs.

if, else if, else Syntax

Pseudocode

C++

#include <iostream>
using namespace std;

int main() {
    int exam_score;
    int passing_threshold = 60;

    cout << "Enter your exam score: ";
    cin >> exam_score;

    if (exam_score >= passing_threshold) {
        cout << "Congratulations! You passed the exam." << endl;
    } else {
        cout << "Unfortunately, you did not pass the exam. Please try again." << endl;
    }

    return 0;
}

Python

passing_threshold = 60

exam_score = int(input("Enter your exam score: "))

if exam_score >= passing_threshold:
    print("Congratulations! You passed the exam.")
else:
    print("Unfortunately, you did not pass the exam. Please try again.")

Java

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int passing_threshold = 60;

        System.out.print("Enter your exam score: ");
        int exam_score = scanner.nextInt();

        if (exam_score >= passing_threshold) {
            System.out.println("Congratulations! You passed the exam.");
        } else {
            System.out.println("Unfortunately, you did not pass the exam. Please try again.");
        }
    }
}

Rust

use std::io;

fn main() {
    let passing_threshold = 60;

    println!("Enter your exam score: ");
    let mut input = String::new();
    io::stdin().read_line(&mut input).expect("Failed to read line");
    let exam_score: i32 = input.trim().parse().expect("Please enter a valid number");

    if exam_score >= passing_threshold {
        println!("Congratulations! You passed the exam.");
    } else {
        println!("Unfortunately, you did not pass the exam. Please try again.");
    }
}

Golang

package main

import (
    "fmt"
)

func main() {
    var passing_threshold int = 60
    var exam_score int

    fmt.Print("Enter your exam score: ")
    fmt.Scan(&exam_score)

    if exam_score >= passing_threshold {
        fmt.Println("Congratulations! You passed the exam.")
    } else {
        fmt.Println("Unfortunately, you did not pass the exam. Please try again.")
    }
}

Output

We prompt the user to enter their exam score and compare it with the passing_threshold value of 60. If the exam_score is greater than or equal to 60, the program outputs a success message indicating that the student passed the exam. Otherwise, it prints a message stating that the student did not pass and should try again.

Assume the user enters 75 as input for all the examples.

Since the input 75 is greater than the passing threshold of 60, the output is: `Congratulations! You passed the exam.``.

Congratulations! You passed the exam.

switch / match Syntax

Pseudocode

FUNCTION name_of_function (parameter1, parameter2, ...):
    // Function implementation here
    RETURN result

C++

Rules of Use :

#include <iostream>
using namespace std;

int main() {
    int day_number;

    cout << "Enter a day number (1 to 7): ";
    cin >> day_number;

    switch (day_number) {
        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. Please enter a number between 1 and 7." << endl;
            break;
    }

    return 0;
}

Python

Rules of Use :

day_number = int(input("Enter a day number (1 to 7): "))

if day_number == 1:
    print("Sunday")
elif day_number == 2:
    print("Monday")
elif day_number == 3:
    print("Tuesday")
elif day_number == 4:
    print("Wednesday")
elif day_number == 5:
    print("Thursday")
elif day_number == 6:
    print("Friday")
elif day_number == 7:
    print("Saturday")
else:
    print("Invalid day number. Please enter a number between 1 and 7.")

Java

Rules of Use :

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int day_number;

        System.out.print("Enter a day number (1 to 7): ");
        day_number = scanner.nextInt();

        switch (day_number) {
            case 1:
                System.out.println("Sunday");
                break;
            case 2:
                System.out.println("Monday");
                break;
            case 3:
                System.out.println("Tuesday");
                break;
            case 4:
                System.out.println("Wednesday");
                break;
            case 5:
                System.out.println("Thursday");
                break;
            case 6:
                System.out.println("Friday");
                break;
            case 7:
                System.out.println("Saturday");
                break;
            default:
                System.out.println("Invalid day number. Please enter a number between 1 and 7.");
                break;
        }
    }
}

Rust

Rules of Use :

use std::io;

fn main() {
    let mut day_number = String::new();

    println!("Enter a day number (1 to 7): ");
    io::stdin().read_line(&mut day_number).expect("Failed to read line");
    let day_number: i32 = day_number.trim().parse().expect("Please enter a valid number");

    match day_number {
        1 => println!("Sunday"),
        2 => println!("Monday"),
        3 => println!("Tuesday"),
        4 => println!("Wednesday"),
        5 => println!("Thursday"),
        6 => println!("Friday"),
        7 => println!("Saturday"),
        _ => println!("Invalid day number. Please enter a number between 1 and 7."),
    }
}

Golang

Rules of Use :

package main

import (
    "fmt"
)

func main() {
    var day_number int

    fmt.Print("Enter a day number (1 to 7): ")
    fmt.Scan(&day_number)

    switch day_number {
    case 1:
        fmt.Println("Sunday")
    case 2:
        fmt.Println("Monday")
    case 3:
        fmt.Println("Tuesday")
    case 4:
        fmt.Println("Wednesday")
    case 5:
        fmt.Println("Thursday")
    case 6:
        fmt.Println("Friday")
    case 7:
        fmt.Println("Saturday")
    default:
        fmt.Println("Invalid day number. Please enter a number between 1 and 7.")
    }
}

Output

We take a user input for the day_number and use a switch statement (or if-elif statements in Python) to display the corresponding day of the week. Assuming the user input is 3, the output for each program is Tuesday.

Tuesday