Select Case

As you have seen from the If…Elseif…Elseif…Else statement, when there are many choices, the structure can be hard to follow. Some programming languages have an alternative structure when this happens. The Select Case or Switch Case statement is also a decision structure that is sometimes preferred because code might be easier to read and understand, by people.

The Select Case structure takes a variable and then compares it to a list of expressions. The first expressions that is evaluated as, “True” is executed and the remaining of the select case structure is skipped over, just like an If…ElseIf… statement (but not in all languages!). There are several different ways to create your expression. You can just use a value (a single digit for example and then it does an equal comparison), several digits, a range or having a regular expression. Just like the If structure, there is an optional “Else” that can be placed at the end as a catch all. The general form of a Select…Case statement (in most computer programming languages), takes the generic form of:

SELECT (variable)

CASE valueOne

//statements

CASE valueTwo

//statements

CASE valueThree

//statements

…

ELSE //optional

//statements

In this example program, the user enters in a grade letter. The letter grades are A, B, C, D & F. The computer will tell you if you are doing well, average or poorly. If the user enters in a grade that is not A, B, C, D or F, the computer will tell you that you have entered in an invalid grade.

Top-Down Design for Select Case statement

Flowchart for Select Case statement

Pseudocode for Select Case statement

GET grade

SELECT (grade)

CASE “A”

SHOW “Excellent!”

CASE “B”

SHOW “Good job!”

CASE “C”

SHOW “Average.”

CASE “D”

SHOW “Poor.”

CASE “F”

SHOW “Fail.”

ELSE

SHOW “Invalid grade.”

Code for Select Case statement

C

C++

C#

Go

Java

JavaScript

Python

// Copyright (c) 2020 Mr. Coxall All rights reserved.
//
// Created by: Mr. Coxall
// Created on: Sep 2020
// This program checks your grade

#include <stdio.h>
#include <ctype.h>

int main() {
    // this function checks your grade
    char gradeLevel;  // a single character

    // input
    printf("Enter grade mark as a single character(ex: A, B, ...): ");
    scanf("%c", &gradeLevel);

    // process and output
    // Note you need the break in C or it will move to next
    // line in switch statement if it is true again
    switch (toupper(gradeLevel)) {
        case 'A':
            printf("Excellent!\n");
            break;
        case 'B':
            printf("Good job!\n");
            break;
        case 'C':
            printf("Average.\n");
            break;
        case 'D':
            printf("Poor.\n");
            break;
        case 'F':
            printf("Fail.\n");
            break;
        default:
            printf("Invalid grade.\n");
    }

    printf("\nDone.\n");
    return 0;
}

// Copyright (c) 2020 St. Mother Teresa HS All rights reserved.
//
// Created by: Mr. Coxall
// Created on: Sep 2020
// This program checks your grade

#include <iostream>
#include <cctype>

int main() {
    // this function checks your grade
    char gradeLevel;  // a single character

    // input
    std::cout << "Enter grade mark as a single character(ex: A, B, ...): ";
    std::cin >> gradeLevel;

    // process and output
    // switch in C++ can not support strings, only numbers and char
    // also note you need the break in C++ or it will move to next
    // line in switch statement if it is true again
    switch (toupper(gradeLevel)) {
        case 'A':
            std::cout << "Excellent!" << std::endl;
            break;
        case 'B':
            std::cout << "Good job!" << std::endl;
            break;
        case 'C':
            std::cout << "Average." << std::endl;
            break;
        case 'D':
            std::cout << "Poor." << std::endl;
            break;
        case 'F':
            std::cout << "Fail." << std::endl;
            break;
        default:
            std::cout << "Invalid grade." << std::endl;
    }

    std::cout << "\nDone." << std::endl;
}

/* Created by: Mr. Coxall
 * Created on: Sep 2020
 * This program checks a student's grade
*/

using System;

/*
 * The Program class
*/
class Program {
    static void Main() {
        // this function checks a student's grade

        // create Scanner object for user input
        Console.Write("Enter your grade: ");
        string grade = Console.ReadLine();

        // process & output
        switch (grade.ToUpper()) {
            case "A":
                Console.WriteLine("Excellent!");
                break;
            case "B":
                Console.WriteLine("Good job!");
                break;
            case "C":
                Console.WriteLine("Average.");
                break;
            case "D":
                Console.WriteLine("Poor.");
                break;
            case "F":
                Console.WriteLine("Fail.");
                break;
            default:
                Console.WriteLine("Invalid grade.");
                break;
        }

        Console.WriteLine("\nDone.");
    }
}

/**
 * Created by: Mr. Coxall
 * Created on: Sep 2020
 * This program checks a student's grade
 */

package main

import (
	"fmt"
	"strings"
)

func main() {
	// this function checks a student's grade

	var grade string

	// input
	fmt.Print("Enter your grade: ")
	fmt.Scanln(&grade)

	// process and output
	switch strings.ToUpper(grade) {
		case "A":
			fmt.Println("Excellent!")
		case "B":
			fmt.Println("Good job!")
		case "C":
			fmt.Println("Average.")
		case "D":
			fmt.Println("Poor.")
		case "F":
			fmt.Println("Fail.")
		default:
			fmt.Println("Invalid grade.")
	}

	fmt.Println("\nDone.")
}

/*
 * This program checks a student's grade
 *
 * @author  Mr Coxall
 * @version 1.0
 * @since   2020-09-01
 */

import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    // this function checks a traffic light

    // create Scanner object for user input
    Scanner scanner = new Scanner(System.in);

    // input
    System.out.print("Enter your grade: ");
    String grade = scanner.nextLine();

    // process & output
    switch (grade.toUpperCase()) {
      case "A":
        System.out.println("Excellent!");
        break;
      case "B":
        System.out.println("Good job!");
        break;
      case "C":
        System.out.println("Average.");
        break;
      case "D":
        System.out.println("Poor.");
        break;
      case "F":
        System.out.println("Fail.");
        break;
      default:
        System.out.println("Invalid grade.");
        break;
    }

    // close the Scanner object
    scanner.close();
    System.out.println("\nDone.");
  }
}

/* Created by: Mr. Coxall
 * Created on: Sep 2020
 * This program checks a student's grade
 */

const prompt = require("prompt-sync")()

// input
const grade = prompt("Enter your grade: ")

// process & output
switch (grade.toUpperCase()) {
  case "A":
    console.log("Excellent!")
    break
  case "B":
    console.log("Good job!")
    break
  case "C":
    console.log("Average.")
    break
  case "D":
    console.log("Poor.")
    break
  case "F":
    console.log("Fail.")
    break
  default:
    console.log("Invalid grade.")
    break
}

console.log("\nDone.")

#!/usr/bin/env python3
"""
Created by: Mr. Coxall
Created on: Sep 2020
This module checks a student's grade
"""


def main() -> None:
    """The main() function checks a student's grade, returns None."""

    # input
    grade = input("Enter grade mark as a single character(ex: A, B, ...): ")

    # process & output
    # NOTE: This will only work on >= Python 3.10
    match grade.upper():
        case "A":
            print("Excellent!")
        case "B":
            print("Good job!")
        case "C":
            print("Average.")
        case "D":
            print("Poor.")
        case "F":
            print("Fail.")
        case _:
            print("Invalid grade.")

    print("\nDone.")


if __name__ == "__main__":
    main()

Example Output