Getting into the Program Flow — Programming Examples

Example 1 — Validate a Course Score with Nested Decisions

An outer if rejects scores outside 0–100 before an inner if decides whether a valid score passes. The nested blocks keep the passing decision from running on invalid data.

using System;

class Program
{
    static void Main()
    {
        const int PassingScore = 70;
        int score = 86;
        bool completedFinal = true;

        if (score < 0 || score > 100)
        {
            Console.WriteLine("Score must be between 0 and 100.");
        }
        else
        {
            if (score >= PassingScore && completedFinal)
            {
                Console.WriteLine("Passed the course.");
            }
            else
            {
                Console.WriteLine("Course requirements are not complete.");
            }
        }
    }
}

Example 2 — Classify Enrollment with Two Switch Forms

A switch statement selects a message for a course track, with two labels sharing one action. A switch expression then uses relational patterns and a _ fallback to classify credit hours.

using System;

class Program
{
    static void Main()
    {
        string track = "Web";
        int creditHours = 9;

        switch (track)
        {
            case "Web":
            case "App":
                Console.WriteLine("Software development track");
                break;
            case "Network":
                Console.WriteLine("Network technology track");
                break;
            default:
                Console.WriteLine("Unknown track");
                break;
        }

        string enrollment = creditHours switch
        {
            >= 12 => "full-time",
            >= 6 and < 12 => "half-time",
            >= 1 and < 6 => "less than half-time",
            _ => "not enrolled"
        };

        Console.WriteLine("Enrollment: " + enrollment);
    }
}

Example 3 — Keep Asking for a Valid Exam Score

The while (true) loop retries invalid input. continue skips the remaining work on an invalid attempt, while break exits once the student enters a score from 0 through 100.

using System;

class Program
{
    static void Main()
    {
        while (true)
        {
            Console.Write("Enter exam score (0-100): ");
            string input = Console.ReadLine() ?? "";

            if (!int.TryParse(input, out int score) || score < 0 || score > 100)
            {
                Console.WriteLine("Enter a whole number from 0 through 100.");
                continue;
            }

            Console.WriteLine("Recorded score: " + score);
            break;
        }
    }
}

Example 4 — Record Sales with a Do-While Loop

The sales prompt must appear at least once, so this program uses do…while and asks whether to record another sale after each entry. A valid amount adds to the running total; an invalid amount leaves it unchanged.

using System;

class Program
{
    static void Main()
    {
        decimal total = 0m;
        int saleCount = 0;
        string again;

        do
        {
            Console.Write("Sale amount: ");
            string input = Console.ReadLine() ?? "";

            if (decimal.TryParse(input, out decimal sale) && sale >= 0m)
            {
                total += sale;
                saleCount++;
            }
            else
            {
                Console.WriteLine("Enter a nonnegative amount.");
            }

            Console.Write("Record another sale? (y/n): ");
            again = (Console.ReadLine() ?? "n").Trim().ToLower();
        } while (again == "y");

        Console.WriteLine("Sales recorded: " + saleCount);
        Console.WriteLine("Total: $" + total.ToString("F2"));
    }
}

Example 5 — Print an Exam Seating Plan with Nested For Loops

The outer for loop moves through rows while the inner loop prints seat labels. A break closes only the current row when a blocked seat is reached; openSeats lives outside both loops so the final count remains available.

using System;

class Program
{
    static void Main()
    {
        int openSeats = 0;

        for (int row = 1; row <= 3; row++)
        {
            Console.Write("Row " + row + ":");

            for (int seat = 1; seat <= 4; seat++)
            {
                if (row == 2 && seat == 3)
                {
                    Console.Write(" [row closed]");
                    break;
                }

                string label = row + "-" + seat;
                Console.Write(" " + label);
                openSeats++;
            }

            Console.WriteLine();
        }

        Console.WriteLine("Open seats: " + openSeats);
    }
}