Console.WriteLine(7 > 3);
Console.WriteLine(7 < 3);

True
False

int score = 85;
bool passed = score >= 60;

Console.WriteLine($"Score: {score}");
Console.WriteLine($"Passed: {passed}");

Score: 85
Passed: True

int a = 5;

a = 7;                      // assignment: put 7 into a
Console.WriteLine(a == 7);  // comparison: is a equal to 7?

True

bool check = temperature = 50;

1-11-weather.cs(11,26): error CS0029: Cannot implicitly convert type 'int' to 'bool'
The build failed. Fix the build errors and run again.

Console.Write("In open water? (true/false) ");
bool openWater = bool.Parse(Console.ReadLine());

Console.WriteLine($"Open water: {openWater}");

In open water? (true/false) true [Enter]
Open water: True

In open water? (true/false) yes [Enter]
Unhandled exception. System.FormatException: String 'yes' was not recognized as a valid Boolean.
   at System.Boolean.Parse(String value)
   at Program.<Main>$(String[] args) in 1-11-weather.cs:line 29

string windSpeed = Console.ReadLine();

bool highWind = windSpeed >= 40;

1-11-weather.cs(21,17): error CS0019: Operator '>=' cannot be applied to operands of type 'string' and 'int'
The build failed. Fix the build errors and run again.

'F' → Fullscreen

Build

Everything today goes in a new program named 1-11-weather.

Task 1: Compare Directly

• Write the code below and run it.
• Both comparisons sit inside the interpolation braces. That is allowed — a comparison is a value like any other, so it can go anywhere a value can.
• Change the temperature to a negative number and run it again. Write down which of the two lines changed and which did not.
• Both lines still print. A comparison produces a value; it does not stop anything.

1
int temperature = 31;
2

3
Console.WriteLine($"Temperature: {temperature}");
4
Console.WriteLine($"Above freezing: {temperature > 0}");
5
Console.WriteLine($"Below boiling: {temperature < 100}");

Task 2: Store the Answers

• Add a humidity reading and three named boolean variables.
• Note the names: each one reads like a yes-or-no question about the data.
• Each is declared bool — the fourth type from Activity 1.5. You typed those by hand. These are produced by the comparison on the right of the =.
• isExactlyFreezing uses two equals signs. One would mean something completely different, and Task 4 shows you exactly what.

1
int temperature = 31;
2
int humidity = 82;
3

4
Console.WriteLine($"Temperature: {temperature}");
5
Console.WriteLine($"Above freezing: {temperature > 0}");
6
Console.WriteLine($"Below boiling: {temperature < 100}");
7
Console.WriteLine();
8

9
bool isHot = temperature >= 30;
10
bool isHumid = humidity >= 70;
11
bool isExactlyFreezing = temperature == 0;
12

13
Console.WriteLine($"Hot: {isHot}");
14
Console.WriteLine($"Humid: {isHumid}");
15
Console.WriteLine($"Exactly freezing: {isExactlyFreezing}");

Task 3: Plan, Then Compare Some Input

• The comments describe a wind-speed check. Write the code under them.
• Convert the wind speed before you compare it. Task 4 shows what happens if you forget.
• “NOT exactly zero” is one comparison, not two. Look back at the six operators.
• The open-water answer is already true or false, so it needs bool.Parse rather than int.Parse. The user has to type true or false, which is why the prompt says so.

1
int temperature = 31;
2
int humidity = 82;
3

4
Console.WriteLine($"Temperature: {temperature}");
5
Console.WriteLine($"Above freezing: {temperature > 0}");
6
Console.WriteLine($"Below boiling: {temperature < 100}");
7
Console.WriteLine();
8

9
bool isHot = temperature >= 30;
10
bool isHumid = humidity >= 70;
11
bool isExactlyFreezing = temperature == 0;
12

13
Console.WriteLine($"Hot: {isHot}");
14
Console.WriteLine($"Humid: {isHumid}");
15
Console.WriteLine($"Exactly freezing: {isExactlyFreezing}");
16
Console.WriteLine();
17

18
// Ask the user for a wind speed and convert it to a whole number
19
// Store whether the wind is at or above 40
20
// Store whether the wind is NOT exactly zero
21
// Display both results with labels
22

23
// Ask whether the boat is in open water
24
// That answer is already true or false, so use bool.Parse
25
// Display that answer with a label

Task 4: Break It on Purpose

Three runs of your finished program. Write down exactly what happens each time, copied from the screen, and change each one back before the next.

1. Run it normally, and type yes when it asks about open water.
2. Change isExactlyFreezing to use a single equals sign. Try to run it.
3. Store the wind speed as a string instead: change int to string and remove the int.Parse(...) wrapper, keeping Console.ReadLine(). Try to run it.

For each one, record the error code — something like CS0029 — or the exception name, and the line number it names.

Two of these never ran at all. One ran, then stopped. Say which is which, and how you can tell from the screen.

Challenge (Optional): The Comparison C# Made You Ask For

• Task 4's third break refused to compare text to a number. But text can be put in order — C# just will not do it by accident.
• Add this line and run it: Console.WriteLine(string.Compare("9", "100") > 0);
• Write a comment explaining what that answered, and why comparing "9" and "100" as text gives that result when comparing 9 and 100 as numbers would not.

Same Idea, Exam Notation

int score = 85;
bool passed = score >= 60;
bool perfect = score == 100;
bool failed = score != 100;

score ← 85
passed ← score ≥ 60
perfect ← score = 100
failed ← score ≠ 100

This is the panel where the two notations disagree most. Read the middle row carefully.

A single = means assignment in C# and equality on the exam. The same character, two opposite jobs, depending on which notation you are reading.

Because the exam uses ← for assignment, there is no ambiguity within the notation — the confusion only happens when you switch between the two. When you see score = 100 on an exam question, it is asking a question, not setting a value.

Checkpoint

Your finished program should run like this.

Temperature: 31
Above freezing: True
Below boiling: True

Hot: True
Humid: True
Exactly freezing: False

Wind speed? 12 [Enter]
High wind: False
Wind is moving: True

In open water? (true/false) true [Enter]
Open water: True

• Every boolean prints True or False, with a capital letter.
• The three Task 2 booleans are stored in variables; the two Task 1 comparisons are not.
• A wind speed of 12 gives False for high wind and True for moving.
• You have the negative-temperature result from Task 1 written down.
• All three Task 4 results are written down, with error codes or exception names and their line numbers.

Reflection

Answer the following questions before submitting your work.

1. passed stores the answer to a question rather than a number. Why is that more useful than storing the score again?
2. Explain the difference between = and == in C#, as if to someone who has never programmed. Then describe a mistake you could make by forgetting that a single = means “is equal to” on the exam.
3. Two of Task 4's three breaks were refused before the program ran. One was not. Which one, and why is that the more dangerous kind?

Submit

Submit five things to the dropbox:

1. Your 1-11-weather program file.
2. A copy of one full run with a wind speed of 12 and open water true.
3. Your Task 1 negative-temperature result.
4. Your three Task 4 results, with error codes or exception names and line numbers, and which one ran before it stopped.
5. Your three reflection answers.

Activity Complete