int oxygen = 88;
int coolant = 18;
int power = 132;

bool anyLow = oxygen < 25 || coolant < 25 || power < 25;

Console.WriteLine($"Any system low: {anyLow}");

Any system low: True

bool allFine = oxygen >= 25 && coolant >= 25 && power >= 25;

Console.WriteLine($"All systems fine: {allFine}");

All systems fine: False

bool isWeekend = false;

if (!isWeekend)
{
    Console.WriteLine("Go to school.");
}

Go to school.

int age = 16;
bool hasPermit = true;

if (age >= 16 && hasPermit)
{
    Console.WriteLine("May drive.");
}
else
{
    Console.WriteLine("May not drive.");
}

May drive.

int day = 3;

if (day == 6 || 7)
{
    Console.WriteLine("Weekend!");
}

1-15-systems.cs(3,5): error CS0019: Operator '||' cannot be applied to operands of type 'bool' and 'int'
The build failed. Fix the build errors and run again.

int oxygen = 18;
int coolant = 88;
int power = 132;

bool a = oxygen < 25 || coolant < 25 && power < 25;
bool b = (oxygen < 25 || coolant < 25) && power < 25;

Console.WriteLine($"a is {a}");
Console.WriteLine($"b is {b}");

a is True
b is False

'F' → Fullscreen

Build

Everything today goes in a new program named 1-15-systems.

Task 1: Three Readings, Two Answers

• Write the code below and run it.
• Only the coolant is low, and that is enough to make anyLow true and allFine false. Make sure you can say why for both.
• Now set all three readings above 25 and run it again. Write down all three printed values.
• Set the coolant back to 18 before you continue.

1
int oxygen = 88;
2
int coolant = 18;
3
int power = 132;
4

5
bool anyLow = oxygen < 25 || coolant < 25 || power < 25;
6
bool allFine = oxygen >= 25 && coolant >= 25 && power >= 25;
7

8
Console.WriteLine($"Any system low: {anyLow}");
9
Console.WriteLine($"All systems fine: {allFine}");
10
Console.WriteLine($"Not all fine: {!allFine}");

Task 2: Put Them to Work

• Add two decisions. The first uses a boolean you already stored; the second combines two comparisons on the spot.
• Both are valid. Storing the answer first is better when you need it more than once or the name explains something; combining inline is fine for a one-off.
• Find readings that give “STATUS: nominal” and “Short trips only” at the same time. Write them down. It is possible, and working out how is the task.

1
int oxygen = 88;
2
int coolant = 18;
3
int power = 132;
4

5
bool anyLow = oxygen < 25 || coolant < 25 || power < 25;
6
bool allFine = oxygen >= 25 && coolant >= 25 && power >= 25;
7

8
Console.WriteLine($"Any system low: {anyLow}");
9
Console.WriteLine($"All systems fine: {allFine}");
10
Console.WriteLine($"Not all fine: {!allFine}");
11
Console.WriteLine();
12

13
if (anyLow)
14
{
15
    Console.WriteLine("STATUS: attention required");
16
}
17
else
18
{
19
    Console.WriteLine("STATUS: nominal");
20
}
21

22
if (oxygen >= 25 && power >= 130)
23
{
24
    Console.WriteLine("Cleared for long haul.");
25
}
26
else
27
{
28
    Console.WriteLine("Short trips only.");
29
}

Task 3: Plan, Then Decide on Two Inputs

• The four comments describe a launch check. Write the code under them, leaving the comments where they are.
• Store the two answers in named booleans first, then combine them. The names are the point — a reader should not have to work out what crewSize >= 2 was for.
• Test all four combinations: both good, crew bad, mass bad, both bad. Only one of the four should approve.
• Then try exactly 2 crew and exactly 499 mass, and say whether your boundaries are the ones you meant.

1
int oxygen = 88;
2
int coolant = 18;
3
int power = 132;
4

5
bool anyLow = oxygen < 25 || coolant < 25 || power < 25;
6
bool allFine = oxygen >= 25 && coolant >= 25 && power >= 25;
7

8
Console.WriteLine($"Any system low: {anyLow}");
9
Console.WriteLine($"All systems fine: {allFine}");
10
Console.WriteLine($"Not all fine: {!allFine}");
11
Console.WriteLine();
12

13
if (anyLow)
14
{
15
    Console.WriteLine("STATUS: attention required");
16
}
17
else
18
{
19
    Console.WriteLine("STATUS: nominal");
20
}
21

22
if (oxygen >= 25 && power >= 130)
23
{
24
    Console.WriteLine("Cleared for long haul.");
25
}
26
else
27
{
28
    Console.WriteLine("Short trips only.");
29
}
30

31
Console.WriteLine();
32

33
// Ask for a crew size and convert it
34
// Ask for a cargo mass and convert it
35
// Store whether the crew is at least 2, and whether the mass is under 500
36
// A launch is allowed only if both are true -- approve it, or deny it

Task 4: Break It on Purpose

Two changes, one at a time. Write down exactly what happens, and put each back before the next.

1. In your launch check, replace massOk with cargoMass < 500 || 2. Try to run it.
2. Put it back. Now change anyLow to read oxygen < 25 || coolant < 25 && power < 25 — no parentheses — and run it with oxygen 18, coolant 88, power 132.

For each one, record the error code if there was one, and the line it names.

One of these will not build. The other builds, runs, and gives a different answer than the version with parentheses. Say which is which, and what the second one printed instead.

Challenge (Optional): Say the Same Thing Backwards

• allFine and anyLow look like opposites. Add a line that stores !anyLow and print it next to allFine.
• Try several sets of readings, including ones where two systems are low. Do the two values ever disagree?
• Write a comment saying whether !anyLow and allFine mean the same thing, and how you convinced yourself.

Same Idea, Exam Notation

bool canLaunch = fuelOk && crewOk;
bool anyFault = fuelLow || powerLow;
bool allClear = !anyFault;

canLaunch ← fuelOk AND crewOk
anyFault ← fuelLow OR powerLow
allClear ← NOT anyFault

This is one of the easy panels. The exam writes the operators as words, and the words are exactly what the symbols mean.

Reading them aloud is a genuine exam technique. NOT anyFault says what it does. !anyFault says the same thing, and the exclamation mark is easy to miss in a long line — which is exactly how it gets misread under time pressure.

Checkpoint

Your finished program should run like this.

Any system low: True
All systems fine: False
Not all fine: True

STATUS: attention required
Cleared for long haul.

Crew size? 1 [Enter]
Cargo mass? 300 [Enter]
LAUNCH DENIED

• Every boolean prints True or False, with a capital letter
• You have the three printed values from Task 1 with all readings above 25
• You found readings that give nominal and short trips only together, and wrote them down
• All four Task 3 combinations were tested, and exactly one approves
• Both Task 4 results are recorded — which one refused to build, and what the other one printed instead

Reflection

Answer the following questions before submitting your work.

1. day == 6 || 7 reads like correct English but will not compile. Explain what || actually needs on each side.
2. Task 4's second change built and ran without a single warning, and gave a different answer. Whose job is it to catch that kind of mistake, and what is the cheapest way to avoid it?
3. You could write anyLow as one combined condition, or as three separate if statements. What does storing it in a named boolean give you that neither of those does?

Submit

Submit four things to the dropbox:

1. Your 1-15-systems program file.
2. Your Task 1 all-above-25 values, and the readings that gave nominal and short trips only together.
3. Your four Task 3 combinations, and both Task 4 results with error codes and line numbers.
4. Your three reflection answers.

Activity Complete