Level 1 / C# Fundamentals / fundamental 2 of 7
Math, comparisons, and strings
Variables only become useful when you do something with them. An expression is any piece of code that produces a value: 5 + 3, age >= 18, or $"Total: {total}". These reps drill the operators you will reach for every day, building on the declarations from the last drill.
Understand the idea
Arithmetic and its traps
+, -, *, and / do what you expect, and % gives the remainder. Dividing two ints throws away the remainder (7 / 2 is 3), so use a double on at least one side when you want 3.5.
Comparisons produce bools
==, !=, <, >, <=, and >= each give back true or false, which you can store in a bool. && means both must be true, || means at least one, and ! flips true and false.
Shortcuts and interpolation
score += 50 is short for score = score + 50, and total++ adds one. A $ before a string turns on interpolation, so anything in braces is evaluated and dropped into the text.
English to C#
“Make an int called total equal to 5 plus 3.”
int total = 5 + 3;
- int total =
- a declaration, exactly as in the last drill
- 5 + 3
- an expression: evaluated first, then stored
- ;
- ends the statement
Rep 1 of 12
Copy itIn English
Make an int called total equal to 5 plus 3.
Type the code shown below. Watch it turn green as you go.
int total = 5 + 3;
Waiting for you to type · 0 of 7 pieces
Ctrl+Enter checks or moves on. Tab indents. Paste is off on purpose: your hands are learning this too.
Reps
0 of 12 done
Reps unlock in order, because each one builds on the last.
How your code is checked
Drills compare what you type with known-correct C#, token by token. Spacing, line breaks, and comments do not matter; spelling, case, and punctuation do. It is not a compiler, so it accepts the listed spellings of each answer and nothing else.
Try it in a real .NET project
In your console app, read a number with int.Parse(Console.ReadLine()), then print its double, its remainder when divided by 3, and whether it is over 100. Then try 7 / 2 and 7 / 2.0 side by side and explain the difference.
Check your understanding
What does int result = 7 / 2; store, and how would you get 3.5 instead?
Show the explanation
It stores 3. Both operands are ints, so C# does integer division and drops the remainder. Making either side a double, such as 7 / 2.0 or (double)7 / 2, and storing into a double gives 3.5.
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