#AP Computer Science Principles: The Night Before Cram Session 🚀

Hey there, future AP CS Principles rockstar! Let's make sure you're feeling totally prepped for tomorrow. This guide is designed to be your best friend tonight – quick, clear, and focused on what really matters. Let's do this!

#1. Data Types and Variables

#1.1. Numbers

Integers: Whole numbers (e.g., -3, 0, 42).
Floating-Point Numbers: Numbers with decimal points (e.g., 3.14, -0.5).

Key Concept

Remember, computers store numbers in binary (base-2). This is important for understanding how data is represented and processed.

#1.2. Strings

Definition: Ordered sequences of characters (text).
Indexing: Access individual characters using their position (starting from 0).
- Example: In "Hello", "H" is at index 0, "e" is at index 1, and so on.

#1.2.1. String Slicing

Definition: Extracting a portion (substring) of a string.
Syntax: string[start:end]
- start: Index of the first character to include (inclusive).
- end: Index of the first character not to include (exclusive).

python string_example1 = "APcomputerscienceprinciples" print (string_example1[0:10]) # Output: "APcomputer" print (string_example1[2:9]) # Output: "compute" ```

Exam Tip

Remember that the end index in slicing is exclusive. This is a common source of errors!

#1.2.2. String Concatenation

Definition: Joining two or more strings end-to-end.
Operator: +

python part_one = "Hello" part_two = "_World!" print (part_one + part_two) # Output: "Hello_World!" ```

Memory Aid

Think of concatenation like adding train cars together to make a longer train. Each car (string) is linked to the next.

#1.3. Booleans

Definition: Represents truth values: True or False.
Use: Often used in conditional statements (if/else).

#1.4. Variables

Definition: Named storage locations in memory that hold values.
Assignment: Use the = operator to give a variable a value.
- Example: x = 10

Quick Fact

Variables are like labeled boxes; they store information that can be changed.

#2. Control Structures

#2.1. Sequencing

Definition: Executing code statements in order, one after another.
Default: The normal flow of a program.

#2.2. Selection (if/else)

Definition: Executing different blocks...

Strings

Ben Davis