AP Computer Science Principles: The Night Before 🚀

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Big Idea 3: Algorithms and Programming

What's an Algorithm?

An algorithm is simply a set of instructions to solve a problem or complete a task. Think of it as the logic behind a process. It's like the steps you'd take to make a cake, while the program is the recipe itself. 🍰

Building Blocks: Sequencing, Selection, and Iteration

Every algorithm is built using three core concepts:

• Sequencing: Steps are executed in the order they appear. It's like following a recipe from top to bottom.

  first_number = 7
  second_number = 5
  sum_value = first_number + second_number
  print (sum_value)
  

  In this example, each line is executed one after the other.

• Selection: (We'll cover this later) This is where your code makes decisions (like if/else statements).

• Iteration: (We'll cover this later) This is how you repeat steps (loops like for and while).

Expressions: Getting to a Single Value

An expression is anything that returns a single value. It can be a number, a variable, or a calculation using operators.

Arithmetic Operators

Here are the operators you'll use in your code:

Order of Operations

Expressions are evaluated using the order of operations (PEMDAS, or PEMMDAS if you include MOD). Remember:

1. Parentheses
2. Exponents
3. Multiplication or Division (from left to right)
4. MOD
5. Addition or Subtraction (from left to right)

{
"multiple_choice": [
{
"question": "What is the result of the expression `20 MOD 7`?",
"options": ["2", "3", "6", "20"],
"answer": "6"
},
{
"question": "Which of the following is NOT an example of an algorithm?",
"options": ["A recipe for baking a cake", "A set of instructions to assemble a desk", "A random collection of words", "A sequence of steps to solve a math problem"],
"answer": "A random collection of words"
}
],
"free_response": {
"question": "Write an algorithm in pseudocode to calculate the average of three numbers. The algorithm should:\n1. Take three numbers as input.\n2. Calculate the sum of the three numbers.\n3. Calculate the average by dividing the sum by 3.\n4. Display the average.",
"scoring_breakdown": [
"1 point for taking three numbers as input",
"1 point for calculating the sum of the three numbers",
"1 point for correctly calculating the average",
"1 point for displaying the average"
],
"sample_solution": "```\nINPUT num1\nINPUT num2\nINPUT num3\nsum = num1 + num2 + num3\naverage = sum / 3\nDISPLAY average\n```"
}
}

Final Exam Focus

• Algorithms: Understand what they are and how they're different from programs. Be able to identify algorithms in different forms (code, pseudocode, etc.).
• Sequencing: Know how code executes step-by-step.
• Expressions: Practice evaluating expressions using the correct order of operations, especially with the MOD operator.

Last-Minute Tips

• Time Management: Don't get stuck on one question. Move on and come back if needed.
• Common Pitfalls: Watch out for order of operations errors and be careful with the MOD operator.
• Strategies: Read questions carefully and break them down into smaller parts.

You've got this! Go get 'em! 💪