Exploring Computer Science – Comprehensive Midterm Notes

Planning / Problem-Solving Process

• Ordered Steps (know exact sequence)
  • Define / Understand the Problem – clarify goals, constraints, stakeholders.
  • Research & Generate Ideas – gather information, data, prior solutions.
  • Brainstorm / Make a Plan – sketch multiple approaches; select tools, timeline.
  • Explore Possibilities – prototype, simulate, weigh pros & cons.
  • Select an Approach / Carry Out the Plan – implement chosen solution.
  • Reflection / Review – test, evaluate results, document lessons learned.

Computer Fundamentals

Core Definitions

• Computer – “one that computes; a programmable electronic device that can store, retrieve, and process data.”
• Computing – “to determine or calculate, especially by mathematical means or by using a computer.”

Major Hardware / Software Components

• Central Processing Unit (CPU)
  • Executes basic operations, exchanges data with memory & peripherals, orchestrates everything else.
• Operating System (OS)
  • The master program that manages hardware, files, user interface, and provides a platform for other programs.
• Memory (RAM)
  • Temporarily stores data / instructions for quick CPU access; volatile.
• Hard Drive (Mass Storage)
  • Long-term, non-volatile storage using magnetic platters (HDD) or flash (SSD).
  • SSD vs. HDD
  • SSD – Pro: speed, small size; Con: cost.
  • HDD – Pro: low cost, availability; Con: slower, larger physical size.
• Optical Disk Drive – Uses laser/electromagnetic waves to read/write CDs, DVDs, Blu-ray.
• Monitor – Video display screen.
• Video Card (GPU) – Generates the visual output sent to a monitor.
• Sound Card – Generates or reproduces audio; interfaces with speakers.
• Keyboard – Primary text input device.
• Mouse – Hand-held pointing device that controls on-screen pointer.
• Modem – Converts digital computer signals to analog telephone (or other medium) and back.

World Wide Web & Search Engines

• Web 1.0 vs. Web 2.0
  • Web 1.0 – static pages, read-only, minimal user interaction.
  • Web 2.0 – dynamic, user-generated content, social networking, collaboration.
• Search Engine – Program that indexes the web and returns ranked pages matching a query.
  • Main players: Google, Bing, Yahoo, DuckDuckGo, Baidu, Yandex.
• Search Syntax (symbols / keywords)
  • Combine keywords → AND or implicit space.
  • Exclude words / sites → -keyword or site:-example.com.
  • Weather for location → weather city (e.g., weather Boston).
  • Dictionary definition → define:word.
• Website Evaluation Criteria
  • Accuracy – correctness, verifiable sources.
  • Authority – author’s credentials, domain reputation.
  • Objectivity – bias, purpose (inform/persuade/sell).
  • Accessibility – ease of use, navigation, ADA compliance, load speed.

Computer Programs

• Program – a set of instructions that tell a computer what to do.

Artificial Intelligence (AI)

• Turing Test – Proposed by Alan Turing; if a human interrogator cannot distinguish the machine’s responses from a human’s, the machine is said to exhibit intelligence.
• Artificial Intelligence – The field concerned with making computers perform tasks that normally require human intelligence.
• Key AI Capabilities
  • Acoustic Processing – handling sound waves, filtering noise.
  • Speech Recognition – converting spoken words to text.
  • Facial Recognition – identifying or verifying persons from images.

Binary Number System

• Concept – base-2 system using digits $0$ and $1$.

Decimal → Binary (LEFT → RIGHT)

• Show card = 1, hide card = 0.
• Example: $31_{10}$
  • $16 + 8 + 4 + 2 + 1 = 31$ → binary: $11111$.

Binary → Decimal (LEFT → RIGHT)

• Example: $11111_2$ → $16 + 8 + 4 + 2 + 1 = 31$.

Capacity Rule

• “Add 1 bit, double patterns.” Mathematically: $2^n$ patterns for $n$ bits.
  • 1 bit → 2
  • 2 bits → 4
  • …
  • 8 bits → 256 (one byte)

Decoding Messages

• Convert binary to decimal, map to alphabet table (1 = a, 2 = b, … 26 = z).

Graph Theory: Spanning Trees

• Spanning Tree – A sub-graph that connects all vertices with the minimum possible edges (no cycles).
• The sample graph shown has 16 possible spanning trees.
• Minimum Spanning Tree (MST) – Spanning tree whose total edge weight is minimum; useful in networking, circuit design, clustering, route planning.

Programming Concepts (Code.org)

Debugging

• Process of locating & fixing errors (bugs) that prevent correct software operation.

Coordinate System (Game Lab)

• Uses $X$ (horizontal) & $Y$ (vertical) coordinates.
• Screen origin: top-left $(0,0)$.

Variables

• Container for data.
• Naming Rules
  • No spaces.
  • Cannot start with number.
  • Case-sensitive; spelling must be exact.
• Style
  • camelCase: sizeOfRectangle.
  • underscores: size_of_rectangle.
  • Choose meaningful names; maintain consistency.

Boolean Logic & Conditionals

• Boolean value – $\text{true}$ / $\text{false}$.
• Comparison Operators
  • Less-than $<$, greater-than $>$, equal $==$.
• Conditional Statements
  • if (condition) {…}
  • if … else … – choose between two code blocks.

Draw Loop & Animation

• Program flow in Game Lab
  1. Run all code outside draw() once.
  2. Execute code inside draw() repeatedly (~30 frames per second).
• Definitions
  • Animation – series of images (frames) creating motion.
  • Frame – single image.
  • Frame Rate – frames per second.
• Randomness
  • Pseudo-random – algorithmic.
  • True random – physical process.
• Velocity Blocks
  • velocityX, velocityY change position automatically each frame.
  • Equivalent to counter pattern: sprite.x = sprite.x + 1;.

Functions

• Group of commands given a name; enables reuse.
• Creating – wrap commands in a function block, give it a name.
• Calling – write functionName(); wherever needed.
• Advantages
  1. Organizes code (large blocks can sit out of the way).
  2. Improves readability (names explain purpose).
  3. Removes repetition (change code in one place).