CAIE AS Level Computer Science Flashcards

1. Information Representation

1.1. Data Representation

• Two fundamental characteristics:

• Base: Number of different digits in the system.
• Place value: Specific value of a digit based on its position.

• Denary (Base 10)
• Binary (Base 2): Uses bits (0 or 1), e.g., 65 in binary = 01000001.

Character Encoding Standards

• ASCII: Represents English alphabet characters, with 128 possible characters (7 bits).
• Extended ASCII: Extends ASCII to include various Latin alphabets.
• Unicode: Superset of ASCII capable of representing many global languages, supports 256 characters (8 bits).

1.2. Multimedia - Graphics, Sound

Bitmap Images

• Definition: Images made by assigning colors to pixels using bit patterns.
• Resolution: Number of pixels; higher resolution = sharper, detailed images.
• Color Depth: Number of bits for color representation; $2^n$ colors for an n-bit image.
• File Size Calculation:

ext{File Size} = ext{Number of Pixels} imes ext{Color Depth}

Sound Representation

• Analog vs. Digital:
  • Analog data: Continuous signals, while Digital data consists of discrete signals.
• Conversion: Analog signals are converted to digital via sampling at regular intervals.
• Sampling rate: Number of samples taken per unit time; impacts accuracy of sound representation.
• Bit Rate: Number of bits to store one second of sound:
  ext{Bit Rate} = ext{Sampling Resolution} imes ext{Sampling Rate}

Vector Graphics

• Definition: Made of objects defined mathematically; can be resized without quality loss.

1.3. Compression

Lossless Compression

• Original data is perfectly reconstructed; e.g., .bmp, .png files.

Lossy Compression

• Data is irreversibly eliminated to reduce size (e.g., .mp3, .jpeg).

2. Communication

2.1. Networks

LAN vs. WAN

• LAN: Local, connects devices within a small area; typically fast with low congestion.
• WAN: Connects devices over larger areas; typically slower with higher congestion.

Networking Types

• Client-server model: Dedicated server handles multiple clients.
• Peer-to-Peer (P2P): Each connected device acts as a client and server.

Network Topologies

1. Bus: Single cable; all devices on the same line.
2. Star: Central node (hub) with dedicated connections.
3. Mesh: Each device connected to all others.

Networking Devices

• Router: Connects different networks, manages traffic.
• Switch: Connects devices in a LAN, directs data packets.

3. Hardware

3.1. Computer Components

• Input: Gathers data from users.
• Output: Displays data for user understanding.
• Storage: Refers to both primary (RAM) and secondary (HDD/SSD) storage.

3.2. Logic Gates

• AND, OR, NOT gates perform basic logical functions in computing.

Processor Fundamentals

4.1. Central Processing Unit (CPU)

• Architecture: Follows Von Neumann model, where data and programs share memory.
• Registers: Fast storage locations in CPU that hold data and instructions.

4.2. Assembly Language

• Low-level programming closely related to machine code.

4.3. Bit Manipulation

• Enables operations like shifting bits to multiply or divide numbers.