CAIE IGCSE Computer Science (0478) Theory Study Notes

1.1. Number Systems (Updated)

• Binary System: Base $2$ number system.

  • It has two possible values only ($0$ and $1$).

  • $0$ represents OFF (False), and $1$ represents ON (True).

  • MSB (Most Significant Bit): The left-most bit in a binary number.

  • LSB (Least Significant Bit): The right-most bit in a binary number.

• Denary System: Base $10$ number system.

  • Has values from $0$ to $9$.

• Hexadecimal (Hex): Base $16$ number system.

  • Values from $0$ to $9$ followed by characters $A$ to $F$.

  • Mapping: $A = 10$, $B = 11$, $C = 12$, $D = 13$, $E = 14$, $F = 15$.

1.5. Text, Sound, and Images (Updated)

• Audio Encoding:

  • Sound is converted from analogue to digital via sampling at regular intervals.

  • Sampling Resolution (Bit Depth): Number of bits per sample. High resolution increases accuracy and file size.

  • Sampling Rate: Samples taken per second, measured in Hertz ($Hz$).

• Images:

  • Bitmap/Raster: Made of pixels, stored as binary.

  • Colour Depth: Bits per pixel. $n$ bits allows for $2^{n}$ colors. True colour uses $24$ bits ($8$ bits each for Red, Green, Blue).

  • Resolution: Pixels making up the image (e.g., $4096 \times 3072$). Low resolution leads to pixelated (blurry) images.

1.8. Data Storage and Compression

• Types of Storage:

  • Hard drives, SSDs, optical disks, and cloud storage solutions.

• Compression Techniques:

  • Lossy Compression: Reduces file size by losing some data (e.g., JPEG, MP3).

  • Lossless Compression: Retains original data without loss.

1.9. Types and Methods of Data Transmission

• Transmission Modes:

  • Simplex, half-duplex, and full-duplex.

• Data Transmission Methods:

  • Wired (copper, fiber-optic) and wireless (Wi-Fi, Bluetooth).

1.10. Methods of Error Detection

• Parity Bits: Single bit added for error detection.

• Checksums: Calculated value for data integrity.

• Cyclic Redundancy Check (CRC): Advanced error detection method.

1.11. Input and Output Devices

• Input Devices: Keyboards, mice, scanners, and cameras.

• Output Devices: Monitors, printers, and speakers.

1.12. Sensors

• Devices that detect and respond to physical stimuli (e.g., temperature, motion).

1.13. Data Encryption

• Techniques to secure data from unauthorized access (e.g., AES, RSA, hashing).

1.14. Internet and WWW

• Internet: A global network connecting millions of private, public, academic, business, and government networks.

• World Wide Web (WWW): An information system enabling access to documents and resources via the internet.

1.15. Types of Software

• System Software: Operating systems and utility software for hardware management.

• Application Software: Programs designed for end-users (e.g., word processors, web browsers).