TECHNOLOGY 

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KembaraXtra – Computer Terms – @ means:
This symbol is central to email communication. It separates the username from the domain name in an email address. For example, in user@example.com, the @ reads as “at” and indicates that the user is associated with the example.com domain. It’s also used in other Internet services and authentication formats.


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KembaraXtra – Computer Terms – \ means:
The backslash is a directory path separator used in Windows and MS-DOS systems. Unlike UNIX, which uses forward slashes, Windows uses backslashes in file paths—for example, C:\Program Files\. When placed at the beginning of a path, it means that the path begins from the root of the disk.


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KembaraXtra – Computer Terms – 0.07-micron means:
This refers to a semiconductor manufacturing process where features on a chip are only 0.07 microns wide—extremely small compared to the width of a human hair. This allows manufacturers to fit around 400 million transistors on a single chip. It leads to high-speed, high-performance processors that can exceed 10 GHz in speed. Applications include powerful computers, ultra-fast hard drives, and even medical devices like implanted hearing aids.


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KembaraXtra - Computer Science - Prefixes in Computing

1. Introduction to Prefixes

  • Purpose: Prefixes are used to represent large quantities of data (bits and bytes) in a concise and understandable way.
  • SI Prefixes (Metric System): A standardized system of prefixes used to quantify various measurements, including data sizes.

2. Common SI Prefixes (Base 10)

Prefix Name Prefix Symbol Value Base 10 English Word
tera T 1,000,000,000,000 10¹² trillion
giga G 1,000,000,000 10⁹ billion
mega M 1,000,000 10⁶ million
kilo k 1,000 10³ thousand
centi c 0.01 10⁻² hundredth
milli m 0.001 10⁻³ thousandth
micro μ 0.000001 10⁻⁶ millionth
nano n 0.000000001 10⁻⁹ billionth
pico p 0.000000000001 10⁻¹² trillionth
  • Usage: 3 billion bytes = 3GB; 4 thousand bits = 4kb
  • Case Sensitivity: 'B' = Byte, 'b' = bit

3. Base 2 vs. Base 10 in Computing

  • Bytes and Base 2: Computers internally operate in base 2 (binary).
  • "1MB" Misconception: A file labeled as "1MB" is often 1,048,576 bytes (2²⁰), not exactly 1,000,000 bytes.

4. SI Prefix Meaning When Applied to Bytes (Base 2)

Prefix Name Prefix Symbol Value Base 2
tera T 1,099,511,627,776 2⁴⁰
giga G 1,073,741,824 2³⁰
mega M 1,048,576 2²⁰
kilo k 1,024 2¹⁰

5. Network Transfer Rates

  • Advertisements: Internet speed is advertised in bits per second (base 10).
  • Conversion: To find the equivalent in bytes per second, divide the advertised speed by 8 (bits per byte).
  • Example: 50 Mbps internet = 50,000,000 bits/second = 6,250,000 bytes/second ≈ 6 MB/second.

6. IEEE 1541-2002 Prefixes for Binary Data

  • Purpose: Introduced to remove ambiguity between base 10 and base 2 interpretations of SI prefixes.
  • New Prefixes: kibi (Ki), mebi (Mi), gibi (Gi), tebi (Ti) are used to explicitly indicate powers of 2.
  • Intended Usage:
    • "kilobyte" (kB) should mean 1,000 bytes (base 10).
    • "kibibyte" (KiB) should mean 1,024 bytes (base 2).

7. IEEE 1541-2002 Prefixes Table

Prefix Name Prefix Symbol Value Base 2
tebi Ti 1,099,511,627,776 2⁴⁰
gibi Gi 1,073,741,824 2³⁰
mebi Mi 1,048,576 2²⁰
kibi Ki 1,024 2¹⁰

8. Practical Implications and Common Misunderstandings

  • Software Display: Most software uses the old SI prefixes (KB, MB, GB) but calculates sizes in base 2.
  • Storage Device Marketing: Manufacturers advertise storage capacity using base 10.
  • A "1TB" hard drive (1,000,000,000,000 bytes) will appear as roughly "931GB" when connected to a computer (1,000,000,000,000 bytes / 2³⁰).
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KembaraXtra – Computer Terms – / means:
The forward slash is used in UNIX and web-based systems to separate parts of a file path or a web address. For example, /home/user/documents is a typical path in UNIX. It’s also used in FTP paths and URLs. In command-line operations, it acts as a prefix to options or parameters that modify how a command runs, such as /p for pause or /s for recursive directory operations.


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KembaraXtra-Computer Science-Ohm's Law
1. Ohm's Law Explained
  • Definition: Defines the relationship between current (I), voltage (V), and resistance (R) in a circuit.
  • Formula: I = V / R
    • I: Current (measured in Amperes or Amps)
    • V: Voltage (measured in Volts)
    • R: Resistance (measured in Ohms Ω)
  • Concept: The current flowing between two points is directly proportional to the voltage across those points and inversely proportional to the resistance between them.
2. Applying Ohm's Law
  • Example: A 9V battery connected to a 10,000Ω resistor.
    • I = 9V / 10,000Ω = 0.0009 Amps = 0.9 mA (milliamps)
  • Key Takeaway: You can calculate any one of the three values (I, V, or R) if you know the other two.
3. AC vs. DC
  • AC (Alternating Current):
    • Electric current that periodically reverses direction.
    • Used for transmitting electricity over long distances (power grids).
    • Powers appliances plugged directly into wall sockets (without an adapter).
  • DC (Direct Current):
    • Electric current that flows in one direction only.
    • Provided by batteries.
    • Used by most smaller electronics (laptops, smartphones).
    • Often requires AC to DC conversion using an adapter.
  • AC/DC Voltage: The terms apply to voltage sources, meaning "alternating voltage" or "direct voltage" respectively.
  • Focus: This text primarily focuses on DC circuits.



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KembaraXtra-Computer Science - Electrical Terms

I. Key Concepts Overview

Term Explanation Measured in Water Analogy
Electric Charge Causes matter to experience a force Coulombs Water
Electric Current The flow of charge Amps Flow of water through pipe
Voltage Potential difference between two points Volts Water pressure
Resistance Difficulty for current to flow Ohms Width of a pipe

II. Electric Charge

  • Definition: A fundamental property of matter that causes it to experience a force when placed in an electromagnetic field.
  • Types: Positive (protons) and negative (electrons).
  • Interaction: Like charges repel, unlike charges attract.
  • Unit: Coulomb (C)
  • Water Analogy: Water itself

III. Electric Current

  • Definition: The flow of electric charge. (Technically, charge flows, and current is the measurement of that flow.)
  • Symbol: I or i
  • Unit: Ampere (A), often called "amps"
  • 1 Ampere = 1 Coulomb per second (1A = 1 C/s)
  • Interpretation: Amps represent the rate at which charge is moving.
  • Water Analogy: The rate of water flowing through a pipe

IV. Voltage

  • Definition: The difference in electric potential between two points. It represents the work required to move a unit of charge from one point to another.
  • Electric Potential: Potential energy per unit charge (Joules per Coulomb).
  • Symbol: V or v
  • Unit: Volt (V)
  • Measurement: Always measured between two points (e.g., terminals of a battery).
  • Relationship to Current: Voltage influences current. Higher voltage = greater "pressure" to move charge, resulting in higher current (given the same resistance).
  • Important Note: Voltage can exist without current flow (e.g., a battery not connected to a circuit).
  • Water Analogy: Water pressure

V. Resistance

  • Definition: A measure of how difficult it is for current to flow through a material.
  • Conductor: A material that allows current to flow easily (e.g., copper wire - assumed to have near-zero resistance).
  • Resistor: An electrical component designed to introduce a specific amount of resistance into a circuit.
  • Symbol: R
  • Unit: Ohm (Ω - Greek letter omega)
  • Impact on Current: Higher resistance = lower current (given the same voltage).
  • Water Analogy: The width of a pipe. A narrow pipe offers high resistance to water flow.

VI. The Water Analogy Revisited

  • Pump: Battery (provides voltage/pressure)
  • Water: Electric charge
  • Flow of Water: Electric current
  • Water Pressure: Voltage
  • Wide Pipe: Conductor (low resistance)
  • Narrow Pipe: Resistor (high resistance)

VII. Example Circuit

  • Components: Battery (voltage source) and a conductor.
  • Process:
    • i. Potential Energy: Stored in the battery.
    • ii. Voltage: Exists across the battery terminals.
    • iii. Connection: When the conductor is connected, the voltage "pushes" charge through the conductor, creating current.
    • iv. Resistance: The conductor's resistance affects the current. Low resistance = large current, High resistance = small current.

VII. Example Circuit

  • Components: Battery (voltage source) and a conductor.
  • Process:
    • i. Potential Energy: Stored in the battery.
    • ii. Voltage: Exists across the battery terminals.
    • iii. Connection: When the conductor is connected, the voltage "pushes" charge through the conductor, creating current.
    • iv. Resistance: The conductor's resistance affects the current. Low resistance = large current, High resistance = small current.
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KembaraXtra-Computer Science - Binary Logic

Core Concept

  • Computers use binary logic to process data. This system uses true (1) or false (0) values to represent logical statements.

Why Binary for Logic?

  • Logic deals with true/false statements.
  • A bit has two states: 1 or 0.
  • Therefore, a bit can represent a true/false logical state.

Truth Tables

  • Definition: A table showing all possible combinations of input conditions and their logical outcomes.
  • Used to express how components behave given certain inputs.

Example: Rectangle Logic

Statement: If a shape has four sides AND four right angles, then it's a rectangle.

Four Sides Four Right Angles Rectangle
False False False
False True False
True False False
True True True

Generic AND Truth Table

A B Output
False False False
False True False
True False False
True True True

AND Truth Table (Binary)

A B Output
0 0 0
0 1 0
1 0 0
1 1 1

OR Truth Table (Binary)

A B Output
0 0 0
0 1 1
1 0 1
1 1 1

Combining AND and OR

Example: (A AND B) OR C

A B C Output
0 0 0 0
0 0 1 1
0 1 0 0
0 1 1 1
1 0 0 0
1 0 1 1
1 1 0 1
1 1 1 1

Other Logical Operators

NOT

  • Reverses the input.
A Output
0 1
1 0

NAND (NOT AND)

  • Reverse of AND. Output is false only when both inputs are true.
A B Output
0 0 1
0 1 1
1 0 1
1 1 0

NOR (NOT OR)

  • Reverse of OR. Output is true only when both inputs are false.
A B Output
0 0 1
0 1 0
1 0 0
1 1 0

XOR (Exclusive OR)

  • Output is true only if one of the inputs is true, but not both.
A B Output
0 0 0
0 1 1
1 0 1
1 1 0

Boolean Algebra

  • Study of logical functions with true/false variables.
  • Developed by George Boole.
  • Fundamental to digital electronics and computers.
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KembaraXtra-Computer Science-Representing Data Digitally
1. Digital Representation of Data
  • Computers store all data as bits (0s and 1s).
  • This includes:
    • Negative numbers
    • Fractional numbers
    • Text
    • Colors
    • Images
    • Audio
    • Video
2. Digital Text
  • Text is represented as a collection of alphanumeric and related symbols (characters).
  • Includes:
    • A-Z (uppercase and lowercase - distinct)
    • Punctuation marks (e.g., commas, periods)
    • Spaces
    • Digits 0-9 (as symbols, not numerical values)
  • String: a sequence of text characters (common term in programming).
  • Encoding: Translating data into a digital format.
  • Decoding: Interpreting digital data.
2.1 Representing Text with Bits
  • Around 100 characters need to be represented.
  • 6 bits: 64 unique combinations (not enough)
  • 7 bits: 128 unique combinations (enough)
  • Commonly, 8 bits (1 byte) are used to represent each character (256 unique characters possible).
  • Any scheme can be used to represent characters as bits, as long as the software knows the scheme.
  • Software designers prefer schemes that make operations easy.
2.2 ASCII
  • American Standard Code for Information Interchange.
  • Standard for representing text digitally.
  • Represents 128 characters using 7 bits (often stored as 8 bits, with a leading 0).
  • Handles English characters.
2.3 Unicode
  • Another standard that handles characters in nearly all languages, including English.
3. Digital Colors and Images
3.1 Grayscale Representation
  • Limiting colors to black, white, and shades of gray.
  • Example: Representing black, white, dark gray, and light gray (4 colors) requires 2 bits (2^2 = 4).
3.2 Representing Images
  • An image is an arrangement of colors on a two-dimensional plane.
  • Colors are arranged in a grid of single-color squares called pixels.
  • An image's dimensions are defined by its width and height in pixels.
3.3 Standard Approaches for Colors and Images
  • Grayscale: 8 bits per pixel allows for 256 shades of gray (0 = black, 255 = white).
  • RGB: Uses three 8-bit numbers to represent the intensity of Red, Green, and Blue. This means 24 bits represent the overall color.
    • Additive color model: colors composed of a mix of red, green, and blue light.
    • Each component color can vary from 0 (darker shade) to 255 (brighter shade).
3.4 Image Formats
  • Bitmap: Stores RGB color data for each individual pixel (simplistic).
  • JPEG and PNG: Use compression techniques to reduce the number of bytes to store an image.
4. Interpreting Binary Data
  • A single binary value can have different meanings depending on the context.
    • Example: 011000010110001001100011
      • ASCII text string: "abc"
      • 24-bit RGB color: a shade of gray
      • Positive integer: 6,382,179 (decimal)
  • The interpretation depends on the software used to process the data (text editor, image viewer, calculator, etc.).
  • Programs are written to expect data in a particular format.
5. General Principles
  • Any type of data can be represented digitally (numbers, text, colors, images, audio, video, etc.).
  • The digital representation may not be a perfect replica, but is often sufficient.
  • Representing data as 0s and 1s is useful because a device that works with binary data can be adapted to deal with any kind of data through software.
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KembaraXtra - Computer Science - Hexadecimal

Introduction

  • Hexadecimal (or hex) is a base-16 number system.
  • It's used to represent binary numbers in a more human-readable format.

Understanding Hexadecimal

  • Place Value: Each position represents a power of 16 (ones, sixteens, 256s, 4096s, etc.).
  • Symbols: Uses 16 symbols: 0-9 and A-F.
  • A = 10, B = 11, C = 12, D = 13, E = 14, F = 15
  • Prefix: 0x is commonly used to indicate a hexadecimal number (e.g., 0x1A).
  • Counting: After 0xF comes 0x10 (decimal 16), then 0x11, 0x12, etc.

Table 1-5: Hexadecimal Symbols

Hexadecimal Decimal Binary (4-bit)
0 0 0000
1 1 0001
2 2 0010
3 3 0011
4 4 0100
5 5 0101
6 6 0110
7 7 0111
8 8 1000
9 9 1001
A 10 1010
B 11 1011
C 12 1100
D 13 1101
E 14 1110
F 15 1111

Converting Hexadecimal to Decimal

Multiply the decimal equivalent of each hex digit by its corresponding power of 16.

Example: 0x1A5

  • 5 is in the ones place: 5 * 1 = 5
  • A (10) is in the sixteens place: 10 * 16 = 160
  • 1 is in the 256s place: 1 * 256 = 256
  • Total: 5 + 160 + 256 = 421

Why Use Hexadecimal?

  • Readability: Easier to read and write than long binary sequences.
  • Conversion to Binary: Straightforward conversion between hexadecimal and binary.

Relationship Between Hexadecimal and Binary

  • Each hexadecimal symbol represents 4 bits (a nibble).
  • A byte (8 bits) can be represented by two hexadecimal symbols.
  • A 16-bit number can be represented by four hex symbols.
  • A 32-bit number can be represented by eight hex symbols.

Converting Binary to Hexadecimal

  1. Group the binary number into groups of 4 bits, starting from the right.
  2. Convert each group of 4 bits into its corresponding hexadecimal symbol.

Converting Hexadecimal to Binary

  1. Convert each hexadecimal digit to its 4-bit binary equivalent.
  2. Concatenate the binary equivalents.

Exercises

EXERCISE 1-4: BINARY TO HEXADECIMAL

Convert these numbers, represented in binary, to their hexadecimal equivalents. Don’t convert to decimal if you can help it! The goal is to move directly from binary to hexadecimal.

10 (binary) = ______ (hexadecimal)

11110000 (binary) = ______ (hexadecimal)

EXERCISE 1-5: HEXADECIMAL TO BINARY

Convert these numbers, represented in hexadecimal, to their binary equivalents. Don’t convert to decimal if you can help it! The goal is to move directly from hexadecimal to binary.

1A (hexadecimal) = _____ (binary)

C3A0 (hexadecimal) = ______ (binary)

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