This guide explains how computers handle data using number systems. Mastering conversions is key.

1. Short Notes: Core Concepts

a) Why Binary?

• Computers use electronic circuits that are either ON (1) or OFF (0).

• The binary number system uses only two digits, 1 and 0, to represent these two states. This is why all data inside a computer is stored in binary.

b) Number Systems

• Decimal (Base 10): The system we use daily (digits 0-9).

• Binary (Base 2): The system computers use (digits 0, 1).

• Octal (Base 8): Uses digits 0-7.

• Hexadecimal (Base 16): Uses digits 0-9 and letters A-F.

c) Number System Conversions

• Decimal to Other Bases:

  • Continuously divide the decimal number by the new base (e.g., 2 for binary).

  • The answer is the remainders read from bottom to top.

• Other Bases to Decimal:

  • Multiply each digit by its positional value (the base raised to a power).

  • Add up all the results.

• Binary <-> Octal: Group binary digits into sets of 3.

• Binary <-> Hexadecimal: Group binary digits into sets of 4.

d) Units of Data Storage

• Bit: The smallest unit of data, a 0 or 1.

• Byte: A group of 8 bits.

• Hierarchy: Bit -> Byte -> Kilobyte (KB) -> Megabyte (MB) -> Gigabyte (GB) -> Terabyte (TB).

• Each unit is 1024 times larger than the previous one (1 KB = 1024 Bytes).

e) Coding Systems

• ASCII: An older system using 7 or 8 bits. Good for English.

• Unicode: A modern system using 16 bits. Essential for representing all world languages, including Sinhala and Tamil.

2. Tips and Tricks for the Exam

• Grouping Trick: For Octal, think "Oc-tal" has 3 syllables -> group by 3 bits. For Hexadecimal -> group by 4 bits (since 2⁴ = 16).

• Practice Tip: Do at least 5-10 conversion problems of each type before the exam. This is a section where you can get guaranteed marks.

• Storage Units Trick: Remember that in computing, "Kilo" means 1024, not 1000.

3. Important Points to Remember

• All data in a computer is represented in Binary.

• Unicode is the standard used today because it supports all languages.

• A Byte is made of 8 Bits.