Data Representation

Exam objectives

• Convert between decimal, binary, octal and hexadecimal in both directions
• Represent signed integers using signed-magnitude, one's complement and two's complement
• Explain the role of the MSB as a sign bit and why two's complement is preferred for arithmetic

Important areas to cover

• Number-system conversion and complement questions are near-guaranteed every year — in MCQ as quick conversions and in Paper II Part A as multi-step problems
• Two's complement is the single most consistently examined numeric skill in this unit — drill it until automatic

Exam objectives

• List character-encoding schemes: BCD, EBCDIC, ASCII, Unicode
• Convert a given symbol or string into a stated encoding scheme
• State an advantage/disadvantage of each scheme (e.g. ASCII's limited range vs Unicode's multilingual support)

Important areas to cover

• "Why is Unicode needed for Sinhala/Tamil text" is a common local-context question

Exam objectives

• Add and subtract multi-digit binary integers, with carry/borrow shown
• Perform bitwise NOT, AND, OR and XOR operations on binary numbers

Important areas to cover

• Binary addition/subtraction with full working shown is a reliable Paper II Part A question
• Bitwise-operation MCQs (evaluate the result) are common