A-level Computing 2009/AQA/Problem Solving, Programming, Data Representation and Practical Exercise/Fundamentals of Data Representation

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From the Specification : Binary number system

Pure Binary Representation of Denary Integer

  • Describe the representation of unsigned denary integers in binary. Perform conversion from denary to binary and vice-versa.

Binary Arithmetic

  • Add two binary numbers and multiply two binary numbers.

Representation of signed integers by Two’s Complement

  • Describe the use of Two’s Complement to perform subtraction. Convert a denary integer into Two’s Complement and vice versa.

The Concept of Number Bases: Denary, Binary and Hexadecimal

  • Describe the conversion of a denary integer to hexadecimal form and vice versa. Describe the use of hexadecimal as shorthand for binary.

Integers and Numbers with a Fractional Part

  • Draw a distinction between integers and numbers with a fractional part in a computer context.Describe how an unsigned denary number with a fractional part is represented in fixed-point form in binary.
From the Specification : Information Coding Schemes

Describe standard coding systems for coding character data.

  • Understand ASCII
  • Understand Unicode

Differentiate between the character code representation of a denary digit and its pure binary representation. Error checking and correction

  • Parity bits, Hamming code.

Gray coding

  • Describe Gray coding. Explain why and where it is used.
From the Specification : Representing Images, Sound and other data


Describe how bit patterns may represent other forms of data including graphics and sound.
Bitmapped Graphics
  • Bitmaps: resolution, colour depth and simple bitmap file calculations.
Vector Graphics
  • Vector graphics: drawing list – objects and their properties.
Compare bitmaps to vector graphics; advantages, disadvantages.
The need for compression and basic techniques for compression.

Sound files

The need for compression and basic techniques for compression.
Sampled Sound and Nyquist-theorem
  • Sampling resolution, sampling rate.
Sound Synthesis
  • Describe MIDI and its advantages for storing sound digitally.
Streaming audio
  • Explain what it is and why it is used.
Analogue and Digital Data. Analogue and Digital Signals
  • Differentiate between analogue and digital data and analogue and digital signals.
Analogue to Digital Converter
  • (ADC) Describe the principles of operation of an analogue to digital converter.