Data Representation
13.1 User-defined data types
Candidates should be able to:
- Show understanding of why user-defined types are necessary
- Define and use non-composite types
Notes and guidance
Including enumerated, pointer
- Define and use composite data types
Notes and guidance
Including set, record and class/object
- Choose and design an appropriate user-defined data type for a given problem
13.2 File organisation and access
Candidates should be able to:
- Show understanding of the methods of file organisation and select an appropriate method of file organisation and file access for a given problem
Notes and guidance
Including serial, sequential (using a key field), random (using a record key)
- Show understanding of methods of file access
Notes and guidance
Including Sequential access for serial and sequential files Direct access for sequential and random files
- Show understanding of hashing algorithms
Notes and guidance
Describe and use different hashing algorithms to read from and write data to a random / sequential file
13.3 Floating-point numbers, representation and manipulation
Candidates should be able to:
- Describe the format of binary floating-point real numbers
Notes and guidance
- Use two’s complement form
- Understand of the effects of changing the allocation of bits to mantissa and exponent in a floating-point representation
- Convert binary floating-point real numbers into denary and vice versa
- Normalise floating-point numbers
Notes and guidance
Understand the reasons for normalisation
- Show understanding of the consequences of a binary representation only being an approximation to the real number it represents (in certain cases)
Notes and guidance
Understand how underflow and overflow can occur
- Show understanding that binary representations can give rise to rounding errors