Data Representation and Data Types

What Data Representation and Data Types covers

Data Representation and Data Types is examined in AS Unit 1, Fundamentals of Computer Science. It covers bits, bytes and words, the binary number system, hexadecimal notation, character sets and storing characters, primitive data types and storage requirements, binary arithmetic and negative numbers and real numbers, truncation and rounding.

The 7 subtopics

Each one has its own page. WJEC AS Computer Science students sit this topic in the first year.

• Bits, bytes and wordsWord length of a processor and kilobyte and a kibibyte.Open →
• The binary number systemColumn values in an eight-bit binary number, largest value eight bits can hold as an unsigned number and largest unsigned value that fits in sixteen bits.Open →
• Hexadecimal notationRecall questions on the base and its digits, why it is used as shorthand for binary, converting between binary, hexadecimal and denary, how many values two and three digits hold, where hexadecimal is used in practice, and why nibbles are grouped from the right.Open →
• Character sets and storing charactersCharacter set and extended ASCII.Open →
• Primitive data types and storage requirementsPrimitive data type, range of a sixteen-bit signed integer and range of an eight-bit unsigned integer.Open →
• Binary arithmetic and negative numbersRules for adding two binary digits, overflow in fixed-length binary addition and range of values an eight-bit two's complement store can hold.Open →
• Real numbers, truncation and roundingColumn values to the right of a binary point and limitation of a fixed point format.Open →

What you need to know

Answer each one before you reveal it.

Take Data Representation and Data Types further

The same content, four other ways.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is a bit?

   Model answer

   A bit is the smallest unit of data a computer holds, a single binary digit that is either 0 or 1.

2. 2

   Why do computers work in binary rather than in denary?

   Model answer

   An electronic circuit can distinguish two states such as on and off reliably even when voltages drift, whereas telling ten separate voltage levels apart would be slow and error-prone.

3. 3

   What is a byte?

   Model answer

   A byte is a group of eight bits, and it is the smallest block that is normally given its own address in memory.

4. 4

   What is a nibble, and why is it a convenient grouping?

   Model answer

   A nibble is four bits, half a byte, and it is convenient because one nibble corresponds to exactly one hexadecimal digit.

5. 5

   What is meant by the word length of a processor?

   Model answer

   The word length is the number of bits the processor handles as a single unit, which is the width of its registers and of the data it moves and operates on in one go.

6. 6

   What word lengths are usual in general purpose processors today?

   Model answer

   Thirty-two bits and sixty-four bits are the usual sizes, with sixty-four bits now standard in desktop and mobile machines.

What is inside Levo

Six ways to work the same material.

Data Representation and Data Types revision questions

Is Data Representation and Data Types examined at AS in WJEC Computer Science?

Yes. It sits in AS Unit 1, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.

What does Data Representation and Data Types cover in WJEC AS-Level Computer Science?

7 subtopics: bits, bytes and words, the binary number system, hexadecimal notation, character sets and storing characters, primitive data types and storage requirements, binary arithmetic and negative numbers and real numbers, truncation and rounding. Each one has its own page with questions and model answers.

How is Data Representation and Data Types organised?

By the WJEC 601-5345-3 specification, subtopic by subtopic, so it matches the order you are taught it in.