1.4.1 Data Types Exam Questions
Paper 1 · Computer Systems · 22 past paper questions · 49 marks
Exam questions for 1.4.1 Data types
22 OCR past paper questions (49 marks) with mark schemes
Answer each question, reveal the mark scheme, then award yourself marks. Scores and answers are saved in this browser so you can see which topics need more work.
Download Questions & Mark Scheme (PDF)Past paper questions
- Question 1H446/013 marks
Tick (✓) one box for each piece of data to show if it is an example of a String, Float or Character data type.
Data String Float Character 3.14 'j' 'Hello World' Show mark scheme
3.14 - Float "j" - Character "Hello World" - String (3 marks - 1 per correct match)Mark yourself: how many marks did you get?/ 3 - Question 2H446/012 marks
Beth records how many steps she has completed over a seven-day period. She stores the values in a text file as strings. State the data type the values will need to be converted to and state the reason why.
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Data Type: Integer / real / float / single / double Reason: To complete calculations (on the numeric data) (2 marks - 1 for type, 1 for reason)Mark yourself: how many marks did you get?/ 2 - Question 3H446/012 marks
Explain one benefit of using Unicode instead of ASCII.
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It has more bits / possible combinations Can represent more characters/emojis Can represent more worldwide languages (2 marks - 1 per bullet)Mark yourself: how many marks did you get?/ 2 - Question 4H446/012 marks
Explain one drawback of using Unicode instead of ASCII.
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Each character is stored using more bits Increases file size (2 marks - 1 per bullet)Mark yourself: how many marks did you get?/ 2 - Question 5H446/01 · June 20241 mark
Convert the denary number -124 into an 8-bit two's complement binary number.
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1000 0100 (1 mark)Mark yourself: how many marks did you get?/ 1 - Question 6H446/01 · June 20241 mark
State one other way to represent negative binary numbers.
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Sign and magnitude (or One's complement) (1 mark)Mark yourself: how many marks did you get?/ 1 - Question 7H446/01 · June 20242 marks
Convert the denary number 298 into hexadecimal.
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12A (2 marks - 1 for 12, 1 for A)Mark yourself: how many marks did you get?/ 2 - Question 8H446/01 · June 20243 marks
The binary number 10011101 0110 is stored in normalised floating point form with an 8-bit mantissa and a 4-bit exponent both in two's complement. Convert this into denary.
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Converting exponent to 6 Converting mantissa to 1001110.1 (moving binary point 6 to right) -49.5 (denary answer) (3 marks - 1 per bullet)Mark yourself: how many marks did you get?/ 3 - Question 9H446/013 marks
Using the binary value 1001 1101, convert this into: a positive denary number, a negative denary number using two's complement, and a hexadecimal value.
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Positive denary: 157 Negative denary (two's complement): -99 Hexadecimal: 9D (3 marks - 1 per answer)Mark yourself: how many marks did you get?/ 3 - Question 10H446/019 marks
Discuss the different types of data that can be stored in binary and why computer systems store data in binary format.
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Levels of response question (9 marks) AO1 Types of data: Numeric, Alphanumeric/text/characters/symbols, Sound, Images, Video AO2 Examples: Text - ASCII/Unicode character sets; Numbers - sign and magnitude, two's complement, floating point; Images - pixels with binary colour values; Sound - sampled as binary numbers AO3 Reasons: Computers use binary logic for on/off states; Computer systems based on switches/transistors; Binary is high tolerance; Two states easily translate to binary valuesMark yourself: how many marks did you get?/ 9 - Question 11H446/01 · June 20231 mark
Convert the denary number 189 to hexadecimal.
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BD (1 mark)Mark yourself: how many marks did you get?/ 1 - Question 12H446/01 · June 20232 marks
Convert the denary number -107 to an 8-bit binary number using sign and magnitude, then using two's complement.
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Sign and magnitude: 1110 1011 Two's complement: 1001 0101 (2 marks - 1 per answer)Mark yourself: how many marks did you get?/ 2 - Question 13H446/01 · June 20231 mark
Give one advantage of storing values using two's complement instead of sign and magnitude.
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Calculations are more easily performed on two's complement Two's complement allows for a larger range of numbers to be stored No additional hardware is required in two's complement Two's complement has only one representation for 0 (1 mark for any valid point)Mark yourself: how many marks did you get?/ 1 - Question 14H446/01 · June 20234 marks
Show how the denary value -15.75 can be represented as a normalised floating point binary number using 8 bits for the mantissa and 4 bits for the exponent.
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-15.75 is 10000.01 in fixed point two's complement Binary point moved 4 places left Mantissa: 1000 0010 Exponent: 0100 (4 marks - 1 per bullet)Mark yourself: how many marks did you get?/ 4 - Question 15H446/01 · June 20232 marks
Complete the sentences: Increasing the number of bits used for the mantissa increases the ______ of the number. Increasing the number of bits used for the exponent increases the ______ of the number.
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Mantissa: precision / accuracy Exponent: range / size / magnitude (2 marks - 1 per blank)Mark yourself: how many marks did you get?/ 2 - Question 16H446/011 mark
State the benefit of using a normalised form when representing data as a floating point number.
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Allows for more accuracy/precision from the given number of bits The representation of each binary value is unique (1 mark)Mark yourself: how many marks did you get?/ 1 - Question 17H446/01 · June 20172 marks
Describe what is meant by the term 'character set'.
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List/mapping of characters that can be understood by the hardware/software/computer Each character is given a unique binary/numeric code that is stored instead of the character (2 marks - 1 per bullet)Mark yourself: how many marks did you get?/ 2 - Question 18H446/012 marks
Convert the hexadecimal number 66 into a denary number.
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102 (6x16 + 6 = 102) (2 marks - 1 for method, 1 for answer)Mark yourself: how many marks did you get?/ 2 - Question 19H446/012 marks
State two reasons why a programmer would prefer to use hexadecimal numbers rather than binary numbers.
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Hexadecimal values are shorter than binary as 4 bits/nibble can be represented by one hex character Hexadecimal values are faster/more reliable to communicate/enter/write down/read (2 marks - 1 per bullet)Mark yourself: how many marks did you get?/ 2 - Question 20H446/011 mark
State why computer systems store data in binary.
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Computers use binary logic for on/off or 1/0 states Computer systems are based on switches/transistors Binary is high tolerance (1 mark for any valid point)Mark yourself: how many marks did you get?/ 1 - Question 21H446/01 · June 20221 mark
Give one similarity between ASCII and Unicode.
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Both use binary to represent characters // both are character sets The first 7/8 bits of Unicode is the same as ASCII (overlaps) (1 mark)Mark yourself: how many marks did you get?/ 1 - Question 22H446/01 · June 20222 marks
Give two differences between ASCII and Unicode.
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ASCII has fewer characters (128/256) // Unicode has more characters ASCII is 7/8 bits whereas Unicode can be larger (16/32 bits) / can have variable sized characters ASCII limited to Latin/English/European characters whereas Unicode can represent other symbols (e.g. Chinese/Cyrillic/Emojis) (2 marks - 1 per difference)Mark yourself: how many marks did you get?/ 2
- 1Two's complement: Use the invert method - keep bits unchanged from the right up to and including the first 1, then invert all bits to the left; Range: -128 to +127 (8-bit)
- 2Binary addition: Show carries; 1+1=0 carry 1, 1+1+1=1 carry 1
- 3Hexadecimal: Binary↔Hex (4-bit groups); Denary→Hex (divide by 16)
- 4Floating point: Sign bit + Mantissa + Exponent; Normalised: starts with 01 or 10
- 5Character sets: ASCII (7-bit, 128 chars), Unicode (140,000+ chars, all languages)
- •Practice answering questions under timed conditions
- •Check your answers against the mark scheme carefully
- •Focus on understanding the marking points, not just memorising answers
- •Review past paper questions from multiple years to spot patterns