A Level Computer Science (A2) chapter 1: Data Representation MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
76 exam-style questions on Data Representation, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Floating-point numbers, representation and manipulation27 questions
Ten Data Representation questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. In a sequential file, how are the records arranged?
A
in the order in which they were created
B
in the order in which they were last read
C
at addresses calculated by a hashing algorithm
D
in order of a key field
Show answer
Answer: D. A sequential file keeps the records sorted on a key field, such as a customer number. A file in order of creation is serial.
2. Which statement about overflow and underflow in a floating-point system is correct?
A
increasing the mantissa bits makes both less likely
B
they can only occur when a mantissa is negative
C
increasing the exponent bits makes both less likely
D
they can only occur when numbers are not normalised
Show answer
Answer: C. Overflow and underflow are limits of the exponent's range, so more exponent bits widen the range and make them less likely. More mantissa bits improve precision, not range.
3. In a floating-point number, what does the exponent represent?
A
the number of digits after the binary point
B
the sign of the whole of the number that is being stored
C
the power of 2 by which the mantissa is multiplied
D
the number of bits that are used in the mantissa
Show answer
Answer: C. A floating-point value is mantissa × 2exponent. The exponent, in two's complement, moves the binary point of the mantissa left or right.
4. A program stores a student's name, date of birth and form group as one item. Which user-defined data type is the most appropriate?
A
a set
B
a record
C
an enumerated type
D
a pointer
Show answer
Answer: B. The three values have different types and belong to one student, which is exactly what a record is for. A set has one type and no order; an enumerated type is a list of named values.
5. The following statements are run. SEEK "Stock.dat", 7 GETRECORD "Stock.dat", ItemWhat is stored in Item?
A
the first record in the file
B
the record whose key is 7
C
the record at address 7 of the file
D
the last record in the file
Show answer
Answer: C. SEEK moves the file pointer to the given address, and GETRECORD reads the record at that address. It is the address, not the key, that is used.
6. An 8-bit mantissa (two's complement, binary point after the first bit) is followed by a 4-bit exponent (two's complement). Mantissa 01101000, exponent 0011. What is the denary value?
A
0.8125
B
4.875
C
13
D
6.5
Show answer
Answer: D. The mantissa is 0.1101 in binary = 0.8125 and the exponent is +3, so the value is 0.8125 × 23 = 6.5. The value 0.8125 forgets the exponent.
7. A random file has 200 record positions numbered 0 to 199. Which hash function always gives a valid address for a positive integer key?
A
Key DIV 200
B
Key MOD 200
C
Key MOD 201
D
Key * 200
Show answer
Answer: B. The remainder after dividing by 200 is always from 0 to 199. Key MOD 201 can produce 200, which is outside the file, and DIV or multiplication can produce much larger numbers.
8. What is the main reason for normalising floating-point numbers?
A
to give the greatest precision for the mantissa bits
B
to make the exponent as large as it can possibly be made
C
to allow negative numbers to be stored at all
D
to make every value use the same number of bits
Show answer
Answer: A. Normalisation removes wasted leading bits from the mantissa, so all the mantissa bits carry significant digits. It also gives just one representation for each value.
9. An 8-bit two's complement mantissa (binary point after the first bit) is followed by a 4-bit two's complement exponent. Mantissa 10110000, exponent 0010. What is the denary value?
A
-2.5
B
-0.625
C
-1.5
D
5.5
Show answer
Answer: A. The mantissa 1.0110000 = −1 + 0.375 = −0.625, and the exponent is +2, so the value is −0.625 × 4 = −2.5. Treating the sign bit as a plain sign would give −1.5.
10. An 8-bit two's complement mantissa (binary point after the first bit) has a 4-bit two's complement exponent. What is the largest positive number that can be stored?
A
128
B
255
C
15.9375
D
127
Show answer
Answer: D. The largest mantissa is 01111111 = 127/128, and the largest exponent is 0111 = +7, so the value is 127/128 × 128 = 127. The exponent's maximum is 7, not 15.
76, each with the answer and a short explanation, across 3 topics: User-defined data types, File organisation and access, Floating-point numbers, representation and manipulation. Every chapter test draws ten of them, so you can take it many times.
Is the A Level Computer Science (A2) chapter 1 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
