BREAKING
Student's code works, nobody knows why, including student★Local teen writes pseudocode, accidentally invents a language★Binary joke told in class, exactly 10 students laugh★
  1. Home
  2. A Level
  3. Computer Science
  4. OCR
  5. Converting between denary and hexadecimal

OCR A Level Computer Science

Topic questions Memory and storage Converting between denary & hexadecimal

Converting between denary & hexadecimal

6 questions · 81 marks · about 1.5 hours

Converting between denary and hexadecimal questions

OCR H446 Converting between denary and hexadecimal 6 questions

Computer systems June 2025, Question 3 14 marks

(a)
(a)(i)

Convert the denary number 189 into an 8-bit binary number.

[1]
Reveal mark scheme Mark scheme for question 3(a)(i)
(a)(ii)

Convert the denary number 189 into a hexadecimal value.

[1]
Reveal mark scheme Mark scheme for question 3(a)(ii)
(a)(iii)

Convert the hexadecimal value E4 into a denary number.

[1]
Reveal mark scheme Mark scheme for question 3(a)(iii)
(b)

Explain the effect that a right shift of three places will have on a positive binary number.

[2]
Reveal mark scheme Mark scheme for question 3(b)
(c)

Show the subtraction of these two floating point binary numbers.

Both numbers are stored in a normalised floating point format, using 6 bits for the mantissa and 4 for exponent.

You should show your result in the same format.

Show your working out.

011010 0011 – 010010 0010

Final 6-bit mantissa........

Final 4-bit exponen t........

[6]
Reveal mark scheme Mark scheme for question 3(c)
(d)
(d)(i)

Show the result of applying a bitwise AND mask of 1010 1110 to the byte 1010 0011.

Question 3, shown as an image
[2]
Reveal mark scheme Mark scheme for question 3(d)(i)
(d)(ii)

State the purpose of the bitwise AND mask.

[1]
Reveal mark scheme Mark scheme for question 3(d)(ii)

Computer systems June 2024, Question 4 13 marks

(a)

Two’s complement can be used to represent negative binary numbers.

(a)(i)

Convert the denary number-124 into an 8-bit two’s complement binary number.

[1]
Reveal mark scheme Mark scheme for question 4(a)(i)
(a)(ii)

State one other way to represent negative binary numbers.

[1]
Reveal mark scheme Mark scheme for question 4(a)(ii)
(b)

Convert the denary number 298 into hexadecimal.

[2]
Reveal mark scheme Mark scheme for question 4(b)
(c)

The binary number 10011101 0110 is stored in normalised floating point form with an 8-bit mantissa and a 4-bit exponent both written in two’s complement.

Convert this binary number into denary.

You must show your working.

[3]
Reveal mark scheme Mark scheme for question 4(c)
(d)

The binary number 00001011 0111 is represented in unnormalised floating point form with an 8-bit mantissa and a 4-bit exponent both written in two’s complement.

Convert this binary number into a normalised floating point binary number, represented using an 8-bit mantissa and 4-bit exponent format.

You must show your working.

[4]
Reveal mark scheme Mark scheme for question 4(d)
(e)
Figure for question 4
[2]
Reveal mark scheme Mark scheme for question 4(e)

Computer systems June 2023, Question 3 14 marks

(a)(i)

Convert the denary number 189 to hexadecimal.

[1]
Reveal mark scheme Mark scheme for question 3(a)(i)
(a)(ii)

Convert the unsigned binary number 1010101111 to hexadecimal.

[1]
Reveal mark scheme Mark scheme for question 3(a)(ii)
(b)

Negative binary values can be represented using either sign and magnitude or two’s complement.

(b)(i)

Convert the denary number-107 to an 8-bit binary number using sign and magnitude.

[1]
Reveal mark scheme Mark scheme for question 3(b)(i)
(b)(ii)

Convert the denary number-107 to an 8-bit binary number using two’s complement.

[1]
Reveal mark scheme Mark scheme for question 3(b)(ii)
(b)(iii)

Give one advantage of storing values using two’s complement instead of sign and magnitude.

[1]
Reveal mark scheme Mark scheme for question 3(b)(iii)
(c)

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.

You must show your working.

[4]
Reveal mark scheme Mark scheme for question 3(c)
(d)

The normalised floating point binary number 0100 1110 is stored using 4 bits for the mantissa and 4 bits for the exponent, both in two’s complement.

Convert this number to denary.

You must show your working.

[3]
Reveal mark scheme Mark scheme for question 3(d)
(e)

Complete each of the following sentences relating to the storage of floating point binary numbers with an appropriate word.

Increasing the number of bits used for the mantissa increases the........ of the number that can be stored.

Increasing the number of bits used for the exponent increases the........ of the number that can be stored.

[2]
Reveal mark scheme Mark scheme for question 3(e)

Computer systems November 2020, Question 3 14 marks

(a)(i)

Convert the denary number −119 to an 8-bit binary number with two’s complement representation.

[1]
Reveal mark scheme Mark scheme for question 3(a)(i)
(a)(ii)

Convert the unsigned binary number 1101101 to hexadecimal.

[1]
Reveal mark scheme Mark scheme for question 3(a)(ii)
(a)(iii)

Convert the denary number 171 to hexadecimal.

[1]
Reveal mark scheme Mark scheme for question 3(a)(iii)
(a)(iv)

Convert the hexadecimal number A6 to binary.

[2]
Reveal mark scheme Mark scheme for question 3(a)(iv)
(b)

Show how the denary value −9.125 can be represented in normalised floating point format, using 8 bits for the mantissa and 4 bits for the exponent, both in two’s complement.

[5]
Reveal mark scheme Mark scheme for question 3(b)
(c)(i)

Show the result of applying an XOR mask of 1100 0111 to the byte 0101 1101.

Byte 0101 1101

Question 3, shown as an image
[2]
Reveal mark scheme Mark scheme for question 3(c)(i)
(c)(ii)

Describe a mask that could be applied to an 8-bit number to ensure that:

• the most significant bit is always set to 1

• all other bits remain unchanged.

[2]
Reveal mark scheme Mark scheme for question 3(c)(ii)

Computer systems June 2019, Question 10 14 marks

(a)

Show how the binary number 01011110 is represented in hexadecimal.

[1]
Reveal mark scheme Mark scheme for question 10(a)
(b)

Show how the hexadecimal number 9B is represented in denary.

[2]
Reveal mark scheme Mark scheme for question 10(b)
(c)

Show how the denary number −87 is represented in sign and magnitude binary.

[2]
Reveal mark scheme Mark scheme for question 10(c)
(d)

Complete the following binary subtraction. Show your working.

Figure for question 10
[2]
Reveal mark scheme Mark scheme for question 10(d)
(e)

The floating point binary number 010011 011 consists of a 6-bit mantissa and 3-bit exponent, both represented in two’s complement. Convert the number to denary, showing your working.

[3]
Reveal mark scheme Mark scheme for question 10(e)
(f)

Show the denary number −5.25 in floating point binary form representing the mantissa and exponent in two’s complement, using as few bits as possible. Show your working.

[4]
Reveal mark scheme Mark scheme for question 10(f)

Computer systems June 2017, Question 6 12 marks

(a)(i)

Convert the denary number 188 to an unsigned 8-bit binary number.

[1]
Reveal mark scheme Mark scheme for question 6(a)(i)
(a)(ii)

Convert the denary number 188 to hexadecimal.

[1]
Reveal mark scheme Mark scheme for question 6(a)(ii)
(b)(i)

Convert the denary number −44 to an 8-bit binary number with sign and magnitude representation.

[1]
Reveal mark scheme Mark scheme for question 6(b)(i)
(b)(ii)

Convert the denary number −44 to an 8-bit binary number with two’s complement representation.

[1]
Reveal mark scheme Mark scheme for question 6(b)(ii)
(c)

Explain how, using bit shift, the unsigned binary number 00101100 can be divided by 4.

[2]
Reveal mark scheme Mark scheme for question 6(c)
(d)

Demonstrate subtraction on the two numbers below, both stored in normalised floating point format, using 6 bits for their mantissa and 4 for their exponent. Show the result in the same format. Show your working.

010010 0100 - 010010 0010

[6]
Reveal mark scheme Mark scheme for question 6(d)

Report a problem with a question on this page
What is wrong?

Goes to whoever maintains the question split. No account needed and nothing is published on this page.

Memes

Certified Computer Science memes. Peer-reviewed by nobody.

Laugh now. Cry in the exam hall later. Then come back and do a past paper.

Write a proper algorithm
Write ‘sort it’ and leave
Me on the 6-mark pseudocode question
Debugging with print statements
Using a trace table
Knowing the difference between = and ==
Explaining recursion by explaining recursion
Code enlightenment, ranked

Mum 💖

can you fix the wifi since you do computers 🥰

that's not what computer science is

so that's a no then

📱 Screen time this week · Discord8h 2m

Turned it off and on again

Computer Science starter pack

Laptop with 47 tabs openPython error on line 1Counting binary on fingersThis website
Compiled with zero errors