Oxford Cambridge and RSA
GCSE (9-1) Computer Science
Computer Systems
J277/01
Topic: Unit 1.2 Binary Arithmetic & Shifts
Time allowed: 20 minutes
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INSTRUCTIONS
Use black ink.
Answer all the questions.
INFORMATION
The total mark for this paper is 16.
The marks for each question are shown in brackets [ ].
Turn over
1
Add the following two 8-bit binary numbers.
Show your working.
[2]
0 0 1 1 0 1 0 0
+ 0 0 0 1 1 0 1 1
_______________
Working:
Answer:
2
Add the following two 8-bit binary numbers.
Show your working.
1 1 1 1 0 0 0 1
+ 0 0 0 0 1 1 1 1
_______________
Working:
(a) Write the 8-bit binary result.
[2]
Answer:
(b) State the name of the error that has occurred in this calculation.
[1]
Turn over
3
Binary shifts are used to perform simple multiplication and division.
(a) Perform a Binary Shift Left of 2 places on the number: 0000 1110.
[1]
Answer:
(b) Explain the mathematical effect of performing a Left Shift of 1 place on a binary number.
[1]
(c) Describe the binary shift required to divide any binary number by 4.
[1]
4
A student performs a Right Shift of 1 place on the binary number: 0001 0101 (Denary 21).
(a) Write the result of this shift.
[1]
Answer:
(b) The mathematically correct answer to 21 ÷ 2 is 10.5.
Explain why the result of your binary shift in part (a) is not exactly 10.5.
[2]
Turn over
5
Perform a binary shift to multiply the number 0000 0101 by 8.
Show the resulting 8-bit binary number.
[2]
Answer:
6
Explain what happens to the Most Significant Bit (MSB) during a Left Shift of 1 place if the MSB is already a 1.
(e.g., shifting 1000 0000 to the left).