GCSE COMPUTER SCIENCE MARK SCHEME – JUNE 2024 (J277/01)

GCSE COMPUTER SCIENCE
MARK SCHEME – JUNE 2024
(J277/01)
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, GCSE Computer Science Mark Scheme – June 2024 (J277/01)

General Information

• Exam Board: OCR (Oxford Cambridge and RSA Examinations)

• Qualification: GCSE Computer Science

• Paper: J277/01 (Computer Systems)

• Mark Scheme Release: June 2024




Question 1: Binary & Hexadecimal

1(a): Convert 8-bit binary to denary.

• Example: 111100001111000011110000

o Calculation: 1×27+1×26+1×25+1×24+0×23+0×22+0×21+0×20=128+64+3
2+16+0+0+0+0=2401 \times 2^7 + 1 \times 2^6 + 1 \times 2^5 + 1 \times
2^4 + 0 \times 2^3 + 0 \times 2^2 + 0 \times 2^1 + 0 \times 2^0 = 128 + 64
+ 32 + 16 + 0 + 0 + 0 + 0 =
2401×27+1×26+1×25+1×24+0×23+0×22+0×21+0×20=128+64+32+16+0+0
+0+0=240

1(b): Define terms.

• Smallest 4-bit number = 000000000000 (denary: 0)

• Largest 4-bit number = 111111111111 (denary: 15)

• 8-bit binary
range: 000000000000000000000000 to 111111111111111111111111 (denary: 0
to 255).

1(c): Perform binary addition (show carries).

• Example: 1011+11011011 + 11011011+1101

Copy 1 (carry)

1011

+ 1101

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