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Edexcel GCSE Computer Science (1CP2) Exam Questions

Build a practice paper from 514 exam-style questions, each with its mark scheme and example answers. Print it, or answer it on paper and then open the mark schemes. Or browse the questions by topic.

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5 questions · 11 marks

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1Convert2 marksDenary to Binary Conversion Swap Remove

Computers manipulate binary patterns.

Convert the denary number 184 to 8-bit binary.

[2 marks]
Mark scheme

Award one mark for each correct nibble in the correct order:

  • 1011 (1)
  • 1000 (1)

0 marks if the response is not 8-bit binary.

Example answers and how they were marked
Full marks2/2

1011 1000

Why: 184 = 128 + 32 + 16 + 8: both nibbles are correct (2).

Some marks1/2

1011 1001

Why: Converts 185 instead (a slip in adding up the place values). The first nibble is correct (1); the second is not.

No marks0/2

0001 1101

Why: The bits are written in reverse, smallest place value first. Neither nibble is correct.

2Convert2 marksDenary to Binary Conversion Swap Remove

Computer systems manipulate bit patterns.

Convert the denary number 140 to 8-bit binary.

[2 marks]
Mark scheme

Award one mark for each correct nibble in the correct order:

  • 1000 (1)
  • 1100 (1)

0 marks if the response is not 8-bit binary.

Example answers and how they were marked
Full marks2/2

1000 1100

Why: 140 = 128 + 8 + 4: both nibbles are correct (2).

Some marks1/2

1000 1101

Why: Converts 141 instead (a slip in adding up the place values). The first nibble is correct (1); the second is not.

No marks0/2

0011 0001

Why: The bits are written in reverse, smallest place value first. Neither nibble is correct.

3Convert2 marksDenary to Negative Binary Conversion Swap Remove

Binary patterns can represent numbers.

Convert the 8-bit binary two's complement pattern 1111 1001 to denary.

[2 marks]
Mark scheme

Award one mark for each of:

  • − (negative sign) (1)
  • 7 (1)

The correct answer is −7

Example answers and how they were marked
Full marks2/2

−7

Why: The left-hand bit is worth −128: −128 + 121 = -7. Sign (1) and value (1).

Some marks1/2

7

Why: The value is right (1) but the minus sign is missing.

No marks0/2

249

Why: Reads it as an unsigned number, so neither the sign nor the value is right.

4Calculate2 marksBinary Shifts Swap Remove

Computer systems manipulate bit patterns.

Complete the table with the result of applying the shift to the binary pattern.

[2 marks]
Binary patternShift8-bit binary result
0011 0100Logical shift left by 3
Mark scheme

Award one mark for each correct nibble in the correct order:

  • 1010 (1)
  • 0000 (1)

0 marks if the response is not 8-bit binary.

Example answers and how they were marked
Full marks2/2

1010 0000

Why: Every bit moves 3 places left, with 0s in from the right: both nibbles are correct (2).

Some marks1/2

1101 0000

Why: Shifts 2 places instead of 3. The second nibble is correct (1); the first is not.

No marks0/2

0000 0110

Why: Shifts the bits the wrong way. Neither nibble is correct.

5Calculate3 marksAdding Binary Numbers Swap Remove

Computers manipulate binary patterns.

(a)

Complete the table to show the 8-bit result of the binary addition.

[2 marks]
1286432168421
10111001
10111100
Mark scheme

Award one mark for each correct nibble in the correct order:

  • 0111 (1)
  • 0101 (1)

0 marks if the response is not 8-bit binary.

Ignore a carry shown beyond the eighth bit.

Example answers and how they were marked
Full marks2/2

0111 0101

Why: 185 + 188 = 373, which needs 9 bits; the 8 bits that are kept are both correct (2).

Some marks1/2

0000 0101

Why: Forgets to carry the 1s. The second nibble is correct (1); the first is not.

No marks0/2

1011 1101

Why: Never carries. Neither nibble is correct.

(b)

State the name of the error that occurs when this addition is carried out.

[1 mark]
Mark scheme

Award one mark for:

  • overflow (error) (1)
Example answers and how they were marked
Full marks1/1

Overflow

Why: The result needs more bits than are available (1).

No marks0/1

Underflow

Why: A near miss: the result is too big for 8 bits, not too small.

No marks0/1

A syntax error

Why: A syntax error is a mistake in a program's code, not in arithmetic.

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