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Edexcel GCSE Computer Science (1CP2) Exam Questions

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9 questions · 18 marks

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1Convert2 marksBinary to Hexadecimal Conversion Swap Remove

Binary, denary and hexadecimal patterns represent numbers.

Convert the binary pattern 1100 1010 to hexadecimal.

[2 marks]
Mark scheme

Award one mark for each correct digit in the correct position:

  • C (1)
  • A (1)

Answer: CA

Example answers and how they were marked
Full marks2/2

CA

Why: Each nibble is one hexadecimal digit: 1100 = C, 1010 = A: both digits are correct (2).

Some marks1/2

C10

Why: One digit is correct (1), but the second is written as 10 in denary instead of A.

No marks0/2

AC

Why: The digits are the wrong way round, so neither is in the correct position.

2Explain2 marksBinary and Hexadecimal Basics Swap Remove

A traffic light controller uses a 5-bit binary pattern to store the state of its lights.

Explain why this pattern can represent a maximum of 32 different states.

[2 marks]
Mark scheme

Award up to two marks for a linked explanation such as:

  • Each bit has two possible values, 0 and 1 (1) so the five bits give 2 × 2 × 2 × 2 × 2/2^5 = 32 different combinations/states (1)
  • Because each of the five bits can be either 0 or 1 (1) there are 2^5/2 × 2 × 2 × 2 × 2 = 32 different combinations/states (1)
  • Each extra bit doubles the number of combinations/states (1) so five bits give 2^5 = 32 states (1)

For both marks, the expansion must follow/associate with the statement.

Do not award a response that only repeats the 32 states given in the question, such as 'it can represent 32 states' or '2^5 = 32', without a reason about each bit having two possible values.

Do not accept 2 × 5 = 10 as the calculation; the number of states doubles with each extra bit.

Do not accept 31/0 to 31 as the number of states; 31 is the largest value five bits can store, not the number of states.

Example answers and how they were marked
Full marks2/2

There are 32 different states because each of the 5 bits has two possible values, 0 and 1, so the number of combinations is 2 × 2 × 2 × 2 × 2 = 32.

Why: Point that each bit has two possible values, 0 and 1 (1), linked to the calculation 2 × 2 × 2 × 2 × 2 = 32 states (1).

Some marks1/2

Each bit has two possible values, 0 and 1.

Why: Gives the point that each bit has two possible values (1) but does not link it to 2^5 = 32, so the second mark is not earned.

No marks0/2

It can represent 32 states because the highest number it can store is 31.

Why: Only repeats the 32 states from the question and gives the common misconception that 31 is the number of states; there is no reason about each bit having two possible values, so no marks.

3Convert2 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.

4Convert2 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.

5Convert2 marksDenary to Negative Binary Conversion Swap Remove

Computer systems manipulate bit patterns.

Convert the denary number -48 to 8-bit binary using two's complement.

[2 marks]
Mark scheme

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

  • 1101 (1)
  • 0000 (1)

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

Example answers and how they were marked
Full marks2/2

1101 0000

Why: 48 is 00110000; flip the bits (11001111) and add 1: both nibbles are correct (2).

Some marks1/2

1011 0000

Why: Uses sign and magnitude (a 1 in front of 48) instead of two's complement. The second nibble is correct (1); the first is not.

No marks0/2

1100 1111

Why: Flips the bits of 48 but doesn't add 1. Neither nibble is correct.

6Convert2 marksDenary to Negative Binary Conversion Swap Remove

Computer systems manipulate bit patterns.

Convert the 8-bit binary two's complement pattern 1000 0111 to denary.

[2 marks]
Mark scheme

Award one mark for each of:

  • − (negative sign) (1)
  • 121 (1)

The correct answer is −121

Example answers and how they were marked
Full marks2/2

−121

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

Some marks1/2

121

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

No marks0/2

135

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

7Convert2 marksDenary to Negative Binary Conversion Swap Remove

Computer systems manipulate bit patterns.

Convert the 8-bit binary two's complement pattern 1100 1011 to denary.

[2 marks]
Mark scheme

Award one mark for each of:

  • − (negative sign) (1)
  • 53 (1)

The correct answer is −53

Example answers and how they were marked
Full marks2/2

−53

Why: The left-hand bit is worth −128: −128 + 75 = -53. Sign (1) and value (1).

Some marks1/2

53

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

No marks0/2

203

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

8Calculate2 marksAdding Binary Numbers Swap Remove

Computers manipulate binary patterns.

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

[2 marks]
1286432168421
10010101
01001111
Mark scheme

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

  • 1110 (1)
  • 0100 (1)

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

Example answers and how they were marked
Full marks2/2

1110 0100

Why: 149 + 79 = 228, carrying where a column adds to 2: both nibbles are correct (2).

Some marks1/2

1110 0101

Why: A slip in the last bit. The first nibble is correct (1); the second is not.

No marks0/2

1101 1111

Why: Writes 1 in every column with a 1 and never carries. Neither nibble is correct.

9Calculate2 marksBinary Shifts Swap Remove

Binary, denary and hexadecimal patterns represent numbers.

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

[2 marks]
Binary patternShift8-bit binary result
1010 1100Arithmetic shift right by 1
Mark scheme

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

  • 1101 (1)
  • 0110 (1)

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

Example answers and how they were marked
Full marks2/2

1101 0110

Why: Every bit moves 1 place right, with copies of the sign bit (1) in from the left: both nibbles are correct (2).

Some marks1/2

0101 0110

Why: Fills the gap on the left with 0s, as a logical shift would, instead of copying the sign bit. The second nibble is correct (1); the first is not.

No marks0/2

0101 1000

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

Questions by topic

2.1 Binary

Build a paper on this topic 58
Adding Binary Numbers 6 questions Binary and Hexadecimal Basics 10 questions Binary Shifts 6 questions Binary to Denary Conversion 6 questions Binary to Hexadecimal Conversion 6 questions Denary to Binary Conversion 6 questions Denary to Hexadecimal Conversion 6 questions Denary to Negative Binary Conversion 6 questions Hexadecimal to Binary Conversion 6 questions

2.2 Data representation

Build a paper on this topic 56
Character Sets 18 questions Images 19 questions Sound 19 questions

2.3 Data storage and compression

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Compression 18 questions Units & Conversion 6 questions

3.1 Hardware

Build a paper on this topic 77
Embedded Systems 17 questions Fetch Decode Execute Cycle 15 questions Primary Memory 15 questions Secondary Memory 15 questions Stored Program Computers 15 questions

3.2 Software

Build a paper on this topic 124
File Management 18 questions Memory Management 16 questions Peripheral Management 11 questions Process Management 12 questions Purpose & Function of Operating Systems 17 questions Software Basics 13 questions User Management 18 questions Utility Software 19 questions

3.3 Programming languages

Build a paper on this topic 37
Low and High Level Languages 19 questions Translators 18 questions

4.1 Networks

Build a paper on this topic 138
Addressing 16 questions LANs & WANs 16 questions Network Speed 5 questions Packet Switching 16 questions Protocols & Layers 17 questions The Internet 16 questions Topologies 17 questions Wired Connections 17 questions Wireless Connections 18 questions

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