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Edexcel GCSE Computer Science (1CP2) Exam Questions

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7 questions · 22 marks

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1Multiple choice1 markCharacter Sets Swap Remove

Characters are encoded using 7-bit ASCII.

Identify the number of different characters that can be represented using 7-bit ASCII.

[1 mark]
  • A64
  • B127
  • C128
  • D256
Mark scheme
  • C 128 (1)
  • The only correct answer is C. The correct answer is 128.
  • A is not correct because 6 bits give only 64 different combinations
  • B is not correct because 127 is the largest 7-bit value, not the number of characters that 7 bits can represent
  • D is not correct because 256 characters need 8 bits, as used by 8-bit extended ASCII
Example answers and how they were marked
Full marks1/1

C 128

Why: Selects the only correct option (1): 7 bits give 2 to the power of 7, which is 128 different characters.

No marks0/1

D 256

Why: Near miss scoring 0: 256 is the number of characters that 8 bits give in extended ASCII, not 7-bit ASCII.

No marks0/1

B 127

Why: Misconception scoring 0, the off-by-one error the examiners' report describes: 127 is the largest 7-bit value, but 7 bits give 128 different characters.

2Short recall2 marksStored Program Computers Swap Remove

Computers use the von Neumann stored program concept.

Define the term stored program concept.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • Program instructions are stored in main memory/RAM (1)
  • The data used by the program is stored in main memory/RAM (1)
  • The CPU fetches/reads instructions from main memory to execute them (1)
  • The program can be run without the instructions being input again (1)

Allow 'the program is stored in memory' for one mark.

Do not accept answers about programs being stored on secondary storage, such as a hard disk or USB memory stick.

Do not accept answers that only describe the von Neumann architecture (e.g. having a CPU and memory) without stating that instructions are stored in main memory.

Example answers and how they were marked
Full marks2/2

Both the program instructions and the data the program uses are held in the same main memory, and the CPU fetches these instructions from memory to execute them.

Why: Instructions stored in main memory (1) and the CPU fetches instructions from memory to execute them (1).

Some marks1/2

Program instructions are stored in main memory.

Why: Instructions stored in main memory (1). No second point about data being stored in the same memory or about the CPU fetching instructions.

No marks0/2

The program is saved on the hard disk so that it can be loaded into RAM when the user runs it.

Why: A near-miss about secondary storage, which the mark scheme says not to accept; the stored program concept is about instructions being held in main memory.

3Short recall2 marksUnits & Conversion Swap Remove

Data storage is measured in binary multiples.

Define the term bit.

[2 marks]
Mark scheme

Award one mark for any of the following up to a maximum of two marks:

  • A binary digit (1)
  • Has the value 0 or 1 (1)
  • The smallest unit of data storage (1)
  • A single 0 or 1 (1)

Allow binary digit/binary place value for binary digit

Allow a single binary digit for a single 0 or 1

Do not accept a group of 8 bits/half a nibble of 4 bits, which describe a byte or a nibble

Do not accept a binary number/binary on its own

Example answers and how they were marked
Full marks2/2

A binary digit that can have the value 0 or 1.

Why: A binary digit (1) and has the value 0 or 1 (1).

Some marks1/2

It is the smallest unit of data storage.

Why: Smallest unit of data storage (1), but does not state that it is a binary digit or that it has the value 0 or 1.

No marks0/2

A group of 8 bits.

Why: Describes a byte, not a bit; no creditworthy point and named in the Do not accept line.

4Describe2 marksUtility Software Swap Remove

A student has a large number of photographs stored on a computer.

Describe the purpose of data compression software.

[2 marks]
Mark scheme

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

  • Makes a file/files smaller (1) so less storage space is needed on the disk (1)
  • Reduces the size of the data (1) so it takes less time to upload/download/transfer the file (1)
  • Compresses files/folders into a single file (1) so an attachment is under the size limit for email (1)
  • Reduces the size of the files (1) so more of them fit onto a storage device/backup media (1)

Do not accept 'it compresses the files' on its own, as this repeats the question.

Do not accept responses about protecting files from malware/viruses or about deleting files.

Example answers and how they were marked
Full marks2/2

It makes the files smaller (1) so that they use less storage space on the computer and more of them fit on the disk (1).

Why: The point (1) and a linked development giving the benefit (1).

Some marks1/2

It makes files smaller.

Why: This is the point (1) but there is no development of what the smaller size leads to, so only one mark.

No marks0/2

It protects the files from viruses so that they cannot be damaged.

Why: This describes anti-malware software, which the mark scheme does not accept; no creditworthy point is made.

5Calculate3 marksAdding Binary Numbers Swap Remove

Binary patterns can represent numbers.

(a)

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

[2 marks]
1286432168421
11011011
11011100
Mark scheme

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

  • 1011 (1)
  • 0111 (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

1011 0111

Why: 219 + 220 = 439, which needs 9 bits; the 8 bits that are kept are both correct (2).

Some marks1/2

0000 0111

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

No marks0/2

1101 1111

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.

6Discuss6 marksSoftware Basics Swap Remove

A dental practice has a network of computers used by receptionists, dentists and managers. Patient records are stored in shared folders and staff have different levels of access.

Discuss how the operating system's file management and user management support the dental practice.

Your answer should consider:

  • file management
  • user management
[6 marks]
Mark scheme

Indicative content

File management

  • The operating system organises the practice's patient records into folders, so staff can find a patient's record quickly during an appointment.
  • It carries out file operations such as saving, moving, renaming and deleting, so a dentist can save updated notes to the correct record.
  • It sets permissions on shared folders and files, so that only authorised staff, such as dentists, can open a patient's clinical records; this reduces the risk of confidential records being seen by the wrong staff.
  • It can give read-only access to some files, so receptionists can view appointment details but cannot change clinical notes.
  • It shows the size of files and the free space on the practice's shared storage, so managers can see when more storage is needed for records.

User management

  • The operating system creates a user account for each member of staff, with a username and password, so that each person has their own access to the system.
  • It allocates access rights to each account, so receptionists, dentists and managers each see only the folders and files their role needs.
  • It allows accounts to be grouped by role, so a new dentist can be given the same permissions as the existing dentists quickly instead of setting each one by hand.
  • It can require strong passwords, which makes it harder for one member of staff to log on using another person's account and open patient records.
  • It can disable or delete an account when a member of staff leaves, so that they can no longer open patient records.

Levels

  • Level 0 (0 marks): No rewardable content.
  • Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
  • Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
  • Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must cover both file management and user management and develop how each supports the practice, for example linking permissions to who can open patient records. Answers that only state basic, undeveloped points such as 'the operating system puts files in folders' or 'users have a username and password', with little reference to the practice, are limited to Level 1 (maximum 2 marks).

Do not accept backup, disk defragmentation or anti-malware software as operating system file management, or encryption, as these are outside the operating system's file management; they are utility software or security measures.

Example answers and how they were marked
Full marks6/6

The operating system's file management lets the practice keep each patient's records in folders, and it carries out the saving, moving and deleting of those files, so a dentist can add notes to the right record after an appointment. File management also sets permissions on the shared folders, so receptionists can be given read-only access to appointment details but cannot change clinical notes, while dentists have write access. This reduces the risk of confidential patient records being seen or changed by the wrong staff. User management supports this because the operating system gives every member of staff their own account with a username and password, so anything done to a record can be traced to the person who did it. Accounts can be grouped by role, so when the practice takes on a new dentist the account can be given the same rights as the other dentists quickly rather than setting each permission by hand. When a member of staff leaves, their account can be disabled so they can no longer open patient records. Together this means the practice can share records across reception, dentists and managers while each person only reaches what their role needs.

Why: Level 3: both file management (folders, saving, permissions, read-only access) and user management (accounts, grouping by role, disabling accounts) are covered and developed, with sustained reasoning linking them to the practice's shared records and staff access.

Some marks2/6

File management puts the patient records into folders so they can be found. User management gives each member of staff a username and password so they can log on to the computer.

Why: Level 1: two basic, independent points, one on each area, with little development and little application to how they support the practice, so it is capped by the Level 1 guidance at 2 marks.

Some marks1/6

File management is when the operating system backs up all the files every night. User management is when the computer has a username so it stops viruses.

Why: Level 1 (1 mark): backup is not accepted as operating system file management, but the basic point that a user account has a username is creditworthy; the claim that it stops viruses is not creditworthy.

7Discuss6 marksTranslators Swap Remove

A student is writing a program in a high-level language. The student runs the program after every small change to check that it works.

Discuss whether the student should use an interpreter or a compiler while writing and testing the program.

Your answer should include:

  • how each translator deals with a syntax error
  • how much of the program is translated at a time
  • how this affects the student's testing.
[6 marks]
Mark scheme

Indicative content

How each translator deals with a syntax error

  • An interpreter stops as soon as it finds a syntax error and displays an error message.
  • With an interpreter, the lines before the error have already been executed, so the student can see how far the program got before it stopped.
  • A compiler reports errors at the end of translation, so the student gets a list of all the syntax errors in the program in one go.

How much of the program is translated at a time

  • An interpreter translates one line at a time and executes each line immediately.
  • A compiler translates the whole program in one go before any of it is run.
  • A compiler produces object code, so after every change the whole program must be compiled again before the student can run it.
  • An interpreter produces no object code, so the student does not have to wait for the whole program to be translated before it runs.

How this affects the student's testing

  • An interpreter suits this student because the program can be run straight away after each small change.
  • The interpreter stops at the first error found, so the student fixes that error and runs the program again, but may only find the next error on the next run.
  • Reporting every error at the end of compilation means the student can fix several errors at once, but cannot run the program until the whole program compiles.
  • The student should use an interpreter while testing, and compile the finished program once it works.

Levels

  • Level 0 (0 marks): No rewardable content.
  • Level 1 (1–2 marks): Basic, independent points are made, showing elements of understanding of key concepts/principles of computer science. (AO1) The discussion will contain basic information with little linkage between points made or application to the context. (AO2)
  • Level 2 (3–4 marks): Demonstrates adequate understanding of key concepts/principles of computer science. (AO1) The discussion shows some linkages and lines of reasoning with some structure and application to the context. (AO2)
  • Level 3 (5–6 marks): Demonstrates comprehensive understanding of key concepts/principles of computer science to support the discussion being presented. (AO1) The discussion is well developed, with sustained lines of reasoning that are coherent and logically structured, and which clearly apply to the context. (AO2)

Level 3 responses must relate the way each translator works to the student's testing, not just describe the two translators.

Do not accept answers about run-time or logic errors where no comparison of the translators is made.

Example answers and how they were marked
Full marks6/6

The student should use an interpreter while testing. An interpreter translates one line at a time and executes each line straight away, so as soon as the student has made a small change the program can be run without waiting for the whole program to be translated. If there is a syntax error, the interpreter stops at that line and displays an error message, and the lines before it have already been executed, so the student knows exactly where the problem is. A compiler translates the whole program in one go and only reports the errors at the end, so the student would get a list of all the syntax errors, but could not run any of the program until the whole program compiled successfully.

Why: Explains how each translator deals with a syntax error, how much is translated at a time (one line executed immediately against the whole program at once) and links both to the student's testing, with a conclusion. Level 3.

Some marks4/6

An interpreter translates one line at a time and stops when it finds an error, so the student can see where the error is. A compiler translates the whole program and reports all the errors at the end. The interpreter is better for testing because the student can run the program straight away after a change.

Why: Adequate: correct points about error reporting and one line at a time, with a recommendation, but the effect on testing is only asserted rather than reasoned through, so the linkage is not sustained. Level 2.

Some marks1/6

The student should use a compiler because it translates the program one line at a time and stops at the first error, which makes testing quicker.

Why: The roles of the two translators are reversed, so the answer only makes a basic point about testing more quickly. Level 1.

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