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A-LevelComputer ScienceProgramming Paradigms and Program StructureOct/Nov 2023Paper 2 Q819 Marks

8 A class of students are developing a program to send data between computers. Many computers are connected together to form a wired network. Serial ports are used to connect one computer to another. Each computer: • is assigned a unique three-digit ID • has three ports, each identified by an integer value • is connected to between one and three other computers. Messages are sent between computers as a string of characters organised into fields as shown: <STX><DestinationID><SourceID><Data><ETX> Field number Field name Description n/a STX a single character marking the start of the message (ASCII value 02) 1 DestinationID three numeric characters that identify the destination computer 2 SourceID three numeric characters that identify the source computer 3 Data a variable length string containing the data being sent (Minimum length is 1 character) n/a ETX a single character marking the end of the message (ASCII value 03) For example, the following message contains the data "Hello Kevin" being sent from computer "101" to computer "232": <STX>"232101Hello Kevin"<ETX> Each computer will run a copy of the same program. Each program will contain a global variable, MyID of type string, that contains the unique ID of the computer in which the program is running. The programmer has defined the first two program modules as follows: Module Description Transmit() (already written) • takes two parameters: ○ a string containing a message ○ an integer containing a port number • transmits the message using the given port SendFile() • takes three parameters: ○ a string containing a text file name ○ a string containing a Destination ID ○ an integer containing a Port number • transmits the file one line at a time • transmits a final message with data string "****"

📋 Examiner Report & Trap Analysis

Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...

🎯 Mark Scheme Breakdown

Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.

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About This A-Level Computer Science Question

Topic

This structured question tests Programming Paradigms and Program Structure in A-Level Computer Science (syllabus code 9618). It is worth 19 marks.

Source

This question appeared in the Cambridge A-Level Computer Science Oct/Nov 2023 examination, Paper 2 Variant 1.

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