Computer Science 9618/12 May/June 2023: question paper and mark scheme

Mark scheme

1(a) 1 mark each to max 2 2 Allows the sharing of files/data // Allows communication between the devices Allows the sharing of resources e.g. hardware / software (applications) Allows central management // by example, backup, security, etc. 1(b) 1 mark each to max 2 2 Covers a small geographical area The infrastructure is privately owned // not controlled by external organisations 1(c) 1 mark each to max 2 2 Each computer directly connected only to the server ... ... all components correctly labelled Computer Computer 4 1 Server Computer Computer 1(d) 1 mark each to max 3 3 A protocol (suite) For data transmission over standard / universal wired / cabled network connections Uses Carrier Sense Multiple Access / Collision Detection (CSMA/CD) Data is transmitted in frames … each frame has a source and destination (IP/MAC) address ... and error checking data (so damaged frames can be resent) 1(e) 1 mark each 2 The server performs minimal / some processing for the client The clients also do most of their own processing/work independently // most of the resources are installed locally

Mark scheme

2(a) 1 mark for each correct feature or description 4 Feature Description Data dictionary Data about the data in the database // data about the structure of the database // metadata for a database Query processor Software that allows the user to enter criteria, then finds and returns the appropriate result // software that processes and executes queries written in SQL Logical schema A model of a database that is not specific to one DBMS Developer interface A software tool that allows the user to create items such as tables, forms and reports 2(b) 1 mark each to max 3 3 Referential Integrity makes sure data is consistent Referential Integrity makes sure all data is up-to-date Referential integrity ensures that every foreign key has a corresponding primary key Referential Integrity prevents records from being added / deleted / modified incorrectly Referential Integrity makes sure that if data is changed in one place the change is reflected in all related records Referential Integrity makes sure any queries return accurate and complete results 2(c)(i) 1 mark each to max 2 2 Presence check to make sure that the (rider level) is entered Look-up / Existence check to make sure the rider level is only Beginner, Intermediate or Advanced Length check to make sure the rider level entered is either 8 or 12 characters Type check to make sure the rider level is alphanumeric 2(c)(ii) 1 mark each 4 SELECT field Name FROM table HORSE WHERE with Intermediate / Beginner OR with Beginner / Intermediate Example answer: SELECT Name FROM HORSE WHERE HorseLevel = "Intermediate" OR HorseLevel = "Beginner"; 2(c)(iii) 1 mark each 4 SUM should be COUNT // SELECT COUNT(STUDENT.RiderLevel) The WHERE statement needs the table names before each field name // WHERE STUDENT.StudentID = LESSON.StudentID The OR should be AND // AND Date = #09/09/2023# Beginner is missing the speech marks // STUDENT.RiderLevel = "Beginner";

Mark scheme

3(a) 1 mark for generates object code to second pass 3 1 mark for reads source code one line at a time to both boxes 1 mark for removes white space and adds labels to first pass Action Pass generates object code first reads the source code one line at a time removes white space second adds labels to the symbol table 3(b) 1 mark for each correct term 3 Direct addressing is when the operand holds the memory address of the data. Indirect addressing is when the operand holds a memory address that stores the memory address of the data. Immediate addressing is when the operand is the data.

Mark scheme

4(a) 216 // 65536 1 4(b) 1 mark for working; 1 mark for answer 2 Working: +120 = 0111 1000 Answer: 1000 0111 4(c) 1 mark for working; 1 mark for answer 2 Working: A04 = (10 * 162) + 4 // A04 = (10 * 256) + 4 // A04 = 1010 0000 0100 Answer: 2564 4(d) 0011 1100 1

Mark scheme

5(a) 1 mark each to max 2 2 Examples: Interrupt Timing Read Write 5(b) 1 mark for description; 1 mark for corresponding explanation 4 Examples Increase number of cores Each core can independently carry out a process at the same time // so that more instructions are performed in parallel Increase RAM capacity ... allowing more applications to reside in memory at the same time, saving disk access times Increase cache memory More data can be stored in fast access so less time is spent accessing from RAM Increase clock speed More Fetch-Decode-Execute (FDE) cycles can run each second / per unit time 5(c)(i) 1 mark for a correct answer 1 1 bit is transferred at a time Can be synchronous or asynchronous USB-3 is full duplex and earlier versions are half-duplex 5(c)(ii) 1 mark for identification of a suitable port 1 Examples HDMI DisplayPort 5(d)(i) 1 mark each to max 5 5 Manages the scheduling of processes // decides which order to run processes Manages which resources the processes require … such as allocating memory Enables processes to share data Prevents interference between processes // resolution of conflicts Handles the process queue It allows multi-tasking / multi-processing ... by ensuring fair access, handling priorities and handling interrupts 5(d)(ii) 1 mark each to max 2 2 To help users to set-up / configure / analyse / optimise / maintain the computer ... ... by for example, making memory allocation more efficient ... by for example, checking the system for faults

Mark scheme

6(a) 1 mark for correct XOR and AND gates, with correct inputs 2 1 mark for correct NOT and NOR gates with correct inputs 6(b) 1 mark for first 4 rows 2 1 mark for last 4 rows P Q R Working space Z 0 0 0 0 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 0 1 1 0 1 1 1 1 1

Mark scheme

7(a)(i) 1 mark each to max 2 2 Set of pre-written / pre-compiled / pre-tested subroutines ... which can be called in other programs ... by installing/importing the library 7(a)(ii) 1 mark for each bullet point. Mark in pairs; 1 mark for a benefit and 1 mark for 4 an appropriate expansion (main) memory requirements for program is reduced ... as dynamic link library is loaded only once / when required the executable file size of the program using the DLL will be smaller ... because the executable does not contain (all) the library routines maintenance not needed to be done by the programmer ... because the DLL is separate from program no need to recompile the main program when changes are made to DLL ... because changes / improvements/ error correction to the DLL file code are done independently of the main program A single DLL file can be made available to several application programs ... Saving space in memory / easing the pressure on memory 7(b) No mark for choice. 1 mark each to max 3 for justification 3 Interpreter Allows the developer to make real-time changes … so the program can be debugged at each stage ... the effect of any changes made by the developer can be seen immediately The developer can test when incomplete … so small parts can be tested without having to test the rest of the program … if one section does not work others can still be tested To avoid dependent errors Compiler The developer can debug multiple errors simultaneously Produces an executable file … so that the developer can test the program multiple times without recompiling 7(c) 1 mark each 4 Breakpoints: Stop the code at a specific line to check the current progress / values Dynamic syntax checks: Highlight / underline / colour syntax errors as the code is entered Context-sensitive prompts: Suggest the code to add // automatically complete statements Single stepping: Run the code one line at a time so the values can be checked 7(d) 1 mark each to max 3 3 Uses speech recognition ... which identifies key phrases / words spoken … and matches these to a database ... and generates the most likely sentence / command / word