AQA_2024: AS Computer Science - Paper 1 (Merged Question Paper and Marking Scheme)

AQA_2024: AS Computer Science - Paper 1 (Merged Question Paper and Marking Scheme) AS COMPUTER SCIENCE Paper 1 Tuesday 14 May 2024 Materials For this paper you must have:  a computer  a printer  appropriate software  the Electronic Answer Document Afternoon Time allowed: 1 hour 45 minutes  an electronic version and a hard copy of the Skeleton Program  an electronic version and a hard copy of the Preliminary Material  an electronic version of the Data File SimulationD You must not use a calculator. Instructions  Type the information required on the front of your Electronic Answer Document.  Before the start of the examination make sure your Centre Number, Candidate Name and Candidate Number are shown clearly in the footer of every page (not the front cover) of your Electronic Answer Document.  Enter your answers into the Electronic Answer Document.  Answer all questions.  Save your work at regular intervals. Information  The marks for questions are shown in brackets.  The maximum mark for this paper is 75.  No extra time is allowed for printing and collating.  The question paper is divided into three sections. Advice You are advised to allocate time to each section as follows: Section A – 20 minutes; Section B – 25 minutes; Section C – 60 minutes. At the end of the examination Tie together all your printed Electronic Answer Document pages and hand them to the Invigilator. Warning It may not be possible to issue a result for this paper if your details are not on every page of your Electronic Answer Document. For AS Computer Science Paper 1, focus on the following key areas: 1. Problem Solving and Programming:  Programming Concepts: Be familiar with basic programming concepts like variables, data types, constants, operators, and control structures (if-else, loops, case statements).  Algorithms: Understand common algorithms such as searching algorithms (linear search, binary search), sorting algorithms (bubble sort, quicksort), and their time complexities (Big O notation). 2. Data Representation:  Binary and Hexadecimal: Know how to convert between binary, hexadecimal, and decimal. Understand how to perform binary arithmetic (addition, subtraction).  Data Storage: Understand how data is represented and stored in a computer, including ASCII, Unicode, and image representation using pixels and colour depth. 3. Computational Logic:  Boolean Algebra: Understand Boolean operations such as AND, OR, NOT, and how to simplify Boolean expressions using laws and Karnaugh maps.  Logic Gates: Be familiar with basic logic gates (AND, OR, NOT, NAND, NOR, XOR) and their truth tables.  Truth Tables: Know how to construct and interpret truth tables for simple Boolean expressions and logic circuits. 4. Computer Systems:  Hardware Components: Understand the basic components of a computer system (CPU, RAM, input/output devices, storage devices). Know the role of the Control Unit, ALU, and Registers in the CPU.  Von Neumann Architecture: Be familiar with the Von Neumann architecture, including the fetch-decode execute cycle and how it relates to machine instructions. 5. Networking and Communication:  Network Topologies: Understand different network topologies, such as star, ring, bus, and their advantages and disadvantages.  Protocols: Be familiar with key networking protocols like TCP/IP, HTTP, FTP, and DNS. Understand their roles in communication over networks.  OSI Model: Know the OSI model and the seven layers, understanding the function of each layer in network communication.  IP Addressing: Understand the concept of IP addresses, including IPv4 and IPv6, and how subnetting works. 6. Software Development:  Development Methodologies: Understand different software development methodologies, such as Waterfall, Agile, and Iterative development.  Testing and Debugging: Be familiar with the concepts of unit testing, integration testing, and debugging techniques used to identify and resolve issues in code.  Version Control: Know how version control systems like Git work, and understand the importance of branches, commits, and merging in collaborative coding projec IB/M/Jun24/G4001/E7 7516/1 2 Section A You are advised to spend no more than 20 minutes on this section. Enter your answers to Section A in your Electronic Answer Document. You must save this document at regular intervals. Question 04 in this section asks you to write program code starting from a new program/project/file. You are advised to save your program at regular intervals. 0 1 Figure 1 S1  "011101" S2  "001100" C  "0" R  "" FOR J = 0 TO 5 X  5 - J D1  S1[X] D2  S2[X] IF C = "0" THEN IF D1 = D2 THEN S  "0" C  D1 ELSE S  "1" ENDIF ELSE IF D1 = D2 THEN S  "1" C  D1 ELSE S  "0" ENDIF ENDIF R  CONCATENATE(S, R) ENDFOR OUTPUT R The function CONCATENATE(X, Y) returns the string formed by concatenating the string Y to the end of string X. For example, CONCATENATE("cat", "dog") returns "catdog". The strings are zero index based. IB/M/Jun24/7516/1 3 Complete Table 1 by hand-tracing the algorithm in Figure 1. You may not need to use all the rows in Table 1. You do not need to indicate that C, D1, D2 and S are strings. The first row of Table 1 has already been completed for you. Table 1 S1 S2 C R J X D1 D2 S "011101" "001100" "0" "" OUTPUT: Copy the contents of all the unshaded cells in Table 1 into your Electronic Answer Document. [5 marks] Turn over ► IB/M/Jun24/7516/1 4 0 2 A program uses both local and global variables. 0 2 . 1 State two differences between local and global variables. 0 2 . 2 Give two reasons why it is good practice to use local variables. [2 marks] [2 marks] 0 3 Programmers are encouraged to adopt a structured approach to writing programs. Explain three reasons for adopting the structured approach. 0 4 Figure 2 shows an algorithm represented using pseudo-code. Figure 2 OUT_NOLF "Enter an integer: " INPUT Number1 OUT_NOLF "Enter another integer: " INPUT Number2 IF Number1 > Number2 THEN Number  Number1 DIV Number2 ELSE Number  Number2 DIV Number1 ENDIF Count  0 WHILE Count ≠ Number Count  Count + 1 IF (Count MOD 10) = 0 THEN OUT_NOLF "X" ELSE IF (Count MOD 5) = 0 THEN OUT_NOLF "V" ELSE OUT_NOLF "/" ENDIF ENDIF ENDWHILE [3 marks] The OUT_NOLF command displays the output without a line feed. The following series of OUT_NOLF commands will display ABC: OUT_NOLF "A" OUT_NOLF "B" OUT_NOLF "C" IB/M/Jun24/7516/1 5 Table 2 lists the MOD and DIV operators for each of the available programming languages. You should refer to the row for your programming language. Table 2 Programming language MOD C# DIV % Java / % Pascal / mod Python div % VB.NET // Mo