Download AQA A-LEVEL COMPUTER SCIENCE: HARDWARE & SOFTWARE and more Exams Health sciences in PDF only on Docsity!
AQA A-LEVEL COMPUTER SCIENCE: HARDWARE &
SOFTWARE 2026 EXAM WITH QUESTIONS AND
CORRECT VERIFIED ANSWERS (100% CORRECT
ANSWERS) | AQA A-LEVEL COMPUTER SCIENCE
HARDWARE & SOFTWARE (100% SUCCESS
GUARANTEED)
Define hardware (2 marks) The electrical or electro-mechanical parts of a computer (1) on which software executes (1) Define software (2 marks) Sequences of instructions called programs (1) which are understood and able to be executed by hardware (1) State the two types of software System software and application software Define system software (2 marks) A layer of software which enables the user to operate the computer (1) and abstract the user from how the computer works (1) State the main use of system software To enable the user to operate the computer State the 4 types of system software
Operating system Utility programs Libraries Programming language translators Define utility software and give an example (2 marks) Software that performs a non-core/specific management function for a computer Examples include: backing up files, restoring corrupted files, de/compressing data, encrypting data, etc State 3 examples of utility software Disk defragmentation File backup File encryption Antivirus Describe how a disk defragmenter works as a part of utility software (3 marks) It reorganizes a hard disk so that files which have been split up into blocks (1) and stored all over the disks are recombined into single series of sequential blocks (1). This makes reading file quicker (1), optimizing the system and therefore being a part utility software. Define library software (3 marks)
State 2 ways in which software is bought Off-the-shelf Specially written by a team of programmers for a particular organisation State an example of bespoke software A hotel wants to buy some visitor booking software. They pay a group of developers to make a bespoke software that satisfies their requirements. Give an advantage and a disadvantage of using an off-the-shelf program rather than a bespoke program Advantage: It is ready to be installed immediately, more likely to be well- documented, more likely to be well-tested, more likely to be bug-free Disadvantages: Contains features which may never be used, wasting memory Describe 3 roles of the operating system Any 3 from the image Define operating system (3 marks) A set of programs (1) that manage the operations of the computer (1) for the user (1). State where the operating system is held on
Secondary storage Define loader (1 mark) The program that sends instruction to load the operating system when the computer starts up State where the loader is held in ROM Draw a diagram of how the user, software, the operating system and hardware interact State how an operating system disguises the complexities of interacting with hardware Via an API (Application Programming Interface) Describe how an API works (2 marks) An API produces an interface (1) through which users can complete tasks oblivious to the actual operations taking place (1) State 5 functions of an operating system Providing abstraction from hardware Providing a user interface Memory management for processes Processor Scheduling Backing store management Management of input and output (I/O) devices
By carrying out small parts of multiple larger tasks (1) the processor gives the appearance of carrying out serveral tasks simultaneously (1) Define scheduler (1 mark) The operating system module responsible for ensuring that processor time is used as efficiently as possible State the 4 objectives of the scheduler Maximizing throughput Be fair to all users on a multi-user system Provide acceptable response time to all users Ensure hardware srouces are kept as busy as possible Define throughput (2 marks) How much information a system can process in a given time OR the number of processes that complete their execution time per unit time Define backing store management (1 mark) Using a directory kept on the operating system of where files are stored so that they can be quickly accessed Define peripheral management (2 marks) Managing the interactions between peripheral devices and applications (1) without causing conflicts (1) Define interrupt handling (3 marks)
Detecting the interrupt signal (1) and displaying an appropriate error message for the user (1) if needed (1) Define accumulator (1 mark) A register where results of calculations are stored Describe what an instruction looks like in machine code (2 marks) An instructions holds an operation code (opcode) in the first few bits (1) and an operand in the rest of the memory cell (1). Define operand (1 mark) The data to be operated on OR the address where the data is held Imagine that the instruction 0001 means: load the value stored in memory location specified by operand into the accumulator Write a line of machine code to load the value stored in memory location 8 into the accumulator (1 mark). 0001 1000 In Python, swapping two values in memory can be done with one line of code. State what this is an example of. Abstraction, as the user's doesnt know all the details of how the computer actually achieves the swap. Define low-level programming language (2 marks)
Define high-level language (4 marks) A programming language that enables programmers to think and code in terms of algorithms (1), without worrying about how each tiny step will be executed in machine code (1) and where each item of data will be stored (1). Each instruction in a high level language is translated into several low-leve language instructions (1). State 3 advantages of high-level languages over low-level languages
- They are relatively easy to learn
- It is much easier and faster to write a program with them
- Programs written in high-level languages are much easier to understand, debug and maintain
- Programs written in a high-level language are usually independent on the architecture of the machine they are running on
- There are many built-in library functions available in most high-level languages
- Some high-level languages are written specifically for a particular class of problem (e.g. SQL) State 3 examples of things that use assembly language Embedded systems Real-time systems Sensors Mobile phones Device drivers Interrupt handlers Describe 3 advantages of assembly code over high-level languages (6 marks)
Define instruction set (1 mark) The set of machine code instructions that a particular computer can execute State the program used to translate assembly code into machine code Assembler A computer cannot understand the assembly code "ADD A5". Explain how computers run assembly code (3 marks) The assembly code is translated into the equivalent machine code (1) using a program called an assembler (1). The assembler takes each assembly instruction and converts it to the 0's and 1's of the corresponding machine code instruction (1). An assembly program is translated using assembler. The result is stored in secondary storage for later use. State what program is needed for this to happen. A loader State what input to the assembler is called Source code Define object code (3 marks) Machine code (1) or Intermediate code (1) (e.g. bytecode) usually produced by a compiler (1) Describe how a compiler translates high-level code (4 marks)
Note: interpreters do not generate a translated program, and neither do they store one for later use Define bytecode (4 marks) An intermediate language between machine code and high-level language source code (1) produced by a compiler (1) for execution on a virtual machine (1) that is machine-independent (1) State how bytecode is executed Using a compiler Explain two advantages of bytecode (4 marks) You can achieve platform independence (1) as the bytecode interpreter masks differences between computer architectures and operating systems (1). It acts as an extra security layer (1) as you can download an untrusted program and execute the bytecode executor rather than the program itself (1) State whether assembler is portable or not It is not portable State whether interpeters are portable They are portable State whether compilers are portable
It depends:
- If the compiler generates machine code directly it is not portable
- If the compiler generates intermediate code like bytecode it is portable Explain how bytecode is used after it has been generated (2 marks) Any two of:
- Software must be used to finish the translation process (on the computer running the program)
- The intermediate language code / bytecode is compiled into machine code for the processor / platform / computer it is being executed on
- Using a virtual machine // a just-in-time / JIT compiler
- (The virtual machine will) interpret / translate / execute the intermediate language code / bytecode // call functions within its own code to carry out the command
- Each processor instruction set / architecture will have its own virtual machine; State 3 advantages of a compiler over an interpreter
- The object code can be saved on disk and run whenever required
- The end user only needs the executable code, instead of the source program and an interpreter
- Object code executes faster than interpreted code
- Object code can be distributed or executed without the compiler that was used to translate it
- Object code is more secure as it cannot be read without a great deal of reverse engineering. This allows the developer to charge for their work.
- There are no syntax or semantic errors
- It can be translated on one type of computer and run on another, UNLIKE interpreters
Any logic circuit can be made from only ... or .... gates. Fill in the blanks (2 marks) Any logic circuit can be made from only NAND or NOR gates State an advantage of using only NAND or NOR gates to construct logic circuits It makes producing circuits easier as only one type of gate is needed State how a logic gate can be represented data-wise On a truth table showing the output given for each possible input State what sort of letters are used for logic gate input A, B, C State what sort of letters are used for logic gate outpu P or Q Draw the logic gate symbol for the NOT gate Draw the truth table for the NOT logic gate State the boolean algebraic expression for the NOT logic gate. Assume the input is A and the output is Q. Q = Ā Draw the logic gate symbol for the AND gate Draw the truth table for the AND logic gate
State the boolean algebraic expression for the AND logic gate. Assume the inputs are A and B and that the output is Q. Q = A · B Draw the logic gate symbol for the OR gate Draw the truth table for the OR logic gate State the boolean algebraic expression for the OR logic gate. Assume the inputs are A and B and that the output is Q. Q = A + B Draw the logic gate symbol for the XOR gate Draw the truth table for the XOR logic gate State the boolean algebraic expression for the XOR logic gate. Assume the inputs are A and B and that the output is Q. Q = A ⊕ B Draw the logic gate symbol for the NAND gate Draw the truth table for the NAND logic gate State the boolean algebraic expression for the NAND logic gate. Assume the inputs are A and B and that the output is Q. Draw the logic gate symbol for the NOR logic gate. Draw the truth table for the NOR logic gate
State the 2nd associative rule X OR (Y OR Z) = (X OR Y) OR Z Alternatively, X OR (Y OR Z) = (X OR Z) OR Y State the first distributive rule X AND (Y OR Z) = X AND Y OR X AND Z State the second distributive rule (X OR Y) AND (W OR Z) = X AND W OR X AND Z OR Y AND W OR Y AND Z State the 1st absorption rule X OR (X AND Y) = X State the 2nd absorption rule X AND (X OR Y) = X Q = NOT(NOT(X AND (NOT Y)) AND ((NOT Y) OR Z)) Simplify this expression (6 marks) Q = NOT(NOT(X AND (NOT Y)) AND ((NOT Y) OR Z)) = X AND (NOT Y) AND ((NOT Y) OR Z) (1) = X AND (NOT Y) AND (NOT Y) OR X AND (NOT Y) AND Z (1) = X AND (NOT Y) OR X AND (NOT Y) AND Z (1) = X AND (NOT Y) AND (1 OR Z) (1)
= X AND (NOT Y) AND 1 (1)
= X AND (NOT Y) (1)
Q = A AND B OR NOT(A) OR NOT(B)
Simplify this expression (2 marks) Using de morgan's first law, Q = A AND B OR NOT(A) OR NOT(B) = A AND B OR NOT(A AND B) X OR NOT(X) is always 1, since there will always be at least one 1. Therefore A AND B OR NOT(A AND B) = 1 1 mark for each step For 6 marks, show that (A OR B) AND (A OR C) = A OR B AND C According to 2nd distributive rule, (A OR B) AND (A OR C) = (A AND A) OR (A AND C) OR (B AND A) OR (B AND C) A AND A = A Therefore (A AND A) OR (A AND C) OR (B AND A) OR (B AND C) = A OR (A AND C) OR (A AND B) OR (B AND C) According to commutative rules, A OR (A AND C) OR (A AND B) OR (B AND C) = A OR (A AND B) OR (A AND C) OR (B AND C)
