A Level Computer Science (A2) chapter 4: System Software MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
67 exam-style questions on System Software, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. A program has a syntax error in a branch of code that is never executed on a test run. What happens with an interpreter?
A
the program will not start at all when it is run by the user
B
the error is reported before any statement has been run
C
the program may run to completion without the error being noticed
D
the interpreter will correct the error by itself as it runs
Show answer
Answer: C. An interpreter checks each statement only when it reaches it, so a faulty statement that is never reached is not reported. A compiler would report the error while translating the whole program.
2. How does a round-robin scheduler share the processor?
A
the process with the shortest burst time always runs first and to the end
B
each process runs until it completes, in order of arrival
C
the process that arrived last is always the one that runs first
D
each process runs for a fixed time slice, then rejoins the ready queue
Show answer
Answer: D. In round robin, each process gets the same time slice and then the next ready process is given the processor, so no process waits too long.
3. What is the value of the RPN expression 12 3 / 2 -?
A
2
B
10
C
−2
D
5
Show answer
Answer: A. 12 3 / gives 4; 4 2 − gives 2. When an operator is met, the second value taken from the stack is the left operand, so 4 − 2 and not 2 − 4.
4. In a paging system, the page table records what?
A
the name of the user who owns each one of the pages in memory
B
the number of times each file has been opened
C
the frame of main memory in which each page is held
D
the total size of the disk that is in the computer
Show answer
Answer: C. The page table translates a page number into a memory frame number, and marks pages that are only on disk.
5. Which change of state can happen when a running process asks to read data from a disk?
A
running to ready
B
running to blocked
C
blocked to running
D
ready to blocked
Show answer
Answer: B. The process cannot continue until the disk transfer has completed, so it moves to the blocked state and the processor is given to another process.
6. Which is the Reverse Polish Notation of the expression (a + b) * c?
A
a b c + *
B
a + b * c
C
a b + c *
D
* + a b c
Show answer
Answer: C. a b + gives the sum, and this is then multiplied by c: a b + c *. The expression a b c + * would mean a * (b + c).
7. What is disk thrashing?
A
the processor spends most of its time swapping pages, not running programs
B
the hard disk is physically damaged by the heat inside the case
C
a disk is filled with files and has no more free space left
D
the disk is being scanned for viruses by the security software running
Show answer
Answer: A. When RAM is too small for the pages that processes need, page faults occur constantly. Each fault means a slow disk transfer, so little useful work is done.
8. Which shows the stages of compilation in the correct order?
Answer: C. The source is first broken into tokens (lexical analysis), then checked against the grammar (syntax analysis), then converted to object code, which is finally improved (optimisation).
9. An RPN expression is evaluated using a stack. What is done when an operator such as + is read?
A
the operator is pushed onto the top of the stack and kept there
B
the next value is read and added to the top value only
C
the top two values are popped, added, and the sum is pushed back
D
the stack is emptied and the operator is discarded
Show answer
Answer: C. A binary operator takes its two operands from the top of the stack; the result goes back on the stack for later operators to use.
10. Which is the main difference between paging and segmentation?
A
pages are fixed-size blocks, but segments vary in size
B
pages are variable-size blocks, but segments have a fixed size
C
segments are used only in secondary storage, never in RAM
D
paging is used only for ROM and never for RAM
Show answer
Answer: A. Paging divides memory into equal-sized pages without regard to the content of the program. Segmentation divides a program into logical units, such as code, data or a stack, of different sizes.
67, each with the answer and a short explanation, across 2 topics: Purposes of an Operating System (OS), Translation Software. Every chapter test draws ten of them, so you can take it many times.
Is the A Level Computer Science (A2) chapter 4 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
