AS Level Computer Science MCQs with answers
Practise AS Level Computer Science (9618) with 336 exam-style MCQs, each with the answer and a short explanation. Every test is marked the moment you finish and shows your score chapter by chapter, so you know what to revise next. It is free and needs no sign-up.
336 questions · 12 chapters
What each chapter covers 12 chapters
The questions follow the syllabus chapter by chapter. You can test the whole subject or one chapter at a time.
- Information representation 33 questionsData representation, Multimedia, Compression
- Communication 28 questionsNetworks and network models, Network hardware and the internet
- Hardware 25 questionsComputers and their components, Logic gates and logic circuits
- Processor fundamentals 33 questionsCentral Processing Unit (CPU) architecture, Assembly language, Bit manipulation
- System software 20 questionsOperating systems, Language translators
- Security, privacy and data integrity 23 questionsData security, Data integrity
- Ethics and ownership 12 questions
- Databases 36 questionsDatabase concepts, Database Management Systems (DBMS), Data Definition Language (DDL) and Data Manipulation Language (DML)
- Algorithm design and problem-solving 22 questionsComputational thinking skills, Algorithms
- Data types and structures 40 questionsData types and records, Arrays, Files, Introduction to Abstract Data Types (ADT)
- Programming 32 questionsProgramming basics, Constructs, Structured programming
- Software development 32 questionsProgram development life cycle, Program design, Program testing and maintenance
Sample AS Level Computer Science MCQs with answers 12 questions
12 questions from the test, one or two from each chapter. Try each one, then open the answer.
1. What is the hexadecimal number 3F in denary?
- A
62
- B
63
- C
315
- D
48
Show answer
Answer: B. 3 × 16 + 15 = 63 (F = 15). 315 comes from writing the digit values side by side instead of using place value.
2. What does a modem do when a computer connects to the internet over a PSTN telephone line?
- A
assigns IP addresses to each device on the LAN
- B
stores copies of web pages locally to speed up access
- C
converts digital data to analogue signals and back
- D
translates the URLs typed by users into IP addresses
Show answer
Answer: C. The telephone line carries analogue signals, so the modem modulates the computer's digital data and demodulates incoming signals.
3. How does EEPROM differ from EPROM?
- A
EEPROM can be written only once; EPROM can be rewritten
- B
EEPROM is erased electrically in place; EPROM by UV light
- C
EEPROM is volatile, but EPROM keeps its data without power
- D
EEPROM is erased using UV light, but EPROM electrically
Show answer
Answer: B. EPROM is erased by shining ultraviolet light through a window, usually after removing the chip. EEPROM is erased and rewritten electrically while in the circuit.
4. One byte in memory controls eight lights, one bit per light. Why is bit manipulation useful here?
- A
it lets all eight lights share one bit
- B
it converts the byte to BCD for display
- C
one light can be switched without affecting the others
- D
it doubles the number of lights that can be controlled
Show answer
Answer: C. With a mask, a single bit can be set, cleared or tested while the other seven bits, and so the other lights, stay unchanged.
5. What is a benefit of Java's approach of compiling to bytecode?
- A
the program never needs to be translated into machine code
- B
it always runs faster than a fully compiled program would
- C
the bytecode runs on any computer that has a virtual machine
- D
syntax errors are only found when the program is run
Show answer
Answer: C. Bytecode is platform-independent: each type of computer has its own virtual machine, so one compiled file runs on all of them.
6. Why can a single parity bit per byte not detect every transmission error?
- A
if two bits flip, the byte still has the correct parity
- B
the parity bit itself is sometimes lost during transfer
- C
parity only works when an odd number of bytes is sent
- D
parity checks the order of bytes, not their values
Show answer
Answer: A. Changing two bits keeps the count of 1s odd or even as before, so the error goes unnoticed. A parity block check or checksum gives better protection.
7. A program can be used free for 30 days, after which the user must pay to keep using it. Which type of licence is this?
- A
open source
- B
free software
- C
shareware
- D
commercial
Show answer
Answer: C. Shareware lets people try the software, often with limited features or time, before paying. Commercial software must be paid for before use.
8. Which statement increases by 2 the price of every book whose author is Smith?
- A
UPDATE BOOK SET Price = Price + 2 WHERE Author = 'Smith';
- B
UPDATE BOOK SET Price = Price + 2;
- C
INSERT INTO BOOK (Price) VALUES (Price + 2) WHERE Author = 'Smith';
- D
ALTER TABLE BOOK SET Price = Price + 2 WHERE Author = 'Smith';
Show answer
Answer: A. UPDATE ... SET ... WHERE changes existing records that match the condition. Without WHERE, every book's price would rise.
9. A program models a bus route to plan timetables. Which detail should be left out of the abstract model?
- A
the distance between each pair of stops
- B
the average time for passengers to board
- C
the number of buses that are available
- D
the colour of the seats fitted in each bus
Show answer
Answer: D. Seat colour has no effect on journey times, so it is not an essential detail. Distances, boarding times and bus numbers all affect the timetable.
10. Stock is an array of 3 records. Stock[1] has Price 2.0 and Qty 4; Stock[2] has Price 3.5 and Qty 2; Stock[3] has Price 1.0 and Qty 10. What is Value after this code?
Value ← 0
FOR i ← 1 TO 3
Value ← Value + Stock[i].Price * Stock[i].Qty
NEXT i
- A
6.5
- B
16
- C
15
- D
25
Show answer
Answer: D. i = 1: 2.0 × 4 = 8. i = 2: 3.5 × 2 = 7, total 15. i = 3: 1.0 × 10 = 10, total 25. Stopping at 15 misses the last record.
11. What is meant by the interface of a procedure?
- A
the statements between PROCEDURE and ENDPROCEDURE
- B
the list of local variables declared inside it
- C
the value that the procedure returns to its caller
- D
its parameters, their types and how each is passed
Show answer
Answer: D. The interface is how the module communicates with the rest of the program: its name, parameters, their types and whether they are BYVAL or BYREF.
12. On a structure chart, a small arrow beside a connecting line has a hollow (empty) circle at its tail. What does it show?
- A
a Boolean flag passed between modules
- B
a data parameter passed between modules
- C
a module that is called repeatedly
- D
a choice of which module is called
Show answer
Answer: B. An arrow with an empty circle is a data couple (a parameter). A filled circle marks a flag, a Boolean value such as Found.
Try 324 more questions
Ways to practise 5 ways
- Quick check. 10 questions drawn fresh each time, about 10 minutes.
- By chapter. 10 questions from one chapter, for the topic you are revising now.
- Full paper. A full-length timed paper across the whole syllabus.
- Practice mode. See the right answer and an explanation after every question, with no clock.
- Exam mode. Timed like the real paper, with no going back.
Common questions
Is this AS Level Computer Science test free?
Yes. Every test and every explanation is free, and you do not need an account. If you sign in, your results are kept across your devices.
Are these past paper questions?
The 336 MCQs are our own, written to the syllabus in the style of the exam.
How is the test marked?
Instantly. You get your score, the right answer and an explanation for every question, and a list of the topics to work on.
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