GCE O Level Computer Science 2024Paper 1 · version 3

A web browser reads the HTML code of a page and displays it. Compilers and assemblers translate program code into machine code; they do not display web pages.

The range runs over 5 columns (A, B, C, D, E) and 5 rows (1 to 5), so it has 5 × 5 = 25 cells.

Convert to decimal to check: 10101₂ = 21 and 1111₂ = 15. 21 − 15 = 6, and 6 in 4-bit binary is 0110.

Iteration (a loop) repeats a block of instructions. Sequence runs steps one after another; selection chooses between paths.

A parity check adds an extra bit so the receiver can detect whether bits were changed during transmission. Format and length checks are for data entry, not transmission.

A repeater receives a weak signal, regenerates it and sends it on at full strength, so it can travel further.

A database management system (such as MS Access) is used to carry out a user task, storing and querying data, so it is application software, not system software.

A Trojan horse pretends to be useful, legitimate software while hiding harmful code. A virus attaches to files and a worm spreads by itself across networks.

Two cores at 1.1 GHz can do about 2.2 GHz of work in parallel, and 4 GB is the most RAM (the maximum a 32-bit system can use). Option D runs at only 500 Hz, which is extremely slow.

Bit < Byte (8 bits) < Kilobyte (1024 bytes) < Terabyte.

The computer in the control room acts as the server and the café computers are its clients: a client-server network. In peer-to-peer, all computers are equal.

A good algorithm must be precise and unambiguous, finish in finite time and follow a logical order. Being ambiguous is the opposite of what is needed.

In https://www.cgceboard.cm/homepage.html, 'https' is the protocol, 'www' is the host, 'cgceboard.cm' is the domain name and 'homepage.html' is the file (page).

A fax (facsimile) machine scans a document or image and sends it over a telephone line to another fax machine, which prints it.

The output is 1 only when the two inputs are different (0,1 and 1,0) and 0 when they are the same. That is the XOR (exclusive OR) gate.

The parallelogram is used for input and output. The rectangle is a process, the diamond is a decision and the rounded shape (oval) is start/stop.

ATM stands for Automated Teller Machine.

The date, time and BIOS settings are kept in CMOS memory, powered by a small battery. When the CMOS battery fails, the computer forgets the date and time.

If–Then–Else chooses between two paths depending on a condition, so it is selection (decision).

The OR gate's output goes into a NOT gate (the triangle with the small circle), which inverts it. NOT-OR is the NOR gate.

Netiquette (net + etiquette) is the set of rules for respectful behaviour online.

An expert system holds the knowledge of human experts in a knowledge base and uses rules to reason and give advice, like a doctor or engineer would.

The project manager plans the project, follows its schedule and budget, and makes sure it is delivered on time with acceptable quality.

Options A and B are advantages. Because the account is reached over a network, a real disadvantage is the risk of accounts being hacked.

Tracks are the concentric circles on the disk surface. Each track is divided into sectors.

Parallel running means the old and new systems are used at the same time until the new one is trusted. Direct changeover replaces the old system at once.

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The extension .avi is a video format. .jpeg is an image, and .wav and .mp3 are audio files.

A compiler translates the whole source code of a high-level program into machine code (object code) before it is run.

Digital computers work with discrete values (0s and 1s). Analog computers use continuous data, and hybrid computers use both.

1 picosecond = 10⁻¹² s, 1 nanosecond = 10⁻⁹ s and 1 millisecond = 10⁻³ s, so picoseconds < nanoseconds < milliseconds.

Android is an operating system for smartphones and tablets, made by Google.

Procedures are the rules and instructions that say how the people, hardware and software of an information system carry out each operation.

01100100 = 100 in decimal. Letters are coded in order, and 'a' is 3 places before 'd', so 100 − 3 = 97 = 01100001.

A web address is a URL: Uniform Resource Locator.

Each student is one record (one row), so 150 students give 150 records. The 5 headings are the fields (columns).

CRT (cathode ray tube) monitors fire electron beams at the screen and give off more radiation than flat LCD screens.

Changing input values to see how the results change is what-if analysis, often done in a spreadsheet.

A dual-core processor has two processing units on one chip, so it can process about twice as much data as a single core. It does not double the motherboard, system unit or memory.

A dry run means going through the algorithm by hand with test values (often using a trace table) to check that it gives the right result.

Convert each hex digit to 4 bits: C = 12 = 1100 and D = 13 = 1101, so CD₁₆ = 11001101₂.

Slack (float) time is the time a task can be delayed without delaying the whole project. Tasks on the critical path have zero slack.

The system reads the temperature and acts on it automatically (switching off at 80 °C, on below 50 °C). Acting on the readings makes it a control system; a monitoring system only records them.

Twisted-pair, coaxial and fibre-optic are cables (guided media). Microwaves travel through the air, so they are wireless (unguided) media.

A Gantt chart shows each task as a bar against time, from the start to the end of a project.

A Boolean holds only TRUE or FALSE (1 or 0).

Comments are notes for programmers. The compiler ignores them, so they are never compiled into the program.

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A graphical user interface (GUI) lets the user click on icons, menus and buttons. A command line interface needs typed commands.

A demultiplexer takes one combined channel and splits it back into several. A multiplexer does the opposite: it combines several signals into one channel.