AS & A Level Computer Science (9618) Paper 1 Practice Flashcards

Comprehensive question-and-answer revision flashcards covering all major topics of the Cambridge AS Level Computer Science (9618) Paper 1 syllabus.

What is the key difference between binary prefixes and denary prefixes?

Binary prefixes (KiB, MiB, GiB, TiB) are based on powers of 2 ($2^{10}$, $2^{20}$, $2^{30}$, $2^{40}$), whereas denary prefixes (KB, MB, GB, TB) are based on powers of 10 ($10^3$, $10^6$, $10^9$, $10^{12}$).

What is Binary Coded Decimal (BCD) and what are its primary benefits?

BCD represents each non-negative denary digit using a 4-bit binary sequence (a nibble). Its benefits include straightforward conversion between BCD and denary, easier display on digital equipment, and accurate representation of monetary values.

What is the formula for calculating the file size of a bitmap image in bytes?

$$\text{File Size in Bytes} = \frac{\text{Width} \times \text{Height} \times \text{Bit Depth}}{8}$$

What are the main differences between ASCII and Unicode character sets?

ASCII uses $7$ bits per character ($128$ characters), represents English only, is non-standardised, and uses less storage space. Unicode uses $16$ or $32$ bits per character ($65536$+ characters), supports multiple languages and emojis, is standardised, and uses more storage space.

What is the difference between lossy and lossless file compression?

Lossy compression permanently removes data to reduce file size, making it irreversible and causing quality loss. Lossless compression encodes data to reduce size without losing any data, making it completely reversible.

What is an embedded system and what are its key features?

An embedded system is a microprocessor dedicated to one specific task. Key features include being built into a larger system, containing non-easily updated firmware, having no general-purpose OS or extra peripherals, and requiring a processor, memory, and I/O capability.

How does a Solid State Drive (SSD) store data using flash memory?

SSDs store data in NAND flash memory using memory cells with floating gate and control gate transistors. Floating gates trap or free electrons to represent binary $1$ or $0$, controlled during read, write, and erase operations.

What is the main difference between RAM and ROM?

RAM is volatile, temporary memory that allows read/write operations and stores currently running data and instructions. ROM is non-volatile, permanent memory that allows read-only operations and stores boot-up instructions.

What are the key differences between Static RAM (SRAM) and Dynamic RAM (DRAM)?

DRAM uses a single transistor and capacitor per bit, requires continuous refreshing, has higher density, is slower, and is used for main memory. SRAM uses flip-flops/latches with multiple transistors, needs no refreshing, is faster, and is used for CPU cache memory.

What is the difference between a monitoring system and a control system?

A monitoring system only measures and reports status without taking action or using feedback or actuators. A control system uses feedback and actuators to perform automatic actions to maintain target system conditions.

What is the Von-Neumann Architecture's stored program concept?

It is the architecture concept where program instructions and data are stored together in the same memory space and are treated as indistinguishable by the system.

What are the roles of the Program Counter (PC) and Current Instruction Register (CIR)?

The PC stores the memory address of the next instruction to be fetched and increments automatically. The CIR stores the current instruction fetched from the MDR while it is decoded and executed by the CU.

How does the CPU handle interrupts during the Fetch-Execute cycle?

At the end of each FE cycle, the CPU checks interrupt flags. If a higher-priority interrupt exists, current register values are saved to a stack, the Interrupt Service Routine (ISR) runs, and then register values are restored from the stack.

What occurs during the First Pass and Second Pass of a Two-Pass Assembler?

First Pass removes comments/whitespace, parses labels, builds a symbol table, and assigns memory addresses. Second Pass replaces labels with absolute memory addresses using the symbol table and generates binary object code.

What is the difference between Phishing and Pharming?

Phishing uses fraudulent emails or messages to trick users into clicking links and inputting credentials. Pharming uses malicious code to corrupt DNS resolution or browser settings, automatically redirecting users to fake websites.

What is the difference between Data Validation and Data Verification?

Validation checks whether input data is reasonable, complete, and follows specified rules. Verification checks whether data was copied or entered accurately without transcription errors.

What are the primary advantages of a relational database over a file-based approach?

Relational databases reduce data redundancy, eliminate data inconsistency, decrease program-data dependency, allow enforced referential integrity, enable complex SQL queries, and provide customizable user access views.

What conditions must a database table satisfy to be in Third Normal Form (3NF)?

The table must be in 1NF (atomic values, primary key, no repeating groups), 2NF (no partial key dependencies on composite keys), and 3NF (no transitive dependencies where non-key attributes depend on other non-key attributes).

What are the main management tasks performed by an Operating System?

Memory management, file management, security management, hardware/device management, and process management.

What is a Dynamic Link Library (DLL) and what benefits does it offer?

A DLL is a shared library file loaded into memory at runtime for multiple programs. Benefits include smaller executable file sizes, lower RAM usage, and independent maintenance/updating without recompiling main applications.

What are the main differences between an Interpreter and a Compiler?

An interpreter translates and executes source code line-by-line (stopping at errors, making debugging easier but execution slower). A compiler translates the entire source code at once into an independent executable machine code file (faster execution, source code protected).

What are the four main software license types and their defining features?

Commercial (paid, closed source), Shareware (free trial period, paid afterwards, closed source), Open Source (free/accessible source code, editable and redistributable), and Free Software Foundation (free to run, study, modify, and share).

What is CSMA/CD and how does it manage network transmission on a bus topology?

Carrier Sense Multiple Access with Collision Detection listens to the channel before transmitting. If two devices transmit at once and collide, collision is detected, transmission stops, a jamming signal is sent, and devices wait a random period before retransmitting.

What are the key structural differences between IPv4 and IPv6 addresses?

IPv4 uses $32$-bit addresses split into $4$ denary octets ($0$ to $255$) separated by dots. IPv6 uses $128$-bit addresses split into $8$ hexadecimal groups ($0000$ to $\text{FFFF}$) separated by colons.

What is the difference between a public IP address and a private IP address?

A public IP address is assigned by an ISP, unique across the internet, accessible publicly, and used for internet communication. A private IP address is assigned by a local router, unique only within the LAN, and inaccessible directly from the internet.