MATSEC AM Computing flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Two's complement negation

Invert every bit of the number and then add one. This represents the negative of the original value in two's complement binary arithmetic.

De Morgan's laws

NOT(A AND B) equals NOT A OR NOT B, and NOT(A OR B) equals NOT A AND NOT B. These identities let designers replace gates and simplify Boolean expressions.

Amdahl's law

Speedup equals 1 divided by ((1 - f) + f/s), where f is the parallel fraction and s the improvement factor. The serial portion limits maximum gain.

Von Neumann architecture

A design storing program instructions and data in the same memory, fetched and executed sequentially by a processor. It enables general-purpose stored-program computers.

Cache locality

Temporal locality means recently used data is likely reused soon; spatial locality means nearby addresses are likely accessed. Both explain why caches improve average memory access time.

Pipeline hazard

A situation preventing the next instruction from executing in the following cycle. Data, control and structural hazards are resolved by forwarding, stalling or branch prediction.

Pass by reference

The callee receives the address of the caller's variable, so modifications through the parameter affect the original argument after the call returns.

Loop invariant

A condition true before and after every iteration of a loop. Proving initialisation, maintenance and termination establishes the algorithm's correctness formally.

Polymorphism

The ability of a single interface or superclass reference to invoke behaviour specific to the actual runtime object type, resolved dynamically during execution.

Big-O notation

An asymptotic upper bound describing how an algorithm's resource use grows with input size, ignoring constants and lower-order terms.

Third normal form

A relation is in 3NF when it is in 2NF and no non-key attribute depends transitively on the primary key, eliminating redundancy and update anomalies.

ACID properties

Atomicity, consistency, isolation and durability: guarantees that transactions complete fully or not at all, preserve constraints, do not interfere, and survive failure.

Binary search precondition

The array must be sorted and support random access. Each comparison halves the search space, giving O(log n) time.

Primary key

A column or minimal set of columns uniquely identifying each row in a relation. It must be unique and cannot contain null values.

TCP versus UDP

TCP is connection-oriented, reliable and ordered with acknowledgements and retransmission. UDP is connectionless with no delivery guarantee, suiting low-latency traffic.

Subnet mask

A bit pattern separating the network prefix from the host portion of an IPv4 address. A /24 mask leaves 254 usable host addresses.

DNS resolution

The process translating a domain name into an IP address by querying cached records and authoritative name servers in a hierarchy.

Symmetric encryption

A cipher using the same secret key to encrypt and decrypt. It is fast and suited to bulk data, but both parties must share the key securely.

Digital signature

A hash of a message encrypted with the sender's private key. Verification with the public key proves integrity, authenticity and non-repudiation.

SQL injection

An attack inserting malicious SQL through unsanitised input. Parameterised queries binding values separately from SQL text prevent it.

CIA triad

Confidentiality, integrity and availability: the three core security goals describing secrecy of data, protection from modification, and reliable access when needed.

Full adder

A combinational circuit adding three bits, two operands plus a carry-in. It outputs a sum bit and a carry-out, enabling multi-bit addition.

Recursion base case

A condition that stops recursive calls by returning a result directly. Without it, recursion continues until the call stack overflows.

Normalisation

Organising relations to reduce redundancy and update anomalies by applying successive normal forms, chiefly 1NF, 2NF and 3NF.

CSMA/CD

Carrier sense multiple access with collision detection: stations listen before transmitting, detect collisions, and retransmit after a random backoff interval.

Hash function

A one-way function mapping input of any length to a fixed-length digest. It should be deterministic, fast and collision-resistant for security use.

Multiplexer

A combinational circuit selecting one of several data inputs according to control lines and routing it to a single output.

Unit testing

Testing individual functions or classes in isolation with controlled inputs and expected outputs, usually automated and run frequently during development.

Foreign key

An attribute referencing the primary key of another relation, enforcing referential integrity by ensuring each value matches an existing key or is null.

IPv4 addressing

A 32-bit address divided into network and host portions by a prefix length. Private ranges require translation to reach the public internet.

Phishing

A social engineering attack using deceptive messages to trick recipients into revealing credentials or opening malicious attachments, exploiting trust rather than technical flaws.

Instruction cycle

The repeating sequence of fetching an instruction from memory, decoding it, executing the operation, and storing any result before the next fetch.