Fundamental Information Technology Engineer Examination — knowledge map
The 101 core concepts of Fundamental Information Technology Engineer Examination and how they connect. Click a node in the map above to explore related terms and prerequisites; the list below indexes every concept with its definition and links to its prerequisites and related concepts.
Concepts (101)
CIA triad
The three pillars of information security: Confidentiality, Integrity, Availability.
Related: The CIA triad (confidentiality, integrity, availability)
Radix conversion (binary and hexadecimal)
Converting a number expressed in one base into another base. Computers process data in binary, but because binary is long, values are often grouped four bits at a time and written compactly in hexadecimal (binary 1111 = hex F). Decimal-to-binary divides by 2 until the quotient is 0 and reads the remainders in reverse; binary-to-decimal multiplies each digit by its positional weight (…8, 4, 2, 1) and sums them.
Related: Binary number
Availability rate
The proportion of time a system operates correctly. Availability = MTBF ÷ (MTBF + MTTR); it rises as time-between-failures grows and repair time shrinks. A core availability metric, also used as an agreed SLA target (e.g., 99.9%).
Prerequisites: CIA triad、MTBF (mean time between failures)
Array and linked list
Fundamental data structures for holding multiple data items in sequence. An array places elements in a contiguous region and allows immediate O(1) access to any element by index, but inserting or deleting in the middle is costly because subsequent elements must shift. A (linked) list has each element hold a reference (pointer) to the next, so insertion and deletion only require re-linking pointers, but accessing an arbitrary element is O(n) because it must be traversed from the head.
Register
The fastest, smallest storage locations, located inside the CPU. They temporarily hold data being operated on, instructions, addresses, and execution state. Types include the program counter (address of the next instruction), the instruction register (the fetched instruction), and the accumulator (arithmetic results).
ACID
Properties of reliable transactions: Atomicity, Consistency, Isolation, Durability.
Authenticity
An extended element of information security ensuring that a user, piece of information, or process is genuinely what it claims to be, free of impersonation or forgery. Digital signatures and multi-factor authentication substantiate authenticity. It supplements the core CIA triad (confidentiality, integrity, availability) and appears in exam questions distinguishing the seven security elements.
Prerequisites: CIA triad、The CIA triad (confidentiality, integrity, availability)
Audit techniques and auditability
Audit techniques are methods a system auditor uses to gather audit evidence, including interviews, document review, on-site inspection, checklists, and computer-assisted audit techniques (CAATs, which use audit software or test data). Auditability is the property that a system is prepared to undergo an audit — that records of its processing and access (logs and audit trails) are in place.
Prerequisites: Array and linked list、System audit、Design review (walkthrough, inspection)
Linear search
A search method that examines elements one by one from the beginning of an array or list until the target value is found. It works on unsorted data, but has O(n) time complexity, making it slower than binary search.
Prerequisites: Array and linked list、Time complexity and Big-O notation、Radix conversion (binary and hexadecimal)
Related: Binary search
Memory hierarchy
An arrangement that combines storage devices of differing speed, capacity, and cost in tiers so the whole appears both fast and large. Upper tiers are faster, smaller, and costlier, ordered as registers → cache memory → main memory → secondary storage (SSD, hard disk). Cache memory bridges the CPU–main-memory speed gap, and virtual memory compensates for insufficient main-memory capacity.
Prerequisites: Register、Virtual memory and paging、Main memory and cache memory
Binary search
A search method for a sorted list of data that compares the target value with the value at the midpoint of the search range and repeatedly narrows the range by half. It requires the data to already be sorted, and it finds the target faster than a linear search.
Prerequisites: Radix conversion (binary and hexadecimal)
Related: Linear search
Copyright
A right that arises automatically the moment a work such as a novel, music, or a program is created; unlike a patent right, no registration procedure is required. Copyright in a program generally belongs to the person who created it, except in the case of a work made for hire.
Sampling and encoding
Digitizing an analog signal (A/D conversion) has three stages: sampling → quantization → encoding. Sampling extracts values at fixed intervals (the sampling period); by the sampling theorem the sampling frequency must be at least twice the signal's highest frequency to avoid aliasing. Quantization rounds each sampled value to a discrete level. Encoding then maps each quantized value to a binary bit pattern.
Prerequisites: Radix conversion (binary and hexadecimal)、Binary number
Tree structures and binary search trees
A hierarchical data structure made up of nodes and edges. A binary search tree is organized so that a node's left subtree holds smaller values and its right subtree holds larger values, enabling search, insertion, and deletion in average O(log n) time.
Prerequisites: Radix conversion (binary and hexadecimal)、Binary search
CI/CD
CI (continuous integration) automatically builds and tests code on every change to catch defects early. CD has two meanings: continuous delivery automates everything up to a release-ready state but keeps a manual approval for the production release, while continuous deployment automates all the way to production.
XP (Extreme Programming)
A leading agile development method that emphasizes iterative development by small teams and responsiveness to change. It is characterized by practices such as pair programming, test-driven development (TDD), refactoring, continuous integration, and small releases. Whereas Scrum centers on a framework for running the project, XP places emphasis on technical development practices.
Prerequisites: CI/CD、Agile development and Scrum
Injection countermeasures (placeholders, sanitizing)
A set of techniques for safely handling input to prevent SQL injection and XSS. A bind mechanism (placeholder) fixes the skeleton of an SQL statement first and then plugs in values as pure data, so input can never be interpreted as SQL commands — a fundamental countermeasure. Sanitizing (escaping) converts special characters such as `<` and `'` into harmless representations so they are not interpreted as commands, and is used as an output-time countermeasure against XSS.
Related: SQL injection
Logic circuit
A digital circuit that performs logic operations on signals represented as binary 0/1 by combining logic gates such as AND, OR, and NOT. Logic circuits are broadly divided into combinational circuits, whose output depends only on the current inputs, and sequential circuits, which contain memory elements such as flip-flops and therefore also depend on past state. They form the basis of a computer's arithmetic and control circuitry.
Prerequisites: Flip-flop、Radix conversion (binary and hexadecimal)、Binary number
SQL injection
An attack technique that injects malicious SQL fragments into a web application's input fields to manipulate or view a database in unintended ways. It is prevented by using bind variables (placeholders) and validating input values.
Related: Injection countermeasures (placeholders, sanitizing)
Cross-site scripting (XSS)
An attack technique that injects malicious script into a vulnerable website so it executes in a visitor's browser, potentially leading to cookie theft or a spoofed display. Escaping (sanitizing) output is the basic countermeasure.
Prerequisites: Injection countermeasures (placeholders, sanitizing)
Foreign key
A column referencing another table’s primary key to relate tables; preserves referential integrity.
Prerequisites: Primary key
Binary number
A way of representing numbers using only the two digits 0 and 1. Because a computer's internals correspond to the on/off states of electrical signals, binary is the basic representation used internally; converting between binary and decimal is a fundamental skill tested.
Main memory and cache memory
Main memory is the storage area for programs and data that the CPU reads and writes directly. Cache memory is faster but smaller-capacity memory that bridges the speed gap between the CPU and main memory, speeding up processing.
Malware
A collective term for malicious software created to harm users, including viruses, worms, trojan horses, and ransomware. Infection routes are varied, including email attachments, visiting malicious sites, and USB drives.
Related: Types of malware (virus, worm, trojan horse, spyware)
Requirements definition
An upstream software development process step that clarifies the functions and performance the users or client require and fixes the scope of what will be built. Misunderstandings here directly translate into costly rework in later stages.
MTBF (mean time between failures)
For a repairable system, the average operating time from one failure to the next. A larger value means fewer failures and higher reliability. Computed as total operating time ÷ number of failures.
Man-in-the-middle (MITM) attack
A general term for an attack in which the attacker inserts themselves between two communicating parties, making each believe it is communicating directly with the other, while eavesdropping on or tampering with the traffic. Techniques used to set it up include ARP spoofing, gateway impersonation via a rogue DHCP server, and DNS cache poisoning. Countermeasures include mutual authentication (e.g., verifying digital certificates) and encrypting/integrity-protecting the communication path.
Consistency
One of the ACID properties, guaranteeing that a database always satisfies its defined constraints, such as uniqueness or referential integrity, both before and after a transaction. It prevents transitions to contradictory data states and maintains the correctness of business data.
Prerequisites: ACID
Isolation
One of the ACID properties, ensuring that concurrently executed transactions produce results as if each ran independently without interference from others. The isolation level setting controls how much anomalous behavior, such as dirty reads, is permitted.
Prerequisites: ACID
Deep learning
Methods using multi-layer neural networks; strong on complex data like images, audio, and language.
Availability management (service management)
A management activity aimed at keeping an IT service usable whenever users need it. It designs and monitors measures such as eliminating single points of failure, adding redundancy, and planning maintenance so that availability (uptime rate) meets its targets. Availability is expressed as MTBF ÷ (MTBF + MTTR) and improves by lengthening the interval between failures and shortening repair time.
Prerequisites: Availability rate、CIA triad、MTBF (mean time between failures)
Time complexity and Big-O notation
An indicator of how an algorithm's running time or memory usage grows as a function of input size n. Expressed as O(1), O(log n), O(n), O(n log n), O(n^2), and so on, it is used to compare the efficiency of algorithms.
Hit rate and access time (effective access time)
The hit rate is the fraction of data requests the CPU can satisfy from cache memory; the remaining fraction is the miss rate (= 1 − hit rate). Effective access time is computed as (hit rate × cache access time) + (miss rate × main-memory access time); a higher hit rate shortens the average access time and speeds up processing.
Prerequisites: Main memory and cache memory
CISC and RISC
Two philosophies of CPU instruction set design. CISC has complex, multi-function instructions that do a lot per instruction, often taking several clock cycles each. RISC restricts itself to simple instructions executed in roughly one clock cycle each, using pipelining for speed.
Prerequisites: Pipeline processing
CNN (convolutional neural network)
A deep learning model that combines convolutional layers and pooling layers to progressively extract spatial features such as those in images. It is a leading architecture for high-performance image recognition and object detection.
Prerequisites: Deep learning
Floating-point number
A format for representing real numbers using a sign, exponent, and mantissa (IEEE 754 is the representative standard). It can handle a wide range of values, but cannot represent some decimal fractions exactly, leading to rounding errors.
Related: Floating-point errors (rounding, cancellation, loss of trailing digits)
Floating-point errors (rounding, cancellation, loss of trailing digits)
Because floating-point numbers hold only a finite number of digits, several errors arise during computation. A rounding error comes from truncating (e.g., rounding) low-order digits that cannot be represented. Cancellation (loss of significance) is the sharp drop in significant digits when subtracting two numbers of nearly equal magnitude. Loss of trailing digits occurs when adding or subtracting numbers of vastly different magnitudes, so the smaller value is rounded away and never reflected in the result.
Related: Floating-point number
Instruction cycle (fetch/decode/execute/store)
The basic repeating cycle by which a CPU processes one machine-language instruction: fetch (retrieve the instruction from main memory) → decode (interpret it) → execute (perform the operation) → store (write the result back to a register or main memory). Overlapping these stages across multiple instructions is what pipeline processing does.
Prerequisites: Pipeline processing、Register
Inventory management
Management to maintain an appropriate inventory level, curbing both lost sales from stockouts and holding costs from excess stock. It uses methods such as the reorder-point system, which orders when stock falls to a set level, and the economic order quantity (EOQ), which finds the order size that minimizes the sum of per-order and holding costs.
Types of malware (virus, worm, trojan horse, spyware)
Common classifications of malware. A virus parasitizes other programs or files and spreads when its host is executed. A worm needs no host and self-replicates to propagate autonomously across networks. A trojan horse disguises itself as a harmless legitimate program to intrude and performs malicious actions internally without self-replicating. Spyware secretly collects information without the user noticing and sends it to an external party.
Related: Malware
Normal forms (1NF to 3NF)
A staged technique for reducing redundancy and update anomalies in relational database design. First normal form removes repeating groups, second normal form separates attributes that depend on only part of the primary key, and third normal form separates attributes that depend on non-key attributes (transitive dependency).
Prerequisites: Primary key
Organizational structure
The form of organization a company adopts to carry out its business. Types include the functional organization, which divides departments by kind of work; the divisional organization, structured into self-contained units by product or region; and the matrix organization, which combines functional and business axes in a grid — chosen according to business strategy and scale.
Page fault and thrashing
A page fault is an interrupt that occurs when a page needed under virtual memory is not present in main memory; processing pauses while the page is loaded (paged in) from secondary storage. When too many pages are needed at once for the installed memory, page swapping (paging) happens so frequently that the CPU spends most of its time waiting on I/O and throughput collapses—this state is called thrashing.
Prerequisites: Virtual memory and paging
Password attacks (brute-force, dictionary, list-based)
A collective term for attacks that illegitimately determine someone's password. A brute-force attack tries every possible combination of characters in turn. A dictionary attack prioritizes dictionary words and commonly used strings. A list-based (credential-stuffing) attack tries ID/password pairs leaked from other services against users who reuse them. Long, complex passwords, avoiding reuse, multi-factor authentication, and account lockout are countermeasures.
Prerequisites: Array and linked list
Pseudocode (Subject B)
A language-independent notation used in Subject B of the FE exam. It expresses variable declarations, branching, loops, and function calls in a common syntax, and is used to test tracing algorithms and filling in blanks.
Sorting algorithms (bubble, quick, merge sort)
A family of algorithms for rearranging data into a defined order. Bubble sort repeatedly swaps adjacent elements — simple but O(n^2); quick sort partitions around a pivot for an average O(n log n); merge sort uses divide-and-conquer to reliably guarantee O(n log n) while remaining stable.
Stack and queue (abstract data structures)
Fundamental data structures that impose an order on inserting and removing data. A stack manages elements last-in-first-out (LIFO), and a queue manages them first-in-first-out (FIFO); both frequently appear as building blocks in pseudocode programs.
Prerequisites: Pseudocode (Subject B)、Queue (FIFO)、Stack (LIFO)
Virtual memory and paging
A technique that lets programs larger than physical main memory be executed. A program is divided into fixed-size "pages," only the needed pages are loaded into main memory, and pages no longer needed are swapped out to secondary storage (paging).
WAF (Web Application Firewall)
A defense appliance or service that inspects the contents of HTTP/HTTPS traffic to detect and block attacks aimed at the web application layer, such as SQL injection and cross-site scripting (XSS). Unlike an ordinary firewall that filters by destination port or IP, a WAF examines the actual request content (parameters, etc.) of the application to make its decisions.
Prerequisites: SQL injection、Cross-site scripting (XSS)、HTTPS
HTTPS
HTTP carried on top of TLS. Unlike plain HTTP, the traffic is encrypted, preventing eavesdropping or tampering along the path. Browsers verify the certificate to confirm the server's legitimacy, and it's now the standard way sites communicate.
Infrastructure as Code (IaC)
Defining infrastructure declaratively as code (templates) so it is reproducible and version-controlled—preventing manual drift and enabling review, automation, and consistent multi-environment builds. On AWS, CloudFormation and CDK are the main tools.
Prerequisites: Version control system (VCS)
Agile development and Scrum
Agile development is an umbrella term for development approaches that repeat short cycles (iterations) of planning, design, implementation, and testing to respond flexibly to changing requirements. Scrum is a representative agile method that repeats short cycles called sprints.
BPR (Business Process Reengineering)
An effort that fundamentally re-examines and redesigns business processes, organizational structure, and information systems from the ground up, without assuming existing organizational rules — distinct from incremental improvement (kaizen).
Prerequisites: Organizational structure
DevOps
A philosophy and culture in which development and operations collaborate closely, using automation and CI/CD to deliver software faster and continuously.
Prerequisites: CI/CD
DHCP
A protocol that automatically assigns the network settings a device needs — including an IP address — when it connects to the network, saving an administrator the trouble of manually configuring an IP address on every device.
Industrial property rights
A collective term for four rights: patent, utility model, design, and trademark rights. Unlike copyright, obtaining these rights requires application to and registration with the patent office.
Prerequisites: Copyright
Intellectual property rights
A collective term for rights that protect creative outcomes such as inventions, works of authorship, designs, and trademarks. It is broadly divided into copyright and industrial property rights (patent, utility model, design, and trademark rights).
Prerequisites: Copyright、Industrial property rights
Internal control
The mechanisms and structures a company builds into its own business processes so that operations are carried out appropriately and efficiently. It aims to prevent fraud and ensure reliable financial reporting, and responsibility for establishing and operating it rests with management.
MOT (Management of Technology)
A management approach used by technology-based businesses to continuously translate the outcomes of technological development into business results and increased corporate value.
Non-functional requirements
Requirements concerning the quality aspects of a system — such as performance, availability, security, and maintainability — rather than the functions themselves. They must be clarified alongside functional requirements during requirements definition.
Prerequisites: CIA triad、Requirements definition
Phishing
A fraud technique that lures victims to fake emails or websites impersonating real companies or financial institutions, in order to steal IDs, passwords, or credit card information. Carefully checking the URL and domain is a basic countermeasure.
Queue (FIFO)
A data structure in which the first item stored is the first one retrieved (FIFO: First In First Out). Items enter at one end (the rear) and leave from the other end (the front). It is often likened to a line of people waiting at a counter.
RASIS
An acronym for five metrics used to measure the dependability of a system: Reliability, Availability, Serviceability, Integrity, and Security.
Prerequisites: CIA triad
SLA and SLM
An SLA (service level agreement) is a document agreed between a service provider and its users specifying quality targets such as uptime and response time. SLM (service level management) is the ongoing activity of monitoring and reviewing that agreement.
Prerequisites: Availability rate
Technology roadmap
A time-based visualization of future technology trends and a company's own technology-development plans. It is used in MOT (management of technology) to align R&D investment decisions with business strategy.
Prerequisites: MOT (Management of Technology)
Primary key
A column that uniquely identifies each row; no duplicates or nulls.
Design review (walkthrough, inspection)
An activity in which stakeholders verify design artifacts to find errors and problems early. A walkthrough is an informal review in which the author leads by explaining the artifact while participants point out issues, with light preparation. An inspection is a formal review led by a moderator with roles assigned to participants, systematically detecting and recording defects against a checklist, giving high detection power. The architect chooses the review form by the importance of the target to prevent defects leaking into later phases.
Prerequisites: Array and linked list
SLA (service level agreement)
A contract defining guaranteed uptime; if missed, you may be eligible for service credits (partial refunds).
Prerequisites: Availability rate
Subnet mask
A value marking the boundary between the network and host portions of an IP address (e.g., 255.255.255.0)—the dotted-decimal counterpart to a CIDR prefix length, still used in on-prem network gear and some cloud configuration screens.
Prerequisites: CIDR notation
DoS/DDoS attack
An attack that overloads a server or network with a flood of requests or malformed packets so that legitimate users cannot use the service (DoS = denial of service). A DDoS (distributed DoS) launches the attack simultaneously from many devices infected with malware (a botnet), so the sources are dispersed and cannot be stopped by simply blocking one source. It harms availability rather than the confidentiality of information.
Flip-flop
A basic sequential-circuit element that can hold one bit of information. It latches its input in sync with a clock signal and holds the output until the next clock, serving as a building block for registers, counters, and other memory circuits.
Prerequisites: Register
Hashing
A data structure technique that uses the value produced by applying a hash function to a key as the storage position in an array, achieving average O(1) search and insertion. It requires a way to handle collisions, where different keys map to the same position.
Prerequisites: Array and linked list、Hash function (tamper detection)
Pipeline processing
A technique that divides instruction execution into stages such as fetch, decode, execute, and write-back, processing the stages of multiple instructions concurrently to increase CPU throughput. Branch instructions and similar cases can cause pipeline hazards.
The CIA triad (confidentiality, integrity, availability)
The three fundamental elements of information security management. Confidentiality means only authorized people can access information; integrity means information is accurate and has not been tampered with; availability means information can be accessed whenever it is needed.
Related: CIA triad
Digital signature
A technology that uses public-key cryptography to prove both that an electronic document was created by the claimed author (authenticity) and that the document has not been tampered with (integrity).
Prerequisites: Authenticity、CIA triad
Lossless and lossy compression
Lossless compression can fully restore the original data. Lossy compression achieves a higher compression ratio by discarding information that is hard for humans to perceive, but the original data cannot be perfectly restored — image or audio quality degrades slightly.
POS system
A point-of-sale (Point Of Sale) system that records product codes, quantities, and the time of sale at the moment a product is sold at the register, and uses that data for inventory management and sales-strategy analysis.
Prerequisites: Inventory management、Register
Primary key and foreign key (relational DB)
A primary key is the column (or combination of columns) that uniquely identifies a row within a table. A foreign key is a column that references another table's primary key, implementing the relationship between tables.
Prerequisites: Foreign key、Primary key
Stack (LIFO)
A data structure in which the last item stored is the first one retrieved (LIFO: Last In First Out). Items are added and removed only from one end (the top). It is often likened to a browser's "back" history.
System audit
An activity in which an independent auditor verifies and evaluates, from a third-party standpoint, whether an information system is operated safely and efficiently, and advises on improvements. Independence from the audited department is a precondition for the audit's credibility.
Waterfall model
A development approach that proceeds through phases — requirements definition, design, implementation, testing — in sequence, on the premise that, in principle, work does not return to a previous phase. It is easy to plan but not well suited to mid-project requirement changes.
Prerequisites: Requirements definition
MTTR (mean time to repair)
The average time from a failure until recovery. A smaller value means faster recovery and better maintainability. Computed as total repair time ÷ number of failures; it is part of the denominator in availability = MTBF ÷ (MTBF + MTTR), assessed together with MTBF (mean time between failures) for reliability and maintainability.
Prerequisites: Availability rate、MTBF (mean time between failures)
Version control system (VCS)
A system that records the history of file changes, enabling revert, tracing who/why, and collaboration.
Barrier-free
The idea of removing elements that act as barriers for elderly people or people with disabilities so they can use products more easily. Unlike universal design, which aims from the outset to be usable by many, it focuses on eliminating specific barriers for particular users after the fact.
Related: Universal design
Competitive strategy
A collective term for strategies to gain advantage over competitors. Using methods such as SWOT and five-forces analysis, PPM, and core-competence management to analyze markets and rivals, it aims to establish a sustainable competitive advantage through cost leadership or differentiation.
Prerequisites: SWOT analysis
Hash function (tamper detection)
A function that computes a fixed-length value (a hash value) from data of arbitrary length. The same input always produces the same output, and even a tiny change drastically alters the value, which is why hash functions are used for tamper detection and password storage.
Hybrid cryptography
A scheme that combines the processing speed of symmetric-key cryptography with the secure key distribution of public-key cryptography. The data itself is encrypted with a symmetric key, and that symmetric key is then encrypted with the recipient's public key before being sent. Used in S/MIME, PGP, and TLS 1.2 and earlier (note that current TLS 1.3 uses (EC)DHE key exchange and no longer sends a symmetric key encrypted under a public key).
Prerequisites: Symmetric-key cryptography
Sort stability (stable sort)
The property that, when two elements have equal sort keys, their relative order before sorting is preserved after sorting. Merge sort is a stable sort, whereas quick sort can be unstable depending on the implementation.
Prerequisites: Sorting algorithms (bubble, quick, merge sort)
Task (process) management
An OS function that manages tasks (processes)—the units of running programs. Each task transitions among three states: running (using the CPU), ready (prepared but waiting its turn for the CPU), and waiting/blocked (awaiting an event such as I/O completion). The OS dispatcher allocates CPU time to a ready task and switches between them using scheduling policies such as round-robin or priority, giving the appearance of running multiple tasks concurrently.
Arrow diagram
A diagram (PERT chart) that represents the sequencing of tasks and their durations using arrows and nodes. Summing the durations along each path allows the critical path and the earliest/latest start and finish dates to be calculated.
Prerequisites: Critical path
Critical path
Among all the paths from a project's start to its finish, the one with the longest duration. If any task on this path slips by even one day, the overall project completion date slips as well.
Generative AI
AI capable of generating new content such as text, images, audio, or program code. While useful for improving operational efficiency, care is needed regarding risks such as hallucination — plausibly generating incorrect information — and copyright infringement.
Prerequisites: Copyright
JPEG and MPEG
JPEG is a representative image format that lossily compresses still images such as photographs. MPEG is a representative family of standards for compressing video (image plus audio), reducing data volume by exploiting differences between frames.
Prerequisites: Lossless and lossy compression
Role of the OS (operating system)
Basic software positioned between hardware and application software, responsible for memory management, task management, file management, and input/output control. Applications access hardware through the functions the OS provides.
Prerequisites: Task (process) management
Segregation of duties
A basic internal-control principle that prevents fraud and error by dividing a sequence of duties — such as approval, execution, recording, and custody — among multiple people rather than concentrating them in one person.
Prerequisites: Internal control
SWOT analysis
An analysis method that organizes a company's internal factors — strengths and weaknesses — alongside external environmental factors — opportunities and threats — to support the formulation of business strategy.
Symmetric-key cryptography
An encryption method that uses the same key (a shared secret key) for both encryption and decryption. Processing is fast, but the key must be shared securely with each communication partner, making key management increasingly complex as the number of partners grows.
Transactions and ACID properties
A transaction is a unit that treats a series of operations as a single whole; if it fails partway through, the entire transaction is undone (rolled back). The ACID properties — atomicity, consistency, isolation, and durability — are the four qualities a transaction must satisfy.
Prerequisites: ACID
Universal design
A design philosophy that aims to make products and environments usable by as many people as possible, regardless of differences in age, disability, language, or culture — a broader scope than barrier-free design, which addresses specific groups of users.
Related: Barrier-free
CIDR notation
A notation expressing an IP address range by prefix length, like “/24” (256 addresses) or “/16” (65,536 addresses)—the smaller the number, the larger the range. It underlies network design across every cloud: sizing VPCs/VNets and subnets, longest-prefix-match routing, and scoping firewall-rule allows.