Tech Glossary

Definitions for the technical terms used across TechCompare's calculators and comparisons. Each term links to the tool or comparison page where you can compute or explore it in detail.

Displays

PPI (Pixels Per Inch)

A measure of pixel density: the number of pixels per linear inch of a display. Higher PPI means smaller pixels and a sharper image, but only matters if you sit close enough to see the difference.

Retina distance

The minimum viewing distance at which the human eye can no longer resolve individual pixels, approximated as 3438 divided by the display's PPI. Sit further than this and the screen looks pixel-perfect.

Refresh rate (Hz)

How many times per second a display redraws its image, measured in Hertz. A 144Hz monitor refreshes 144 times per second, once every 6.9 ms, against 16.7 ms for a 60Hz panel.

Display Stream Compression (DSC)

A visually lossless compression format standardized by VESA that cuts display bandwidth roughly 3:1, letting modern cables drive 4K 240Hz or 8K 60Hz over existing connectors.

Chroma subsampling (4:4:4, 4:2:2, 4:2:0)

A bandwidth-saving technique that reduces color resolution. 4:4:4 carries full color per pixel, 4:2:0 halves both horizontal and vertical color resolution, cutting bandwidth by about 50%.

Monitor curvature (1000R, 1500R, 1800R)

The radius in millimeters of a curved monitor's arc. A lower number means a tighter curve, so 1000R is tighter than 1800R.

Aspect ratio

The proportional relationship between a display's width and height, written as width:height. 16:9 is the common monitor and TV format, 21:9 is the ultrawide format, 32:9 is super ultrawide, and 3:2 or 16:10 are taller ratios favored for productivity laptops.

Ultrawide monitor

A monitor with a 21:9 aspect ratio, roughly 34% wider than a standard 16:9 panel. Common specs include 3440x1440 at 34 inches (86 cm). Provides extra horizontal real estate for productivity and a wider field of view in supported games. The 32:9 super ultrawide format is twice the width of a 16:9 panel.

Field of view (FOV)

How much of your peripheral vision a screen occupies at a given viewing distance, measured in degrees. THX uses a 40-degree FOV as a home-theater immersion reference. The historical SMPTE EG 18-1994 document used 30 degrees as a theater reference, but SMPTE withdrew it in 2003. Wider aspect ratios in supported games also extend the in-game FOV horizontally.

THX vs SMPTE

Two commonly cited viewing references. THX uses a 40-degree horizontal field of view for cinema immersion (sit at about 1.2 times the screen diagonal). The historical SMPTE EG 18-1994 document used a 30-degree theater angle (about 1.6 times the diagonal), but SMPTE withdrew it in 2003 and no longer endorses its content as a current everyday-viewing rule.

Memory

CAS Latency (CL)

The delay in clock cycles between a memory controller requesting a column of data and the RAM delivering it. Lower CL means less waiting, but true latency also depends on the clock speed.

True latency (ns)

The real-world delay of RAM in nanoseconds, calculated as (CL x 2000) / data rate. It lets you compare kits across DDR3, DDR4, and DDR5 on equal footing.

MT/s (Megatransfers per second)

The data rate of DDR memory, measuring how many million data transfers happen per second. DDR5-6000 runs at 6000 MT/s, which is 3000 MHz internal clock due to double data rate.

JEDEC vs XMP/EXPO

JEDEC is the default conservative memory profile every DIMM boots with. XMP (Intel) and EXPO (AMD) are overclocking profiles stored on the DIMM that you enable in BIOS to unlock advertised speeds.

TDP (Thermal Design Power)

The amount of heat a CPU or GPU cooling system must dissipate, rated in watts. TDP correlates with power draw but is not identical to it: a 250W TDP chip usually draws roughly 250W under full load, but modern CPUs can boost briefly above their rated TDP, and idle draw is far lower.

Kilowatt-hour (kWh)

The unit utilities use to bill electricity: one kilowatt-hour is 1,000 watts drawn for one hour. Annual cost of any device is (watts x hours per day x 365 / 1,000) x price per kWh. A 100W device left on 24/7 at €0.30/kWh costs €263/year.

L1, L2, L3 cache

The three tiers of CPU cache, smallest and fastest first. L1 is ~1 ns and per-core, L2 is ~3-5 ns and per-core, L3 is ~10-15 ns and shared across cores. Cache hits avoid the 50-80 ns round-trip to DDR5 RAM.

Storage

RAID 5

A RAID level using single distributed parity across N drives. Usable capacity is (N - 1) x drive size. It tolerates one drive failure and is a common NAS configuration.

RAID 6

A RAID level using double distributed parity. Usable capacity is (N - 2) x drive size. It tolerates two simultaneous drive failures, making it safer for large arrays with long rebuild times.

RAID 10

A RAID level that mirrors then stripes data (RAID 1+0). Usable capacity is 50% of raw storage. Writes don't pay a parity penalty, so random-write performance is good. It tolerates up to N/2 failures if they hit different mirror pairs.

Parity

Error-correcting data stored across drives in RAID 5 and 6. Parity lets the array rebuild lost data from a failed drive, but calculating it imposes a write penalty on every update.

NVMe vs SATA

Two SSD interfaces. NVMe connects over PCIe and reaches 3,000-14,000 MB/s for sequential reads. SATA is the legacy 6 Gbps interface shared with HDDs and tops out around 550 MB/s. NVMe also has lower random-read latency and handles many more requests at once, which is what makes an NVMe SSD feel faster than a SATA SSD in real workloads.

Networking

CIDR notation

Classless Inter-Domain Routing notation, a shorthand for subnet masks. /24 means the first 24 bits are the network, leaving 8 bits for hosts. /24 gives 254 usable IPv4 addresses.

Subnet mask

A 32-bit number that divides an IP address into network and host portions. 255.255.255.0 is the mask for a /24 subnet, meaning the last octet is available for host addresses.

Broadcast address

The last IP address in an IPv4 subnet, used to send data to all devices on that network segment simultaneously. IPv6 has no broadcast, using multicast instead.

Gigabit Ethernet

A network standard carrying 1 billion bits per second (1000 Mbps, or about 125 MB/s in real-world file transfers). It's a common wired speed in homes and small offices.

Bandwidth-delay product

The amount of data a network connection must have in flight at once to fill the link, calculated as link speed multiplied by round-trip time. For a 1 Gbps link at 100 ms RTT it is about 12.5 MB. When the TCP receive window is smaller than the bandwidth-delay product, throughput collapses to window size divided by RTT rather than the link rate.

TCP window scaling

An RFC 1323 TCP option that lets the receive window grow beyond the 64 KB hard cap by left-shifting the advertised 16-bit window value, up to a 1 GiB maximum. Without it, long-distance transfers on fast links are bottlenecked by the bandwidth-delay product because the unscaled window is far smaller than the link can carry.

Developer

Cron expression

A 5-part scheduling string used by Unix cron, AWS EventBridge, and Kubernetes CronJobs. The fields are minute, hour, day of month, month, and day of week, read left to right.

Unix timestamp

The number of seconds since January 1, 1970 (the Unix epoch). It's a common way to store time in programming, and 32-bit systems hit the year 2038 problem when the value overflows.

Base64 encoding

An encoding that writes binary data as 64 printable ASCII characters. It's used to embed binary data in JSON, URLs, and email, and it adds about 33% to the size.

JSON (JavaScript Object Notation)

A lightweight data-interchange format using human-readable text to store and transmit structured objects. It's widely used for web APIs and configuration files.

Open Graph (og:) tags

A set of <meta> tags in your HTML <head> that control how a page renders as a link preview card when shared on Facebook, LinkedIn, Discord, Slack, and most chat apps. The four required properties are og:title, og:type, og:image, and og:url. og:description is optional metadata that is still widely recommended. Twitter has its own twitter:card tags but falls back to og: when those are missing.

LLM token

The unit a large language model reads and bills text in. A token is usually a common word, part of a longer word, or a piece of punctuation, averaging about four characters or three-quarters of a word per token in English. Each model family has its own tokenizer, so the same input produces different token counts across GPT, Llama, Claude, and Gemini.

Byte Pair Encoding (BPE)

The tokenization algorithm used by GPT, Llama, and many other LLMs. BPE builds a vocabulary by iteratively merging the most frequent adjacent byte pairs in a training corpus, so common sub-words become single tokens and rare words split into multiple tokens. The tokenizer is what determines exact token counts for a given input.

Security

Entropy (passwords)

A measure of password unpredictability in bits. A 16-character password from a 90-character alphabet has about 104 bits of entropy, well beyond brute-force reach for modern hardware.

CSPRNG

Cryptographically Secure Pseudo-Random Number Generator. The browser's crypto.getRandomValues() is a CSPRNG backed by OS entropy, suitable for generating real passwords and API keys.

JWT (JSON Web Token)

A compact token made of a header, a payload of claims and a signature, each written in Base64url and joined by dots. Anyone can read the claims, so a server only trusts a JWT after checking its signature with the issuer's key and checking claims like exp, iss and aud.

chmod (file permissions)

A Unix command that changes file permissions using octal notation (like 755) or symbolic notation (like rwxr-xr-x). The three digits apply to owner, group, and public respectively.

WCAG contrast ratio

A ratio measuring the luminance difference between foreground and background text, from 1:1 (no contrast) to 21:1 (max). WCAG AA requires 4.5:1 for normal text, AAA requires 7:1.

Audio

Frequency (Hz)

The number of cycles per second a sound wave completes, measured in Hertz. Human hearing nominally spans 20 Hz at the low bass end up to 20,000 Hz at the high treble end. Pitch rises with frequency, so each doubling of Hz is one octave higher.

Waveform (sine, square, triangle, sawtooth)

The shape of a periodic sound wave. A sine is a single pure pitch with no overtones, a square adds odd harmonics and sounds buzzy, a triangle has softer odd harmonics, and a sawtooth contains both odd and even harmonics for a bright, rich tone. The fundamental frequency stays the same across all four at a given Hz value.

Beat frequency

The slow amplitude pulsing you hear when two tones of nearly equal frequency play together. Two sines at 440 Hz and 444 Hz produce a beat at 4 Hz, a slow wobble 4 times per second. The beat equals the absolute difference between the two source frequencies.

A4 (440 Hz)

The standard musical pitch reference: the A above middle C tuned to 440 Hertz. Many orchestras, tuners, and instruments use A4 = 440 Hz as the tuning standard, also known as concert pitch or A440.

Human hearing range

The nominal frequency range a healthy ear can perceive, about 20 Hz to 20,000 Hz. Most adults top out closer to 15 to 17 kHz after childhood, and the lowest tones are felt more than heard. Frequencies above 20 kHz are called ultrasound and below 20 Hz infrasound.

Web Audio API

A browser API for real-time audio synthesis and processing. It builds a graph of AudioNodes (oscillators, gain nodes, compressors) connected to an output destination. The Frequency Generator uses it to generate pure tones entirely client-side, with no server or audio files involved.