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.
Open the tool ➜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.
Open the tool ➜Refresh rate (Hz)
How many times per second a display redraws its image, measured in Hertz. A 144Hz monitor refreshes 144 times per second, producing smoother motion than a 60Hz panel.
Open the tool ➜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.
Open the tool ➜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%.
Open the tool ➜Monitor curvature (1000R, 1500R, 1800R)
The radius in millimeters of a curved monitor's arc. A lower number means a tighter curve. 1000R matches the human eye's natural focal distance, 1800R is a gentler curve.
Open the tool ➜Aspect ratio
The proportional relationship between a display's width and height, written as width:height. 16:9 is the universal monitor and TV standard, 21:9 is the ultrawide format, 32:9 is super ultrawide, and 3:2 or 16:10 are taller ratios favored for productivity laptops.
Open the tool ➜Ultrawide monitor
A monitor with a 21:9 aspect ratio, roughly 33% wider than a standard 16:9 panel. Common specs include 3440x1440 at 34 inches. 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.
Open the tool ➜Field of view (FOV)
How much of your peripheral vision a screen occupies at a given viewing distance, measured in degrees. THX recommends a 40-degree FOV for home theater immersion, SMPTE recommends 30 degrees for mixed everyday content. Wider aspect ratios in supported games also extend the in-game FOV horizontally.
Open the tool ➜THX vs SMPTE
Two standards for optimal viewing distance. THX specifies a 40-degree horizontal field of view for cinema immersion (sit at about 1.2 times the screen diagonal). SMPTE specifies a 30-degree angle for comfortable everyday viewing (sit at about 1.6 times the diagonal) to reduce eye fatigue on long sessions.
Open the tool ➜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.
Open the tool ➜True latency (ns)
The real-world delay of RAM in nanoseconds, calculated as (CL x 2000) / data rate. This is the only number that lets you compare kits across DDR3, DDR4, and DDR5 on equal footing.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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, which dominates real-world CPU performance.
Open the tool ➜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 the most common NAS configuration.
Open the tool ➜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.
Open the tool ➜RAID 10
A RAID level that mirrors then stripes data (RAID 1+0). Usable capacity is 50% of raw storage. It offers the best random-write performance of any RAID level and tolerates up to N/2 failures if they hit different mirror pairs.
Open the tool ➜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.
Open the tool ➜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 random-read latency is also roughly 12x lower, which is what makes an NVMe SSD feel faster than a SATA SSD in real workloads.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜Gigabit Ethernet
A network standard carrying 1 billion bits per second (1000 Mbps, or about 125 MB/s in real-world file transfers). It is the most common wired networking speed in homes and small offices.
Open the tool ➜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 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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜Unix timestamp
The number of seconds since January 1, 1970 (the Unix epoch). It is the standard way to represent time in programming, and rolls over in the year 2038 problem on 32-bit systems.
Open the tool ➜Base64 encoding
A binary-to-text encoding that represents binary data as 64 printable ASCII characters. It is used to embed binary data in JSON, URLs, and email, expanding the size by about 33%.
Open the tool ➜JSON (JavaScript Object Notation)
A lightweight data-interchange format using human-readable text to store and transmit structured objects. It is the de facto standard for web APIs and configuration files.
Open the tool ➜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.
Open the tool ➜Byte Pair Encoding (BPE)
The tokenization algorithm used by GPT, Llama, and most modern 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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜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, giving a slow wobble roughly four times per second. The beat equals the absolute difference between the two source frequencies.
Open the tool ➜A4 (440 Hz)
The standard musical pitch reference: the A above middle C tuned to 440 Hertz. Modern orchestras, tuners, and instruments use A4 = 440 Hz as the universal tuning standard, also known as concert pitch or A440.
Open the tool ➜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.
Open the tool ➜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.
Open the tool ➜