Zener diode

See diode.

zero-day exploit

A malware attack that targets a vulnerability not yet corrected or, in the worst cases, not yet recognized by the developer of the vulnerable software.

ZIF

Zero Insertion Force. A type of chip socket that allows the chip to drop into place without any pressure.

ZigBee

A short-range, low-power wireless network standard based on IEEE 802.15.4. It accepts up to 255 devices at distances of 1-100m (nominally 10m). One device acts as network coordinator, implying a star topology, but peer-to-peer links are possible. Data packets are up to 128 bytes, with variable payload up to 104 bytes.

Zigbee has 27 channels; two devices using the same channel resolve conflicts with CSMA/CD. Channel 0, at 868.3 MHz (Europe), uses 20 kb/s BPSK with DSSS. Channels 1-10, centered at 915 MHz with 2 MHz spacing (Americas), use 40 kb/s BPSK and DSSS. Channels 11-26, in the ISM frequency band between 2.4 and 2.4835 GHz with 5 MHz spacing (global), use 250 kb/s OQPSK.

ZigBee is less popular than other short-range wireless standards such as the low-energy version of Bluetooth. A major reason is that its software-configurable device profiles are not guaranteed to work together.

Zilog

Manufacturers of the Z80 series of 8-bit microprocessors used in some early PCs. They still make 8- and 16-bit microcontrollers.

ZKP

Zero-Knowledge Proof. A cryptographic technique that allows users to prove knowledge of some restricted information, e.g., a user identity, without having to reveal it. It can potentially support authentication while retaining anonymity.

ZMA

See cable connector.

Zmodem

See data protocol.

zombie

In computer security, a computer controlled by a bot program. See malware. Can also mean a software process that terminated incorrectly and so is still running.

Z-RAM

Zero-capacitor Random Access Memory. A volatile memory technology announced in 2010, envisioned as a CPU cache memory but not commercially successful. It dispenses with capacitors for charge retention, using the presence or absence of floating positive charge on a drained transistor to represent a 1 or 0. It uses very low voltage, and newer versions can be built on conventional silicon wafers instead of SOI. Compare T-RAM.

Z-transform

An operation to convert a discrete (sampled) time-domain system, modeled as a linear difference equation, into the frequency domain, where it’s just a weighted sum. For a stable system, all poles occur at values of z within the unit circle on the complex plane. If the value of z is restricted to lie on the unit circle, you have a Fourier transform. Compare Laplace transform.

Zulu

Refers to Zulu time, which is basically the same as UTC, or what used to be called Greenwich Mean Time (GMT).