In computer engineering, a logic family is one of two related concepts: A logic family of monolithic digital integrated circuit devices is a group of electronic logic gates constructed using one of several different designs, usually with compatible logic levels and power supply characteristics within a family. Many logic families were produced as individual components, each containing one or a few related basic logical functions, which could be used as "building-blocks" to create systems or as so-called "glue" to interconnect more complex integrated circuits. A logic family may also be a set of techniques used to implement logic within VLSI integrated circuits such as central processors, memories, or other complex functions. Some such logic families use static techniques to minimize design complexity. Other such logic families, such as domino logic, use clocked dynamic techniques to minimize size, power consumption and delay. Before the widespread use of integrated circuits, various solid-state and vacuum-tube logic systems were used but these were never as standardized and interoperable as the integrated-circuit devices. The most common logic family in modern semiconductor devices is metal–oxide–semiconductor (MOS) logic, due to low power consumption, small transistor sizes, and high transistor density. Technologies The list of packaged building-block logic families can be divided into categories, listed here in roughly chronological order of introduction, along with their usual abbreviations: Resistor–transistor logic (RTL) Direct-coupled transistor logic (DCTL) Direct-coupled unipolar transistor logic (DCUTL) Resistor–capacitor–transistor logic (RCTL) Emitter-coupled logic (ECL) Positive emitter-coupled logic (PECL) Low-voltage PECL (LVPECL) Complementary transistor micrologic (CTuL) Diode–transistor logic (DTL) Complemented transistor diode logic (CTDL) High-threshold logic (HTL) Transistor–transistor logic (TTL) Metal–oxide–semiconductor (MOS) logic P-type MOS (PMOS) logic N-type MOS (NMOS) logic Depletion-load NMOS logic High-density NMOS (HMOS) Complementary MOS (CMOS) logic Bipolar MOS (BiMOS) logic Bipolar CMOS (BiCMOS) Integrated injection logic (I2L) Gunning transceiver logic (GTL) The families (RTL, DTL, and ECL) were derived from the logic circuits used in early computers, originally implemented using discrete components. One example is the Philips NORBIT family of logic building blocks. The PMOS and I2L logic families were used for relatively short periods, mostly in special purpose custom large-scale integration circuits devices and are generally considered obsolete. For example, early digital clocks or electronic calculators may have used one or more PMOS devices to provide most of the logic for the finished product. The F14 CADC, Intel 4004, Intel 4040, and Intel 8008 microprocessors and their support chips were PMOS. Of