Complementary metal–oxide–semiconductor (CMOS) is a major class of integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits. CMOS technology is also used for a wide variety of analog circuits such as image sensors, data converters, and highly integrated transceivers for many types of communication. Frank Wanlass successfully patented CMOS in 1967 (US Patent 3,356,858).
CMOS was also sometimes referred to as complementary-symmetry metal–oxide–semiconductor (or COS-MOS). The words "complementary-symmetry" refer to the fact that the typical digital design style with CMOS uses complementary and symmetrical pairs of p-type and n-type metal oxide semiconductor field effect transistors (MOSFETs) for logic functions.
Two important characteristics of CMOS devices are high noise immunity and low static power consumption. Significant power is only drawn when the transistors in the CMOS device are switching between on and off states. Consequently, CMOS devices do not produce as much waste heat as other forms of logic, for example transistor-transistor logic (TTL) or NMOS logic, which uses all n-channel devices without p-channel devices. CMOS also allows a high density of logic functions on a chip.
The phrase "metal–oxide–semiconductor" is a reference to the physical structure of certain field-effect transistors, having a metal gate electrode placed on top of an oxide insulator, which in turn is on top of a semiconductor material. Aluminum was once used but now the material is polysilicon. Other metal gates have made a comeback with the advent of high-k dielectric materials in the CMOS process, as announced by IBM and Intel for the 45 nanometer node and beyond.
"CMOS" refers to both a particular style of digital circuitry design, and the family of processes used to implement that circuitry on integrated circuits (chips). CMOS circuitry dissipates less power when static, and is denser than other implementations having the same functionality. As this advantage has grown and become more important, CMOS processes and variants have come to dominate, so that the vast majority of modern integrated circuit manufacturing is on CMOS processes.[citation needed]
CMOS circuits use a combination of p-type and n-type metal–oxide–semiconductor field-effect transistors (MOSFETs) to implement logic gates and other digital circuits found in computers, telecommunications equipment, and signal processing equipment. Although CMOS logic can be implemented with discrete devices (for instance, in an introductory circuits class), typical commercial CMOS products are integrated circuits composed of millions (or hundreds of millions) of transistors of both types on a rectangular piece of silicon of between 0.1 and 4 square centimeters.These devices are commonly called "chips", although within the industry they are also referred to as "die" (singular) or "dice", "dies", or "die" (plural).
In computing, BIOS is an acronym that stands for Basic Input/Output System, or in some cases, Built In Operating System.BIOS refers, in part, to the firmware code (a type of boot loader) run by a PC when first powered on. The primary function of the BIOS is to identify and initialize system component hardware such as the video display card, hard disk, and floppy disk and some other hardware devices. This is to prepare the machine into a known low capability state, so other software programs stored on various media can be loaded, executed, and given control of the PC.This process is known as booting, or booting up, which is short for bootstrapping.
The BIOSes of IBM PC class machines are coded programs embedded on a chip that recognize and control various devices that make up x86 personal computers, and provide a small library of basic Input/Output functions that can be called to operate and control the peripherals such as the keyboard, text display functions and so forth.
Computers designed to run Windows ME or Windows 2000, or later, supersede this basic monitor functionality by taking over direct control of the interrupt table and replacing the monitor routines with faster and more robust low-level modules that, unlike the BIOS function set, are re-entrant. Various BIOS functions in ROM were left in control in earlier Windows versions, and the BIOS only comes into play today in the alternate shell Cmd.exe, or if the machine is booted into a legacy DOS version.
The term first appeared in the CP/M operating system, describing the part of CP/M loaded during boot time that interfaced directly with the hardware (CP/M machines usually had a simple boot loader in ROM, and nothing else). Most versions of DOS have a file called "IBMBIO.COM" or "IO.SYS" that is analogous to the CP/M disk BIOS. The term was also known as Binary Input/Output System and Basic Integrated Operating System.
Among other classes of computers, the generic terms boot monitor, boot loader or boot ROM we