Reading is an action performed by computers, to acquire data from a source and place it into their volatile memory for processing. Computers may read information from a variety of sources, such as magnetic storage, the Internet, or audio and video input ports. Reading is one of the core functions of a Turing machine. A read cycle is the act of reading one unit of information (e.g. a byte). A read channel is an electrical circuit that transforms the physical magnetic flux changes into abstract bits. A read error occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive. Example For example, a computer may read information off a floppy disk and store it temporarily in random-access memory before it is written to the hard drive to be processed at a future date. Memory types CMOS Complementary metal–oxide–semiconductor (CMOS) is a non-volatile medium. It is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits. Memory is read through the use of a combination of p-type and n-type metal–oxide–semiconductor field-effect transistors (MOSFETs). In CMOS logic, a collection of n-type MOSFETs are arranged in a pull-down network between the output node and the lower-voltage power supply rail, named Vss, which often has ground potential. By asserting or de-asserting the inputs to the CMOS circuit, individual transistors along the pull-up and pull-down networks become conductive and resistive to electric current, and results in the desired path connecting from the output node to one of the voltage rails. Flash Flash memory stores information in an array of memory cells made from floating-gate transistors. Flash memory utilizes either NOR logic or NAND logic. In NOR gate flash, each cell resembles a standard MOSFET, except the transistor has two gates instead of one. On top is the control gate (CG), as in other MOS transistors, but below this, there is a floating gate (FG) insulated all around by an oxide layer. The FG is interposed between the CG and the MOSFET channel, and because the FG is electrically isolated by its insulating layer, any electrons placed on it are trapped there and, under normal conditions, will not discharge for many years. When current flow through the MOSFET channel binary code is generated, reproducing the stored data. NAND gate flash utilizes tunnel injection for writing and tunnel release for erasing. NAND flash memory forms the