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.
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.
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.
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.
The earliest known method of memory storage and subsequent computerized reading is the Antikythera mechanism (c. 100–150 BCE) which utilizes over thirty gears that spin a dial indicator.