Reading (technical)
Encyclopedia
Reading is an action performed by computers, to acquire data
from a source and place it into their volatile memory
for processing
. For example, a computer may read information off a floppy disk
and store it in random access memory to be placed on the hard drive to be processed at a future date. Computers may read information from a variety of sources, such as magnetic storage
, the Internet
, or audio
and video
input ports
.
The act of reading one unit of information (e.g. a byte) is sometimes called a read cycle.
The electrical circuit that transforms the physical magnetic flux changes into abstract bits is called the read channel. A read error occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive.
Reading can be abstracted to one of the main functions of a Turing machine
.
. It is used in microprocessor
s, microcontroller
s, 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 transistor
s (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 resitive
to electrical current, and results in the desired path connecting from the output node to one of the voltage rails.
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 electron
s 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 core of the removable USB
storage devices known as USB flash drive
s, as well as most memory card
formats available today.
in a magnetizable material to store data and is a form of non-volatile memory
. Magnetic storage media can be classified as either sequential access memory
or random access memory although in some cases the distinction is not perfectly clear.
Small polarized ferrous cores in the shape of wires or poles are flipped along the surface of reading and writing into the desired data is stored. Accessing different parts of the medium involves winding the wire forward or backward until the point of interest is found. Data is read through a small reading peripheral which amplifies which side the ferrous cores are arranged.
(c. 100–150 BCE
) which utilizes over thirty gears that spin a dial indicator. Following the Antikythera mechanism, Hero of Alexandria
(c. 10–70 CE
) designed a spinning wheel with pegs, when the pegs are reach the wheel in turn reverses the direction of spin. It was used to raise, lower, and moves displays for amphitheatre shows.
Punched cards became popularized from 1900 to 1950 as it became the most common storage medium for computers. The information was read through a method of identifying the holes in the card which was then converted to another medium.
or multiplexer.
flat, circular, usually polycarbonate disks. Data is stored in pits or bumps arranged in sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. Data read by a means of a laser; when the laser enters a pit, the focus of the laser is changed and interpenetrated by the reader's software.
Reading is an action performed by computers, to acquire data
from a source and place it into their volatile memory
for processing
. For example, a computer may read information off a floppy disk
and store it in random access memory to be placed on the hard drive to be processed at a future date. Computers may read information from a variety of sources, such as magnetic storage
, the Internet
, or audio
and video
input ports
.
The act of reading one unit of information (e.g. a byte) is sometimes called a read cycle.
The electrical circuit that transforms the physical magnetic flux changes into abstract bits is called the read channel. A read error occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive.
Reading can be abstracted to one of the main functions of a Turing machine
.
. It is used in microprocessor
s, microcontroller
s, 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 transistor
s (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 resitive
to electrical current, and results in the desired path connecting from the output node to one of the voltage rails.
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 electron
s 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 core of the removable USB
storage devices known as USB flash drive
s, as well as most memory card
formats available today.
in a magnetizable material to store data and is a form of non-volatile memory
. Magnetic storage media can be classified as either sequential access memory
or random access memory although in some cases the distinction is not perfectly clear.
Small polarized ferrous cores in the shape of wires or poles are flipped along the surface of reading and writing into the desired data is stored. Accessing different parts of the medium involves winding the wire forward or backward until the point of interest is found. Data is read through a small reading peripheral which amplifies which side the ferrous cores are arranged.
(c. 100–150 BCE
) which utilizes over thirty gears that spin a dial indicator. Following the Antikythera mechanism, Hero of Alexandria
(c. 10–70 CE
) designed a spinning wheel with pegs, when the pegs are reach the wheel in turn reverses the direction of spin. It was used to raise, lower, and moves displays for amphitheatre shows.
Punched cards became popularized from 1900 to 1950 as it became the most common storage medium for computers. The information was read through a method of identifying the holes in the card which was then converted to another medium.
or multiplexer.
flat, circular, usually polycarbonate disks. Data is stored in pits or bumps arranged in sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. Data read by a means of a laser; when the laser enters a pit, the focus of the laser is changed and interpenetrated by the reader's software.
Reading is an action performed by computers, to acquire data
from a source and place it into their volatile memory
for processing
. For example, a computer may read information off a floppy disk
and store it in random access memory to be placed on the hard drive to be processed at a future date. Computers may read information from a variety of sources, such as magnetic storage
, the Internet
, or audio
and video
input ports
.
The act of reading one unit of information (e.g. a byte) is sometimes called a read cycle.
The electrical circuit that transforms the physical magnetic flux changes into abstract bits is called the read channel. A read error occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive.
Reading can be abstracted to one of the main functions of a Turing machine
.
. It is used in microprocessor
s, microcontroller
s, 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 transistor
s (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 resitive
to electrical current, and results in the desired path connecting from the output node to one of the voltage rails.
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 electron
s 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 core of the removable USB
storage devices known as USB flash drive
s, as well as most memory card
formats available today.
in a magnetizable material to store data and is a form of non-volatile memory
. Magnetic storage media can be classified as either sequential access memory
or random access memory although in some cases the distinction is not perfectly clear.
Small polarized ferrous cores in the shape of wires or poles are flipped along the surface of reading and writing into the desired data is stored. Accessing different parts of the medium involves winding the wire forward or backward until the point of interest is found. Data is read through a small reading peripheral which amplifies which side the ferrous cores are arranged.
(c. 100–150 BCE
) which utilizes over thirty gears that spin a dial indicator. Following the Antikythera mechanism, Hero of Alexandria
(c. 10–70 CE
) designed a spinning wheel with pegs, when the pegs are reach the wheel in turn reverses the direction of spin. It was used to raise, lower, and moves displays for amphitheatre shows.
Punched cards became popularized from 1900 to 1950 as it became the most common storage medium for computers. The information was read through a method of identifying the holes in the card which was then converted to another medium.
or multiplexer.
flat, circular, usually polycarbonate disks. Data is stored in pits or bumps arranged in sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. Data read by a means of a laser; when the laser enters a pit, the focus of the laser is changed and interpenetrated by the reader's software.
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
from a source and place it into their volatile memory
Volatile memory
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply...
for processing
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
. For example, a computer may read information off a floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
and store it in random access memory to be placed on the hard drive to be processed at a future date. Computers may read information from a variety of sources, such as magnetic storage
Magnetic storage
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using...
, the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
, or audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
and video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
input ports
Computer port (hardware)
In computer hardware, a port serves as an interface between the computer and other computers or peripheral devices. Physically, a port is a specialized outlet on a piece of equipment to which a plug or cable connects...
.
The act of reading one unit of information (e.g. a byte) is sometimes called a read cycle.
The electrical circuit that transforms the physical magnetic flux changes into abstract bits is called the read channel. A read error occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive.
Reading can be abstracted to one of the main functions of a Turing machine
Turing machine
A Turing machine is a theoretical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a...
.
CMOS
Complementary metal–oxide–semiconductor (CMOS) is a non-volatile mediumNon-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
. It is used in microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
s, microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
s, static RAM
Static random access memory
Static random-access memory is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM , it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit...
, 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 transistor
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
s (MOSFETs). In CMOS logic, a collection of n-type MOSFETs are arranged in a pull-down
Pull-up resistor
Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels if external devices are disconnected or high-impedance...
network
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
between the output node
Node (circuits)
In electrical engineering, node refers to any point on a circuit where two or more circuit elements meet. For two nodes to be different, their voltages must be different. Without any further knowledge, it is easy to establish how to find a node by using Ohm's Law: V=IR. When looking at circuit...
and the lower-voltage power supply rail
Voltage source
In electric circuit theory, an ideal voltage source is a circuit element where the voltage across it is independent of the current through it. A voltage source is the dual of a current source. In analysis, a voltage source supplies a constant DC or AC potential between its terminals for any current...
, named Vss
IC power supply pin
Almost all integrated circuits have at least two pins that connect to the power rails of the circuit in which they are installed. These are known as the IC's power supply pins...
, which often has ground
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
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 resitive
Resistivity
Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. The SI unit of electrical resistivity is the ohm metre...
to electrical 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 is utilizes either NOR logic or NAND logic.In NOR gate
NOR gate
The NOR gate is a digital logic gate that implements logical NOR - it behaves according to the truth table to the right. A HIGH output results if both the inputs to the gate are LOW . If one or both input is HIGH , a LOW output results. NOR is the result of the negation of the OR operator...
flash, each cell resembles a standard MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
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
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
layer. The FG is interposed between the CG and the MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
channel, and because the FG is electrically isolated by its insulating layer, any electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s 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
Binary code
A binary code is a way of representing text or computer processor instructions by the use of the binary number system's two-binary digits 0 and 1. This is accomplished by assigning a bit string to each particular symbol or instruction...
is generated, reproducing the stored data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
.
NAND gate flash utilizes tunnel injection
Tunnel injection
Tunnel injection is the quantum tunneling effect, also called Fowler-Nordheim tunnel injection, when charge carriers are injected to an electric conductor through a thin layer of an electric insulator....
for writing and tunnel release for erasing. NAND flash memory forms the core of the removable USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
storage devices known as USB flash drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...
s, as well as most memory card
Memory card
A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles...
formats available today.
Magnetic
The magnetic medium is found in magnetic tape, hard disk drives, floppy disks, and so on. This medium uses different patterns of magnetizationMagnetization
In classical electromagnetism, magnetization or magnetic polarization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material...
in a magnetizable material to store data and is a form of non-volatile memory
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
. Magnetic storage media can be classified as either sequential access memory
Sequential access memory
In computing, sequential access memory is a class of data storage devices that read their data in sequence. This is in contrast to random access memory where data can be accessed in any order...
or random access memory although in some cases the distinction is not perfectly clear.
Small polarized ferrous cores in the shape of wires or poles are flipped along the surface of reading and writing into the desired data is stored. Accessing different parts of the medium involves winding the wire forward or backward until the point of interest is found. Data is read through a small reading peripheral which amplifies which side the ferrous cores are arranged.
Mechanical
The mechanical medium utilizes one of the oldest methods of computing and has largely become obsolete. The earliest known method of memory storage and subsequent computerized reading is the Antikythera mechanismAntikythera mechanism
The Antikythera mechanism is an ancient mechanical computer designed to calculate astronomical positions. It was recovered in 1900–1901 from the Antikythera wreck. Its significance and complexity were not understood until decades later. Its time of construction is now estimated between 150 and 100...
(c. 100–150 BCE
Common Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...
) which utilizes over thirty gears that spin a dial indicator. Following the Antikythera mechanism, Hero of Alexandria
Hero of Alexandria
Hero of Alexandria was an ancient Greek mathematician and engineerEnc. Britannica 2007, "Heron of Alexandria" who was active in his native city of Alexandria, Roman Egypt...
(c. 10–70 CE
Common Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...
) designed a spinning wheel with pegs, when the pegs are reach the wheel in turn reverses the direction of spin. It was used to raise, lower, and moves displays for amphitheatre shows.
Punched cards became popularized from 1900 to 1950 as it became the most common storage medium for computers. The information was read through a method of identifying the holes in the card which was then converted to another medium.
Peripherals
The usage of electronic computer peripherals became popularized as means of linking two computing devices. Information is sent in electronic singles which are interpreted by a MultiplexerMultiplexer
In electronics, a multiplexer is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output...
or multiplexer.
Optical disks
Optical disks refer to the non-volatileNon-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
flat, circular, usually polycarbonate disks. Data is stored in pits or bumps arranged in sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. Data read by a means of a laser; when the laser enters a pit, the focus of the laser is changed and interpenetrated by the reader's software.
See also
- X (writing speed)X (writing speed)Original CD-ROM drives could read data at 150 kibibytes per second. As faster drives were released, the write speeds and read speeds for optical discs came to be indicated by manufacturers in terms of a multiple of the speed of the drives originally released to market. Using the notation nX, n is...
- Computer storageComputer storageComputer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
- Turing machineTuring machineA Turing machine is a theoretical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a...
- Optical character recognitionOptical character recognitionOptical character recognition, usually abbreviated to OCR, is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping...
Reading is an action performed by computers, to acquire data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
from a source and place it into their volatile memory
Volatile memory
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply...
for processing
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
. For example, a computer may read information off a floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
and store it in random access memory to be placed on the hard drive to be processed at a future date. Computers may read information from a variety of sources, such as magnetic storage
Magnetic storage
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using...
, the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
, or audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
and video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
input ports
Computer port (hardware)
In computer hardware, a port serves as an interface between the computer and other computers or peripheral devices. Physically, a port is a specialized outlet on a piece of equipment to which a plug or cable connects...
.
The act of reading one unit of information (e.g. a byte) is sometimes called a read cycle.
The electrical circuit that transforms the physical magnetic flux changes into abstract bits is called the read channel. A read error occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive.
Reading can be abstracted to one of the main functions of a Turing machine
Turing machine
A Turing machine is a theoretical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a...
.
CMOS
Complementary metal–oxide–semiconductor (CMOS) is a non-volatile mediumNon-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
. It is used in microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
s, microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
s, static RAM
Static random access memory
Static random-access memory is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM , it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit...
, 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 transistor
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
s (MOSFETs). In CMOS logic, a collection of n-type MOSFETs are arranged in a pull-down
Pull-up resistor
Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels if external devices are disconnected or high-impedance...
network
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
between the output node
Node (circuits)
In electrical engineering, node refers to any point on a circuit where two or more circuit elements meet. For two nodes to be different, their voltages must be different. Without any further knowledge, it is easy to establish how to find a node by using Ohm's Law: V=IR. When looking at circuit...
and the lower-voltage power supply rail
Voltage source
In electric circuit theory, an ideal voltage source is a circuit element where the voltage across it is independent of the current through it. A voltage source is the dual of a current source. In analysis, a voltage source supplies a constant DC or AC potential between its terminals for any current...
, named Vss
IC power supply pin
Almost all integrated circuits have at least two pins that connect to the power rails of the circuit in which they are installed. These are known as the IC's power supply pins...
, which often has ground
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
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 resitive
Resistivity
Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. The SI unit of electrical resistivity is the ohm metre...
to electrical 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 is utilizes either NOR logic or NAND logic.In NOR gate
NOR gate
The NOR gate is a digital logic gate that implements logical NOR - it behaves according to the truth table to the right. A HIGH output results if both the inputs to the gate are LOW . If one or both input is HIGH , a LOW output results. NOR is the result of the negation of the OR operator...
flash, each cell resembles a standard MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
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
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
layer. The FG is interposed between the CG and the MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
channel, and because the FG is electrically isolated by its insulating layer, any electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s 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
Binary code
A binary code is a way of representing text or computer processor instructions by the use of the binary number system's two-binary digits 0 and 1. This is accomplished by assigning a bit string to each particular symbol or instruction...
is generated, reproducing the stored data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
.
NAND gate flash utilizes tunnel injection
Tunnel injection
Tunnel injection is the quantum tunneling effect, also called Fowler-Nordheim tunnel injection, when charge carriers are injected to an electric conductor through a thin layer of an electric insulator....
for writing and tunnel release for erasing. NAND flash memory forms the core of the removable USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
storage devices known as USB flash drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...
s, as well as most memory card
Memory card
A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles...
formats available today.
Magnetic
The magnetic medium is found in magnetic tape, hard disk drives, floppy disks, and so on. This medium uses different patterns of magnetizationMagnetization
In classical electromagnetism, magnetization or magnetic polarization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material...
in a magnetizable material to store data and is a form of non-volatile memory
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
. Magnetic storage media can be classified as either sequential access memory
Sequential access memory
In computing, sequential access memory is a class of data storage devices that read their data in sequence. This is in contrast to random access memory where data can be accessed in any order...
or random access memory although in some cases the distinction is not perfectly clear.
Small polarized ferrous cores in the shape of wires or poles are flipped along the surface of reading and writing into the desired data is stored. Accessing different parts of the medium involves winding the wire forward or backward until the point of interest is found. Data is read through a small reading peripheral which amplifies which side the ferrous cores are arranged.
Mechanical
The mechanical medium utilizes one of the oldest methods of computing and has largely become obsolete. The earliest known method of memory storage and subsequent computerized reading is the Antikythera mechanismAntikythera mechanism
The Antikythera mechanism is an ancient mechanical computer designed to calculate astronomical positions. It was recovered in 1900–1901 from the Antikythera wreck. Its significance and complexity were not understood until decades later. Its time of construction is now estimated between 150 and 100...
(c. 100–150 BCE
Common Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...
) which utilizes over thirty gears that spin a dial indicator. Following the Antikythera mechanism, Hero of Alexandria
Hero of Alexandria
Hero of Alexandria was an ancient Greek mathematician and engineerEnc. Britannica 2007, "Heron of Alexandria" who was active in his native city of Alexandria, Roman Egypt...
(c. 10–70 CE
Common Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...
) designed a spinning wheel with pegs, when the pegs are reach the wheel in turn reverses the direction of spin. It was used to raise, lower, and moves displays for amphitheatre shows.
Punched cards became popularized from 1900 to 1950 as it became the most common storage medium for computers. The information was read through a method of identifying the holes in the card which was then converted to another medium.
Peripherals
The usage of electronic computer peripherals became popularized as means of linking two computing devices. Information is sent in electronic singles which are interpreted by a MultiplexerMultiplexer
In electronics, a multiplexer is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output...
or multiplexer.
Optical disks
Optical disks refer to the non-volatileNon-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
flat, circular, usually polycarbonate disks. Data is stored in pits or bumps arranged in sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. Data read by a means of a laser; when the laser enters a pit, the focus of the laser is changed and interpenetrated by the reader's software.
See also
- X (writing speed)X (writing speed)Original CD-ROM drives could read data at 150 kibibytes per second. As faster drives were released, the write speeds and read speeds for optical discs came to be indicated by manufacturers in terms of a multiple of the speed of the drives originally released to market. Using the notation nX, n is...
- Computer storageComputer storageComputer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
- Turing machineTuring machineA Turing machine is a theoretical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a...
- Optical character recognitionOptical character recognitionOptical character recognition, usually abbreviated to OCR, is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping...
Reading is an action performed by computers, to acquire data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
from a source and place it into their volatile memory
Volatile memory
Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, unlike non-volatile memory which does not require a maintained power supply...
for processing
Process (computing)
In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...
. For example, a computer may read information off a floppy disk
Floppy disk
A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles...
and store it in random access memory to be placed on the hard drive to be processed at a future date. Computers may read information from a variety of sources, such as magnetic storage
Magnetic storage
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using...
, the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
, or audio
Sound
Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
and video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
input ports
Computer port (hardware)
In computer hardware, a port serves as an interface between the computer and other computers or peripheral devices. Physically, a port is a specialized outlet on a piece of equipment to which a plug or cable connects...
.
The act of reading one unit of information (e.g. a byte) is sometimes called a read cycle.
The electrical circuit that transforms the physical magnetic flux changes into abstract bits is called the read channel. A read error occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive.
Reading can be abstracted to one of the main functions of a Turing machine
Turing machine
A Turing machine is a theoretical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a...
.
CMOS
Complementary metal–oxide–semiconductor (CMOS) is a non-volatile mediumNon-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
. It is used in microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...
s, microcontroller
Microcontroller
A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...
s, static RAM
Static random access memory
Static random-access memory is a type of semiconductor memory where the word static indicates that, unlike dynamic RAM , it does not need to be periodically refreshed, as SRAM uses bistable latching circuitry to store each bit...
, 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 transistor
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
s (MOSFETs). In CMOS logic, a collection of n-type MOSFETs are arranged in a pull-down
Pull-up resistor
Pull-up resistors are used in electronic logic circuits to ensure that inputs to logic systems settle at expected logic levels if external devices are disconnected or high-impedance...
network
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
between the output node
Node (circuits)
In electrical engineering, node refers to any point on a circuit where two or more circuit elements meet. For two nodes to be different, their voltages must be different. Without any further knowledge, it is easy to establish how to find a node by using Ohm's Law: V=IR. When looking at circuit...
and the lower-voltage power supply rail
Voltage source
In electric circuit theory, an ideal voltage source is a circuit element where the voltage across it is independent of the current through it. A voltage source is the dual of a current source. In analysis, a voltage source supplies a constant DC or AC potential between its terminals for any current...
, named Vss
IC power supply pin
Almost all integrated circuits have at least two pins that connect to the power rails of the circuit in which they are installed. These are known as the IC's power supply pins...
, which often has ground
Ground (electricity)
In electrical engineering, ground or earth may be the reference point in an electrical circuit from which other voltages are measured, or a common return path for electric current, or a direct physical connection to the Earth....
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 resitive
Resistivity
Electrical resistivity is a measure of how strongly a material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. The SI unit of electrical resistivity is the ohm metre...
to electrical 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 is utilizes either NOR logic or NAND logic.In NOR gate
NOR gate
The NOR gate is a digital logic gate that implements logical NOR - it behaves according to the truth table to the right. A HIGH output results if both the inputs to the gate are LOW . If one or both input is HIGH , a LOW output results. NOR is the result of the negation of the OR operator...
flash, each cell resembles a standard MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
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
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
layer. The FG is interposed between the CG and the MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
channel, and because the FG is electrically isolated by its insulating layer, any electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s 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
Binary code
A binary code is a way of representing text or computer processor instructions by the use of the binary number system's two-binary digits 0 and 1. This is accomplished by assigning a bit string to each particular symbol or instruction...
is generated, reproducing the stored data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
.
NAND gate flash utilizes tunnel injection
Tunnel injection
Tunnel injection is the quantum tunneling effect, also called Fowler-Nordheim tunnel injection, when charge carriers are injected to an electric conductor through a thin layer of an electric insulator....
for writing and tunnel release for erasing. NAND flash memory forms the core of the removable USB
Universal Serial Bus
USB is an industry standard developed in the mid-1990s that defines the cables, connectors and protocols used in a bus for connection, communication and power supply between computers and electronic devices....
storage devices known as USB flash drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...
s, as well as most memory card
Memory card
A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles...
formats available today.
Magnetic
The magnetic medium is found in magnetic tape, hard disk drives, floppy disks, and so on. This medium uses different patterns of magnetizationMagnetization
In classical electromagnetism, magnetization or magnetic polarization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material...
in a magnetizable material to store data and is a form of non-volatile memory
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
. Magnetic storage media can be classified as either sequential access memory
Sequential access memory
In computing, sequential access memory is a class of data storage devices that read their data in sequence. This is in contrast to random access memory where data can be accessed in any order...
or random access memory although in some cases the distinction is not perfectly clear.
Small polarized ferrous cores in the shape of wires or poles are flipped along the surface of reading and writing into the desired data is stored. Accessing different parts of the medium involves winding the wire forward or backward until the point of interest is found. Data is read through a small reading peripheral which amplifies which side the ferrous cores are arranged.
Mechanical
The mechanical medium utilizes one of the oldest methods of computing and has largely become obsolete. The earliest known method of memory storage and subsequent computerized reading is the Antikythera mechanismAntikythera mechanism
The Antikythera mechanism is an ancient mechanical computer designed to calculate astronomical positions. It was recovered in 1900–1901 from the Antikythera wreck. Its significance and complexity were not understood until decades later. Its time of construction is now estimated between 150 and 100...
(c. 100–150 BCE
Common Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...
) which utilizes over thirty gears that spin a dial indicator. Following the Antikythera mechanism, Hero of Alexandria
Hero of Alexandria
Hero of Alexandria was an ancient Greek mathematician and engineerEnc. Britannica 2007, "Heron of Alexandria" who was active in his native city of Alexandria, Roman Egypt...
(c. 10–70 CE
Common Era
Common Era ,abbreviated as CE, is an alternative designation for the calendar era originally introduced by Dionysius Exiguus in the 6th century, traditionally identified with Anno Domini .Dates before the year 1 CE are indicated by the usage of BCE, short for Before the Common Era Common Era...
) designed a spinning wheel with pegs, when the pegs are reach the wheel in turn reverses the direction of spin. It was used to raise, lower, and moves displays for amphitheatre shows.
Punched cards became popularized from 1900 to 1950 as it became the most common storage medium for computers. The information was read through a method of identifying the holes in the card which was then converted to another medium.
Peripherals
The usage of electronic computer peripherals became popularized as means of linking two computing devices. Information is sent in electronic singles which are interpreted by a MultiplexerMultiplexer
In electronics, a multiplexer is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output...
or multiplexer.
Optical disks
Optical disks refer to the non-volatileNon-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
flat, circular, usually polycarbonate disks. Data is stored in pits or bumps arranged in sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. Data read by a means of a laser; when the laser enters a pit, the focus of the laser is changed and interpenetrated by the reader's software.
See also
- X (writing speed)X (writing speed)Original CD-ROM drives could read data at 150 kibibytes per second. As faster drives were released, the write speeds and read speeds for optical discs came to be indicated by manufacturers in terms of a multiple of the speed of the drives originally released to market. Using the notation nX, n is...
- Computer storageComputer storageComputer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
- Turing machineTuring machineA Turing machine is a theoretical device that manipulates symbols on a strip of tape according to a table of rules. Despite its simplicity, a Turing machine can be adapted to simulate the logic of any computer algorithm, and is particularly useful in explaining the functions of a CPU inside a...
- Optical character recognitionOptical character recognitionOptical character recognition, usually abbreviated to OCR, is the mechanical or electronic translation of scanned images of handwritten, typewritten or printed text into machine-encoded text. It is widely used to convert books and documents into electronic files, to computerize a record-keeping...