Computers input, process, and output information
Richard K. Herz, ReactorLab.net
Input
Examples of input devices include keyboards, touch screens, joy sticks, cameras, microphones, strain
gauges, photocells, credit card chip readers.
A sensor responds to information from the environment (light, pressure, chemical) to produce a signal
of some type, often an electrical current or voltage. A transducer is a device that can convert one type
of signal into another. A digital input/output (I/O) device converts a signal to binary numbers. An
analog-to-digital (A/D) converter converts an electrical voltage or current into binary numbers.
Encoding of input information
All information that comes into a digital computer must be converted to numbers in the binary number
system. This is because all communication and processing in digital computers and digital
communication systems uses binary numbers, for reasons explained below.
Alphanumeric characters are converted to binary numbers via the process of a table of conversions.
Conversion table systems include ASCII and several varieties of Unicode. For example, "A" is first
converted in ASCII to the decimal number 65 and then to the binary equivalent of 65, which is
01000001. Bits are added to denote that the value is a character value. ("a" is 97)
Sound is converted to a continuous electrical voltage signal in a microphone. Then the continuous
signal is periodically "sampled" by converting the signal value to a binary number in an analog-to-
digital converter. This results is a series of binary numbers, each representing a signal value separated
by a known time interval.
Images can be segmented into a grid of picture elements called pixels. The color values and intensity of
each pixel can be stored as numbers in 2D arrays. These values are converted to binary numbers.
Processing of information - hardware
A digital computer or a digital communication system is built out of nanometer sized physical devices,
each of which can be in one of two, binary states. Each binary state is called a bit. The states of a
collection of devices - a collection of bits called a byte - can represent the binary equivalent of a
decimal number.
Examples of physical data storage devices include transistors in integrated circuits (on-off), capacitors
(charged-discharged), field orientation of magnetic elements in hard disks (N-S), and optical
reflectivity of organic dies or aluminum films in DVDs (specular-diffuse).
There are several reasons that digital computers process digital information. These reasons include:
•high density of information
◦binary-state devices can be simple and made very small
Richard K. Herz, ReactorLab.net, p. 1 of 3
