Computers are switching networks {switching network}|, like telephone exchanges. CPUs are electronic switching devices, which keep current state until next machine step resets switches. Instructions, from registers, open and close switches that activate hardware.
Computers {analog computer}| can have electronic circuits that use electrical or physical magnitudes, rather than digital codes, to represent numbers and manipulate physical quantities algebraically, rather than digitally.
types
Analog computers {integrator computer} {summing integrator} can calculate integrals. Differential analyzers find slope or gradient. Analog computers can sense coincidences, sense anti-coincidences, combine pulses, amplify {summing amplifier}, time, shape, invert pulses {inverter}, invert and amplify {inverter amplifier}, find voltages {coefficient potentiometer}, supply constant voltage {constant-voltage supply}, and amplify selectively {operational amplifier}.
DNA can code combinations {DNA computer}. Filters can look for answer pieces. DNA hybridization indicates solution. DNA performs faster than computers.
Large computers {server, computer} can receive input from many smaller computers {client}.
Bigger computers {mainframe computer}| are faster, have more memory, and have more input/output terminals.
Midsize computers {minicomputer}| can perform most mainframe-computer functions but slower and cheaper, with less memory and less input/output terminals.
Smaller computers {workstation}| can function independently and perform complex and fast calculations.
The smallest computers {microcomputer}| function independently and perform most functions.
Computer systems have physical parts {computer, parts} {peripheral}. CPU reads instructions and data and calculates. Memory stores data and instructions. Input receives data. Output prints, displays, or sends data to another device.
relations
Input or output devices connect to peripheral-control bus, which connects to input-output processor, which connects to CPU and memory. Central processor connects to input-output processor and memory. Memory connects to input-output processor and CPU.
computer clock
Computer clocks send electric pulse at beginning of CPU cycles or steps. Time pulse into AND-circuit flip-flop sets flip-flop circuit. Time-pulse length must be long enough to set flip-flop. Signals go from one flip-flop circuit to the next in one time pulse. Time interval between CPU clock pulses must be long enough to let signal stabilize and to let pulse pass through longest network.
data protection
Duplicate equipment can preserve data. Comparing twin equipment can check for errors. Duplicate equipment can share work. One can switch on as backup, if other fails. Backup methods {failsoft} can limit data loss from failures. Central-control unit can switch off parts that have failed or are being serviced {controlled reconfiguration}.
Computers have a control part {central processing unit}| {central processor} (CPU).
functions
CPUs route signals, control input and output, and decode and execute instructions.
modules
CPUs have hardware modules that receive one or two inputs, perform functions, and send results to memory or output. Modules count {counter circuit}, add {adder circuit}, make one signal from many signals {decoder}, make several inputs into code {encoder}, or make one code into another code {translator circuit}. Gates can perform logical functions. Comparator compares number or string values.
subtraction
Subtraction adds input-number 10s complement to first number, using adder circuits.
multiplication
Multiplying repeats adding and shifts register using adder circuit.
division
Division has carry detector and restoring method, using adder circuit.
CPUs and memories have locations {register, computer}| for holding input values, output values, instructions, results, and addresses. Registers {look-ahead register} can hold next instruction or input value. Registers {accumulator register} can hold processing result or point to memory location holding result. Registers {address register} can hold other-register locations. Registers {operation code register} can hold operation instructions. Registers {temporary storage register} can hold data to transfer to other registers. Registers {stack} can hold value sequences. Stacks {stack counter register} can hold word address.
Register series {multi-register} can have fixed addresses for registers. Register series {stack processor} can be in CPU memory, so operations use only pushdown and popup in stack, with no addresses.
transfer
Information can move in sequence from one register to another on one path {bit serial} {character serial}. Information can move on parallel paths simultaneously {bit parallel} {character parallel}.
Electrical circuits {differentiator}| can find difference between two inputs. Differentiators can have input voltage from ground through capacitance to output voltage node, which connects to ground using diode or resistor. RC-circuit time constant must be small.
Wires can connect device to ground {electron sink}| {electrical ground}, which can absorb any number of electrons.
Circuit currents come from batteries or other voltage sources {electron source}|.
Electrical circuits {flip-flop circuit}| can change output voltage from zero to unit voltage and from unit voltage to zero, after input. Flip-flop circuits can have two inputs, each from transistor ground to base. For both transistors, emitters connect to ground. For both transistors, collector connects to other-transistor base. Both transistors have grounded emitters. Second-transistor collector connects through resistance to output voltage node, which connects through capacitor to ground.
Electrical circuits {hold-on relay}| can maintain voltage until switch changes. Hold-on relays can have grounded inductor, which connects to two switches. First switch leads to third switch. Second switch leads to third switch but also connects to ground through capacitor. Output voltage is across third switch. Output voltage is 0 or 1 and does not change until one of first two switches changes. Hold-on relay in OR circuit has output voltage 1 if OR is true. Hold-on relay in AND circuit has output voltage 0 if AND is true.
Electrical circuits {integrator circuit}| can add two inputs. Integrators can have input voltage from ground through resistor to output voltage node, which connects through capacitor to ground. RC-circuit time constant must be large.
Electrical circuits {logic circuit}| {logic gate} can perform logical operations, such as AND, OR, NOT, NOT OR {NOR gate, circuit}, and NOT AND. For NAND gates, P|Q = NOT(P AND Q). For AND gates, if all inputs are 1, output is 1. For OR gates, if at least one input is 1, output is 1. For inverter gates, if input is 1, output is 0. NAND gates are AND, followed by inverter. NOR gates are OR, followed by inverter [Church, 1956].
Logic circuits {AND gate}| can be equivalent to (A v B) or (A and B). AND gates can have two input voltages, each from ground to reverse diode. Output currents combine at node whose output voltage is across resistor and capacitor, each of which is parallel to input diode. AND gates can have two input voltages, each from ground through resistor to transistor base, which also connects through resistor to ground. One emitter connects to ground, and other emitter connects to first-transistor collector. Output voltage is at second collector, which lies across resistor and capacitor to grounded emitter.
Logic circuits {AND/OR gate} {AND-OR gate}| can have two system inputs, controller input, and output. Output of 2 or 3 sends output. If controller is 0, circuit is AND gate. If controller is 1, circuit is OR gate.
Logic circuits {NEGATIVE AND gate}| {NAND gate} {Sheffer stroke} can be equivalent to ~(A v B) or not (A and B). NEGATIVE AND gates can have two input voltages, each from ground to diode, whose output currents combine at node whose output voltage is across resistor and capacitor to ground. NEGATIVE AND gates can have two input voltages, each from ground to reverse diode, whose output currents combine at node, which connects across resistor to ground and connects to diode. Diode output current goes to transistor base, which connects across resistor to ground. Emitter connects to ground. Output voltage is from collector to grounded emitter, across resistor.
Logic circuits {NEGATIVE OR gate}| {NOR gate, negative or} can be equivalent to ~(A ^ B) or not (A or B). NEGATIVE OR gates can have two input voltages, each from ground to reverse diode, whose output currents combine at node. Node connects across resistor to ground and leads to diode, whose output current goes to transistor base, which connects across resistor to ground. Emitter connects to ground. Output voltage is at collector, which connects across resistor to ground.
Logic circuits {NOT gate}| {inverter circuit} can be equivalent to ~A or not A. NOT gates can have input voltage from ground through resistor to transistor base, which lies across resistor and capacitor to ground. Emitter connects to ground. Output voltage is across capacitor to collector, which connects across diodes and resistors to ground.
Logic circuits {OR gate}| can be equivalent to (A ^ B) or (A OR B). OR gates can have two input voltages, each from ground to diode. Two output currents combine at node whose output voltage is across resistor to ground. OR gates can have two input voltages, each from ground to diode, whose output currents combine at transistor base. Base also connects through resistor and capacitor to ground. Emitter connects to ground. Output voltage is at collector, which connects across resistor and capacitor to grounded emitter.
Analog signal magnitude can convert to digital and then reconvert for display {compression-decompression} {code-decoder} {codec}, possibly using time-division multiplexing.
Sampling analog signal magnitude at regular intervals can code binary signals {pulse-code modulation} {analog-to-digital}, possibly using multiplexing {time-division multiplexing}.
Digital input can go through low-pass filter with frequency close to digital frequency {pulse-width modulation} {digital-to-analog}. Negative feedback in one-bit digital-to-analog converters {Digital to Analog Converter} (DAC) can create high-pass filter that eliminates noise {pulse-density modulation} {oversampling DAC}. Digital bits can have resistances across voltage or have current sources {binary weighted DAC} {R2R ladder DAC} {segmented DAC} {hybrid DAC}.
Input or output devices {memory, computer} store data on magnetic disk {tanking} or in semiconductor memory {scratch pad memory}. Memories have byte sets. Memory-control devices assign addresses to bytes and read, write, sense, or inhibit bits.
Temporary memories {cache, memory}| can hold data.
Memories {holographic memory} can use interference patterns to store information and coherent input to retrieve information.
At surface positions, current can change magnetized-bubble direction {magnetic bubble memory}.
Magnetic cores can be registers {magnetic core memory}. Wire circles carry current to make solenoids with magnetism. Wires through magnetic cores can turn current off or on. Other wires through magnetic cores can read whether magnetism is present or not.
Memory controllers can read or write disks {random-access memory} (RAM) at any register location at all times. System stores information at random locations. For strings, logically add bits to make unique random numbers. Place string in memory at random-number position. Add line to table {hash table} relating memory-location random numbers to strings. To recover string from memory, look up random number in table. At that location, retrieve string from memory. Logically subtract bits from string.
Tapes {serial memory} read and write in sequence.
Disk or tape magnetic films {thin-film memory} can magnetize or not at all positions.
Programs obtain data values or programming instructions {input, computer} by opening and reading files. Input devices include magnetic tape, magnetic disk, magnetic drum, card reader, microfilm, microfiche, keytape from typewriter to tape, paper-tape reader, mark-sense reader, optical character recognition {optical character recognition} (OCR), cathode ray terminal, data cells, magnetic card, diskette, floppy disk, and flash memory card.
Programs display, print, send data to other devices, or make data-value or programming-parameter files {output, computer}. Output devices include de-collator, burster, folder, line printer, laser printer, card puncher, paper tape puncher, key-to-disc, and key-to-drum.
File transfer protocol {file transfer protocol} (FTP) allows public file access via anonymous log on. There is a user account for anonymous logons (GUEST by default) and a default home directory.
CPUs can connect {channel} to one input or output device {fixed channel} or switch from one input or output device to another {floating channel}.
Input-output lines {line, input and output} {input line} {output line} connect CPU and device. Direct lines {bit stream} can connect one input or output device to CPU. Leased telephone lines and modems connect one input or output device to CPU. Multiple lines connect to switching network, which connects to CPU. CPU lines {multi-drop line} can have several modems, so CPU polls and selects data. CPU lines {line concentrator} can receive direct and telephone lines, poll them, and send bit-stream packets to CPU.
Computer devices {adapter} can make bits into line characters.
Computer devices {data communications controller} {datacom} can control data input and output from different terminals.
types
Datacoms {uniplexor} {single line control} (SLC) can take bits from one line and pass characters to CPU. Datacoms {multiplexor} {multi-line control} (MLC) can take bits from many lines, sort bits by logic, and send characters to CPU. Datacoms {front-end processor} (FEP) can take bits from several lines, assemble them into words, and send words to CPU. Datacoms {data communications processor} can take bits from one line, assemble them into words, add message header, queue messages, and send them to memory or input-output processor.
Devices {modem}| {data set} can convert digital bits to analog data, or vice versa, or alter line bit streams.
Devices {sort-merge} can manipulate input and output forms.
Robots {robot, computer} can recognize patterns [Aleksander, 1983] [Liang et al., 1997]. QRio android robot can move and converse.
Kismet is a robot head whose parts can move like human head parts [Breazeal, 2001]. If it is too close to see, it cranes back, and if it is too far, it cranes forward. It checks for movement, skin color, and saturated colors and looks in weighted direction. State depends on happiness, stimulation, and willingness for new stimuli. State affects where it looks. It checks pitch for approving, disapproving, attending, and soothing patterns, as used worldwide by mothers to babies, but it has no language ability. It can make sounds in pitch patterns. It can move eyebrows, lips, and ears to reflect happiness, stimulation, and willingness for new stimuli.
In neuromorphic systems {silicon retina}, photodetectors output voltages proportional to current logarithm. Resistive network locally weights averages, so point effects decrease exponentially with distance. Retinal output is difference between local and overall voltage [Mead and Mahowald, 1991].
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Date Modified: 2022.0225