Calculators {calculator}| {electronic calculator} can be for adding, subtracting, multiplying, dividing, and other algorithms. Electronic calculators store binary numbers in diodes in electric circuits. Arithmetic operations select different circuits to process signals.
Calculators use a metal-oxide semiconductor chip with 28 terminals, four for keyboard, eight for display, eleven for scan lines, one for clock, and three for power.
A timing mechanism at 250,000 cycles per second synchronizes input from display and keyboard, using scan lines. Diodes and keyboard functions can only activate if scan line is on.
Programs can control switching devices {computer}|. Computers are general symbol manipulator.
parts
Computers have a clock, display or printer, registers, adder-subtractor, controller, and program reader. Registers are for display, operand, accumulator, flag, address, and instructions.
functions
Computers have memory, workspace for results {accumulator}, workspace for instructions {instruction register}, arithmetic functions, functions for moving data to and from memory, and logical functions. Computers {von Neumann machine} can perform serial operations using functions, instructions, and accumulator. Serial von Neumann machines can simulate parallel operations, and vice versa.
Machines can duplicate critical functions, have self-repairing abilities, use distributed processing, have independent modules with limited interactions, and use a hierarchy from low-level functions to one high-level function.
error
Computers can have failures {glitch} with unknown causes, usually in flip-flop circuits. Computers can fail to work {down, computer}.
process
Computers can receive physical stimuli and code, store, retrieve, and transform information {computation} {information processing}. Storing and transferring algorithms have timed steps in sequence, typically with logical branches. Algorithms typically have "IF A, THEN B" statements. Computer determines if A is true and then performs B. Algorithms typically have loops: FOR i FROM m TO n, DO x. If value of i is between m and n, computer performs x. That operation changes i. Then computer checks value of i again. Algorithms perform reasoning, mathematical operations, and language processing. They can output information as scripts, images, lists, or tables.
coding
Digital computers typically store and transfer information as positions that can have one of two states {binary coding}.
Computers {digital computer}| can use electronic circuits to perform algorithms on numbers, using electrical binary codes to represent numbers and logical operations. ENIAC was first digital computer [1946].
Computers can perform more than one process simultaneously {hybrid technology multithreaded}| (HTMT).
Entangling many particle states allows solving factoring and other iterative problems {quantum computing}|. Light or particle wave superposition and interference can extract features, as in holograms and database queries.
topology
Topological quantum computing involves topological qubits. Paired excitations in a two-dimensional electron gas {anyon} have world lines that can braid to change topological properties. Knot invariants and quantum two-dimensional surface evolution over time are equivalent. In three dimensions, particles must be fermions, whose wave functions invert when fermion pairs interchange, or bosons, whose wave functions do not change when boson pairs interchange. In two dimensions, particle wave functions can show complex phases when particle pairs interchange. Spin interchanges can be clockwise or counterclockwise. If interchange results in same state, change is Abelian. Topological quantum computing must be non-Abelian to make distinct braids.
Thermal effects can create extra anyons, so temperature must be near 0 K. Larger computers can keep anyon pairs farther apart and at longer distances, to reduce spurious interactions.
Nanometer-size semiconductor crystals {quantum dot}| can change size or properties.
Memories {read-only memory}| (ROM) can stay constant and be only for input.
timer {totalizer}|.
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Date Modified: 2022.0225