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}.
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Date Modified: 2022.0225