110 lines
13 KiB
Markdown
110 lines
13 KiB
Markdown
# Computer
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The word *computer* can be defined in many ways and can also take many different meanings; a somewhat common definition may be this: computer is a machine that automatically performs mathematical computations. We can also see it as a machine for processing [information](information.md), manipulating symbols or, very generally, as any tool that helps computation, in which case one's fingers or even a [mathematical](math.md) formula itself can be considered a computer. Here we are of course mostly concerned with electronic [digital](digital.md) computers.
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We can divide computers based on many attributes, e.g.:
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- by continuous or discrete **representation of data**: [digital](digital.md) vs [analog](analog.md)
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- by **[hardware](hw.md) technology**: [electronic](electronics.md) ("lightning in sand"), [mechanical](mechanical.md), [quantum](quantum.md), biological etc.
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- by **purpose**: special purpose vs general purpose, [personal](pc.md), [server](server.md), [embedded](embedded.md), [workstation](workstation.md), [supercomputers](supercomputer.md), [gaming](game.md) computer etc.
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- by **[programmability](programming.md)**: non-programmable, partially or fully programmable
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- by the theoretical **[model of computation](model_of_computation.md)** it is based on: [Turing machine](turing_machine.md), [lambda calculus](lambda_calculus.md) etc.
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- by **computational power**: how difficult problems the computer is able to solve, i.e. where in the [Chomsky hierarchy](chomsky_hierarchy.md) it stands (typically we want [Turing complete](turing_completeness.md) computers)
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- by **other criteria**: price, reliability, durability etc.
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```
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______________
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| ________ | \_
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| |>.. | | : \ ||
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| | | | : ] |:==-'
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| |________| | :_/ ___||___
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___ |____________|_/'. ___ /########\
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/ \ \ \...../ '. / \ \ |""""""""|
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|;:;| | _____/_____\_____ :|;:;| | |O O O O |
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|;:;| |:|[o][o],,, === | |.'|;:;| | || | | | |
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|___|_| |______________|__|:.|___|_| || | | | |
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__...--': ||,|,|,|,|
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.-''' .-'' \########/
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___________;__ _:_
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/:::::::.::'::/| /-'-)
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/:::::::'.:.::// (___/
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"""""""""""""""
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```
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*On the left typical personal computer, with case, monitor, keyboard, mouse and speakers; on the right a pocket mechanical calculator of the Curta type.*
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Computers are theoretically studied by [computer science](compsci.md). The kind of computer we normally talk about consists of two main parts:
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- **[hardware](hw.md)**: physical parts
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- **[software](sw.md)**: [programs](program.md) executed by the hardware, made by [programmers](programmer.md)
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**The power of computers is limited**, [Alan Turing](turing.md) mathematically proved that there exist problems that can never be completely solved by any [algorithm](algorithm.md), i.e. there are problems a computer (including our [brain](brain.md)) will never be able to solve (even if solution exists). This is related to the fact that the power of mathematics itself is limited in a similar way (see [Godel's theorems](incompleteness_theorems.md)). Turing also invented the theoretical model of a computer called the [Turing machine](turing_machine.md). Besides the mentioned theoretical limitation, many solvable problems may take too long to compute, at least with computers we currently know (see [computational complexity](computational_complexity.md) and [P vs NP](p_vs_np.md)).
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## Typical Computer
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Computers we normally talk about in daily conversations are [electronic](electronics.md) [digital](digital.md) mostly personal computers such as [desktops](desktop.md) and [laptops](laptop.md), possibly also [cell phones](phone.md), [tablets](tablet.md) etc.
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Such a computer consists of some kind of [case](case.md) (chassis), internal [hardware](hardware.md) plus [peripheral devices](peripheral.md) that serve for [input and output](io.md) -- these are for example a [keyboard](keyboard.md) and [mouse](mouse.md) (input devices), a [monitor](monitor.md) (output device) or [harddisk](hdd.md) (input/output device). The internals of the computer normally include:
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- **[motherboard](motherboard.md)**: The main electronic circuit of the computer into which other components are plugged and which creates the network and interfaces that interconnect them (a [chipset](chipset.md)). It contains slots for expansion cards as well as connectors for external devices, e.g. [USB](usb.md). In a small memory on the board there is the most basic software ([firmaware](firmware.md)), such as [BIOS](bios.md), to e.g. enable installation of other software. The board also carries the [clock](clock.md) generator for synchronization of all hardware, heat sensors etc.
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- **[CPU](cpu.md)** (central processing unit): Core of the computer, the chip plugged into motherboard that performs general calculations and which runs [programs](program.md), i.e. [software](sw.md).
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- **[RAM](ram.md)/working memory/main memory**: Lower capacity volatile (temporary, erased when powered off) working memory of the computer, plugged into motherboard. It is used as a "pen and paper" by the CPU when performing calculations.
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- **[disk](disk.md)**: [Non-volatile](volatile.md) (persisting when powered off) large capacity memory for storing [files](file.md) and other [data](data.md), connected to the motherboard via some kind of [bus](bus.md). Different types of disks exist, most commonly [hard disks](hdd.md) and [SSDs](ssd.md).
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- **expansion cards ([GPU](gpu.md), sound card, network card, ...)**: Additional hardware cards plugged into motherboard for either enabling or accelerating specific functionality (e.g. GPU for graphics etc.).
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- **[PSU](psu.md)** (power supply unit): Converts the input electrical power from the plug to the electrical power needed by the computer.
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- other things like fans for [cooling](cooling.md), batteries in laptops etc.
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## Notable Computers
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Here is a list of notable computers.
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{ Some nice list of ancient computers is here: https://xnumber.com/xnumber/frame_malbum.htm. ~drummyfish }
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| name | year | specs (max, approx) | comment |
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| --------------------------------------- | ---- | ------------------------------------------------- | ------------------------------------------------- |
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| [brain](brain.md) |-500M | 86+ billion neurons | biological computer, developed by nature |
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| [abacus](abacus.md) |-2500 | | one of the simplest digital counting tools |
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| Antikythera mechanism | -125 | ~30 gears, largest with 223 teeth | 1st known analog comp., by Greeks (mechanical) |
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| [slide rule](slide_rule.md) | 1620 | | simple tool for multiplication and division |
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| Shickard's calculating clock | 1623 | 17 wheels | 1st known calculator, could multiply, add and sub.|
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| [Arithmometer](arithmometer.md) | 1820 | 6 digit numebrs | 1st commercial calculator (add, sub., mult.) |
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| Difference Engine | 1822 | 8 digit numbers, 24 axles, 96 wheels | mech. digital comp. of polynomials, by Babbage |
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| Analytical Engine design | 1837 | ~16K RAM, 40 digit numbers | 1st general purpose comp, not realized, by Babbage|
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| [nomogram](nomogram.md) | 1884 | | graphical/geometrical tools aiding computation |
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| [Z3](z3.md) | 1941 | 176B RAM, CPU 10Hz 22bit 2600 relays | 1st fully programmable electronic digital computer|
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| [ENIAC](eniac.md) | 1945 | ~85B RAM, ~5KHz CPU, 18000 vaccum tubes | 1st general purpose computer |
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| [PDP](pdp.md) 11 | 1970 | 4M RAM, CPU 1.25Mhz 16bit | legendary [mini](minicomputer.md) |
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| [Apple II](apple_ii.md) | 1977 | 64K RAM, 1MHz CPU 8bit | popular TV-attached home computer by Apple |
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| [Atari](atari.md) 800 | 1979 | 8K RAM, CPU 1.7MHz 8bit | popular TV-attached home computer by Atari |
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| [VIC 20](vic_20.md) | 1980 | 32K RAM, 1MHz CPU 8bit, 20K ROM | successful TV-connected home computer by Commodore|
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| [IBM PC](ibm_pc.md) | 1981 | 256K RAM, CPU 4.7MHz 16bit, BASIC, DOS | 1st personal computer as we know it now, modular |
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| [Commodore 64](c64.md) | 1982 | 64K RAM, 20K ROM, CPU 1MHz 8bit | very popular TV-connected home computer |
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| [ZX Spectrum](zx_spectrum.md) | 1982 | 128K RAM, CPU 3.5MHz 8bit, 256x192 screen | successful UK TV-connected home comp. by Sinclair |
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| [NES](nes.md)/Famicom | 1983 | 2K RAM, 2K VRAM, CPU 1.7MHz 8bit, PPU | TV-connected Nintendo game console |
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| [Macintosh](macintosh.md) | 1984 | 128K RAM, CPU 7MHz 32bit, floppy, 512x342 | very popular personal computer by Apple |
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| [Amiga](amiga.md) | 1985 | 256K RAM, 256K ROM, CPU 7MHz 16bit, AmigaOS | personal compuer by Commodore, ahead of its time |
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| [NeXT](next.md) | 1988 | 8M RAM, 256M drive, CPU 25MHz 32bit, NeXTSTEP OS | famous workstation, used e.g. for Doom dev. |
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| [SNES](snes.md) | 1990 | 128K RAM, 64K VRAM, CPU 21MHz 16bit | game console, NES successor |
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| [PlayStation](playstation.md) | 1994 | 2M RAM, 1M VRAM, CPU 33MHz 32bit, CD-ROM | popular TV-connected game console by Sony |
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| [TI](texas_instruments.md)-80 | 1995 | 7K RAM, CPU 980KHz, 48x64 1bit screen | famous programmable graphing calculator |
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| [Deep Blue](deep_blue.md) | 1995 | 30 128MHz CPUs, ~11 GFLOPS | 1st computer to defeat world chess champion |
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| [Nintendo 64](n64.md) | 1996 | 8M RAM, CPU 93MHz 64bit, 64M ROM cartr. | famous TV-connected game console |
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| [GameBoy Color](gbc.md) | 1998 | 32K RAM, 16K VRAM, CPU 2MHz 8bit, 160x144 | handheld gaming console by Ninetendo |
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| [GameBoy Advance](gba.md) | 2001 | ~256K RAM, 96K VRAM, CPU 16MHz 32bit ARM, 240x160 | successor to GBC |
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| [Xbox](xbox.md) | 2001 | 64M RAM, CPU 733MHz Pentium III | TV-connected game console by Micro$oft |
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| [Nintendo DS](nds.md) | 2004 | 4M RAM, 256K ROM, CPU ARM 67MHz, touchscreen | famous handheld game console by Nintendo |
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| [Nintendo Wii](wii.md) | 2006 | 24M RAM, 512M ROM, SD, CPU PPC 729M | famous family TV console with "stick" controllers |
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| [iPhone](iphone.md) (aka spyphone) | 2007 | 128M RAM, CPU ARM 620MHz, GPU, cam., Wifi, 480x320| 1st of the harmful Apple "smartphones" |
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| [ThinkPad](thinkpad.md) X200 | 2008 | 8G RAM, CPU 2.6GHz, Wifi | legendary laptop, great constr., freedom friendly |
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| [ThinkPad](thinkpad.md) T400 | 2008 | 8G RAM, CPU 2.8GHz, Wifi | legendary laptop, great constr., freedom friendly |
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| [Raspberry Pi 3](rpi.md) | 2016 | 1G RAM, CPU 1.4GHz ARM, Wifi | very popular tiny inexpensive SBC |
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| [Arduboy](arduboy.md) | 2016 | 2.5K RAM, CPU 16MHz AVR 8bit, 1b display | tiny Arduino [open console](open_console.md) |
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| [Pokitto](pokitto.md) | 2017 | 36K RAM, 256K ROM, CPU 72MHz ARM | indie educational [open console](open_console.md) |
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| [Raspberry Pi 4](rpi.md) | 2019 | 8G RAM, CPU 1.5GHz ARM, Wifi | tiny inexpensive SBC, usable as desktop |
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| [Deep Thought](deep_thought.md) | | | fictional computer from Hitchhiker's Guide ... |
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| [HAL 9000](hal_9000.md) | | | fictional AI computer (2001: A Space Oddysey) |
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|[PD computer](public_domain_computer.md) | | | planned LRS computer |
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|[Turing machine](turing_machine.md) | | | important theoretical computer by Alan Turing |
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TODO: mnt reform 2, pinephone, 3DO, ti-89, quantum?
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