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How Computers Work Tutorial #1

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SourC00kie avatar SourC00kie
Retired Moderator
Level 45 : Master Blob

Computers are the most complex machines that have ever been created. Very few people really know how they work. This book will tell you how they work and no technical knowledge is required. It explains the operation of a simple, but fully functional, computer in complete detail. The simple computer described consists mainly of a processor and main memory. Relays, which are explained, are used in the circuitry instead of transistors for simplicity. This book does not cover peripherals like modems, mice, disk drives, or monitors.

Did you ever wonder what a bit, a pixel, a latch, a word (of memory), a data bus, an address bus, a memory, a register, a processor, a timing diagram, a clock (of a processor), an instruction, or machine code is? Though most explanations of how computers work are a lot of analogies or require a background in electrical engineering, these tutorials will tell you precisely what each of them is and how each of them works without requiring any previous knowledge of computers or electronics. However, these tutorials start out very easy and get harder as it goes along. You must read each tutorial starting at number one and not skip around because later topics depend on understanding earlier topics. How far you can get may depend on your background. A junior high school science background should be enough. There is no mathematics required other than simple addition and multiplication. These are short tutorials, but it must be studied carefully. This means that you will have to read some parts more than once to understand them. Get as far as you can. You will be much more knowledgeable about how computers work when you are done than when you started, even if you are not able to get through the whole text. These are technical tutorials though it is aimed at a non-technical audience. Though these tutorials takes considerable effort to understand, it is very easy for what it explains. After you have studied the tutorials, if you go back and read them, it will seem simple. Good luck!

Computer Hardware

The computer is an amazingly useful general-purpose technology, to the point that now cameras, phones, thermostats .. these are all now little computers. This section will cover a lot of ground, introducing major parts and themes of how computer hardware works. "Hardware" refers the physical parts of the computer, and the late "software" page will talk about the code that runs on the computer. These are deep and complicated topics, but many of the basic principles make perfect sense and will give you an insight about what's going on behind the curtain.

Chips and Transistors

Modern computers use tiny electronic components which can be etched onto the surface of a silicon chip. By far the most common electronic component is the "transistor" which works as a sort of valve for a flow of electrons. The transistor is a "solid state" device with no moving parts; it is a basic building block used to construct more complex components. In particular, a "bit" (below) can be built with an arrangement of 5 transistors. The transistor was invented in the early 1950's, replacing the vacuum tube. Since then, transistors have been made smaller and smaller, allowing more and more of them to be etched onto a silicon chip.

Moore's Law

Moore's law states that the density of transistors on a chip doubles about every 18 months. It is not a scientific law, just a broad prediction that seems to keep working. More broadly, it captures the idea that per dollar, computer technology (not just transistors) gets exponentially better as time goes along. This is quite clear if you look at the cost or capability of computers/cameras etc. you have owned. It might mean that each new generation of computer is faster. OR it could mean that keeping capability constant, computers get cheaper and cheaper .. showing up in more in more contexts as it becomes cost effective (e.g. in your car, your thermostat, ..).

Computer Hardware

  • CPU Central Processing Unit -- inevitable referred to as the "brains" of the computers. The CPU does the active "running" of code, manipulating data, while the other components have a more passive role, such as storing data.
  • RAM "Random access memory", or just "memory". RAM is the working scratchpad memory the computer uses to store code and data. RAM is effectively a large storage space of "bytes" under the control of the CPU. RAM is relatively fast, able to retrieve the value of any particular byte in a few nanoseconds (1 nanosecond = 1 billionth of a second). The other main feature of RAM is that it only keeps its state so long as it is supplied with power. It is not "persistent". Suppose you are working on your computer and it suddenly loses power and the screen goes blank. You understand that what you were working on is gone .. RAM has been wiped clean, leaving you only with what you last saved to disk.
  • Hard Disk or Flash Memory "persistent storage", typically today on a computer provided by a spinning hard disk (also known as "hard drive"), or by "flash memory". The hard disk reads and writes magnetic patterns on a spinning metal disk to store bits, while flash memory is "solid state" .. no moving parts, just silicon chips to store bits. In either case, the storage is persistent, in that it maintain its state even when the power is off. Flash memory (also known as a "flash drive", typically in the form of a usb key) is persistent like a hard disk, and is faster and uses less power than a hard disk. However, per byte, flash is significantly more expensive than hard disk storage. Flash memory has been getting cheaper, so it may take over niches at the expense of hard drives. Flash memory is much slower than RAM memory, so it is not a good replacement for RAM. (Note that Adobe "flash" is unrelated; it is a proprietary media format.)
  • File System The hard disk or flash memory provides persistent storage as a flat, undifferentiated collection of bytes without any organizational structure. Typically the hard disk or flash memory is formatted with a "file system" which organizes the bytes into the familiar pattern of files and directories, where each file and directory has a somewhat useful name like "resume-2010.txt". Essentially, each file refers to a block of bytes, so the "flowers.jpg" name refers to a block of 48KB of bytes which are the data of that image. The file system in effect gives the user a name (and probably an icon) for a block of data bytes, and allows them to do operations on that data, like move it or copy it or open it with a program. The file system also tracks "meta information" about the bytes: how many there are, the time they were last modified.

    Microsoft uses the proprietary NTFS file system, and Mac OS X has its Apple proprietary HFS+ equivalent. Many devices (cameras, MP3 players) use the very old Microsoft FAT32 file system on their flash cards. FAT32 is an old and primitive file system, but it is good where wide support is important (Microsoft claims to hold patents needed to read or write FAT32, but it is widely implemented anyway). Proprietary/patented formats and the goal of moving and interchanging your own data are a bad combination .. we'll look at this later.


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07/02/2013 4:21 pm
Level 44 : Master Engineer
DeadSpaceDUde avatar
you do not know how computers work. I have a bachelors degree in computer science and my A+ certification. Before all you say "Well then why are you on pmc!" I will just say, I LOVE MINECRAFT!!! However back to the point, you are so far off from the truth, It is funny.
07/03/2012 12:17 am
Level 44 : Master Sweetheart
Dinodaw avatar
My brother is going to build a computer.
03/26/2012 3:33 pm
Level 87 : Elite Programmer
micdoodle8 avatar
They have a giant poster in my HS computer lab like the image of this blog. I was like "Really?".

Anyway, nice tutorial :D
03/16/2012 6:58 pm
Level 15 : Journeyman Artist
EyeOfNeptune avatar
You forgot to include a little bit of information on the LINUX OS in the last part of this article
It's something that you should research if you've never heard of it
01/26/2012 1:53 am
Level 22 : Expert Geek
superman11 avatar
copyright, this is stolen content
02/16/2012 6:57 pm
Level 15 : Journeyman Taco
FantasticHaterade avatar
hahaha your an idiot
01/23/2012 4:32 pm
Level 31 : Artisan Theorist
Theodor488 avatar
Really answered a lot of questions I had thanks.
12/31/2011 1:13 am
Level 30 : Artisan Toast
Conquer avatar
So you fully understand computers?
12/30/2011 5:33 pm
Level 21 : Expert Unicorn
bloodhound64 avatar
Um why need this if your using a computerr... WAIT you show this to people who dont know what they are!
12/24/2011 2:41 am
Level 24 : Expert Narwhal
x_creeper! avatar
Me liek.
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