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#Post#: 312--------------------------------------------------
The Personal Computer Explained
By: Red Date: April 15, 2013, 2:17 pm
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I take it most of the people on this forum own a computer or
something that's the functionally equivalent. Since I'm bored at
work, I'm going to explain just what a computer is and how it
operates. I'll go in depth, but hopefully not so much that
people feel overwhelmed. Let's begin.
The first question I must answer is what a computer really is.
What constitutes a computer? Is a calculator a computer or
something else? What about an xbox360? To answer this, I'll take
a short clip from Wikipedia:
[quote]
"A computer is a general purpose device that can be programmed
to carry out a finite set of arithmetic or logical operations.
Since a sequence of operations can be readily changed, the
computer can solve more than one kind of problem."
[/quote]
By this definition, a couple things can be implied. First, a
computer has some sort of device that can read a sequence, and
secondly, they have some sort of memory. These two elements are
a fantastic place to start.
Most computers today run off of a digital electrical circuit,
which uses the frequency of an electrical current to define bits
of data. I'd bet $100 that the computing device you're using
right now is digital, and is not running off of water or
something weird. That's not to say that a computer can't be made
with water, but for now I'll just cover the electronic type of
computer.
At it's most basic, an electronic computer consists of a power
supply, a CPU or Central Processing Unit, and a type of memory.
We can skip out on explaining what a power supply is, because
that should be obvious, but what the hell does a CPU actually
do? How does it think? Is it conscious? Well, I can't answer the
last question for you, but I can tell you how it's built. A
modern day CPU has several components, and among them reside a
program counter/control unit, a memory bus, some embedded
memory, and an ALU or Arithmetic Logic Unit. The computer's
design is very much theoretical in the sense that someone had to
conceptualize exactly how data could be processed and used for
instructions to do things. We can credit the guy who made the
Turing Machine for fathering these kinds of devices. In concept,
the turing machine took a set of instructions and operated
accordingly after reading input from them, much in the same way
a computer's CPU does. The program counter takes instructions
from different bits of data, 1s and 0s, stored in memory to
complete certain tasks. If the program counter gets a certain
opcode, or Operation code, it reads it as an instruction and
acts accordingly.
One of the most basic languages out there is called Assembly
Language. It's not all binary, or consisting or 1s and 0s, but
it operates at a slightly easier level to understand with
hexadecimal numbers. Hexadecimal is similar to the decimal
counting system that we learn in kindergarten, but works better
for computers for a number of reasons.
See, computers, at the hardware level, think in Binary, or 1s
and 0s. You can also think of this as On and Off, and True and
False. You also may have heard that a computer is 64 or 32-bit,
which means it can take instructions that are 64 or 32 bits
long. What is a bit? A bit of data is a single 1 or a single 0.
And 8-bit computer, for example, would read instructions as
01100101. That would be the equivalent to one Byte of data. A
Byte is made up of eight bits. To put this into perspective, a
single letter is about one Byte of data. Computers read a
collection of Bytes as a Word, but we don't have to get into
that. Words have variable length depending on the CPU.
Okay, so I still haven't explained why hexadecimal matters...
Continuing, computer data is normally stored on an array of
memory. Hexadecimal, which counts to 16 instead of 10, works
well because 1, the most 4 bits of binary can count is to 16,
and 2, memory uses what's called addresses, which are
hexadecimal numbers. Also, as an added note, zero is a number
for binary and Hex. Let's take a second to delve into these
systems for a moment.
These numbers works like this:
----
Decimal Number - Binary Number - Hex Number
----
0 - 0000 - 00
1 - 0001 - 01
2 - 0010 - 02
3 - 0011 - 03
4 - 0100 - 04
5 - 0101 - 05
6 - 0110 - 06
7 - 0111 - 07
8 - 1000 - 08
9 - 1001 - 09
10 - 1010 - 0A
11 - 1011 - 0B
12 - 1100 - 0C
13 - 1101 - 0D
14 - 1110 - 0E
15 - 1111 - 0F
16 - 10000 - 10
17 - 10001 - 11
Hopefully that makes sense of how things work a little better.
So your CPU takes these hex numbers which are actually binary
bits stored in memory, and shoots them through the program
counter and reads them, then processes and executes the
instructions.
Without memory, your computer wouldn't really be good for much.
Most of what a computer does relies on some form of memory, but
the most common is RAM or ROM. These have two different
functions. ROM or Read Only Memory, is a type of hardware that
is normally only utilized as unchangeable code. Think of old
gameboy cartridges. They have a ROM and RAM in them. The ROM
stores the actual game code itself, and can't be erased or
written to easily. RAM or Random Access Memory, on the other
hand, is easily writable and can be thought about as the
"workbench" of a computer. The biggest difference between ROM
and RAM is that RAM is not what you'd call persistent. Any
values it stores are lost as soon as the RAM looses power. RAM
is used in gameboy cartridges to store save files, because those
are easily writable and changeable, and must be dynamic so that
the game can store where exactly you left your character on the
map.
Other computers use RAM to run other applications, for example,
like Photoshop or Firefox. Now, I mentioned that ROM wasn't
easily writable, so how do we store those programs like Firefox
and Photoshop? Shouldn't they disappear if we download them to
RAM?
The answer is, we don't download them to RAM or to ROM. Instead,
they go directly to the HDD, or Hard Disk Drive, often shortened
to Hard Drive. The hard drive is actually a pretty neat device.
It stores data as magnetic fields on several thin metal
cylinders. It has different sectors that it can write to, erase,
and reserve for data. Not all computers have a HDD. Some
computers run off of SSDs instead, or Solid State Drives. These
drives are quicker to access than an HDD, since it's using a
similar memory type as RAM and ROM. This type of memory is
called FLASH storage. You know what a flash drive is, or an SD
card is, right? If not, look them up. These devices use FLASH
memory since it's easily writable and also persistent, which
means it can store whatever we want for a long amount of time.
Now, you may ask, "Why doesn't everyone just use FLASH and make
it easy?" The reason we don't use flash for every situation
imaginable is because it can oftentimes be more expensive than
RAM or ROM, and it may also have a lower life expectancy than
RAM. The chips (called ICs or Integrated Circuits) that store
the FLASH memory in them only have a certain amount of integrity
and can only handle so many Reads and Writes. After that amount,
there's no guarantee that the device will hold the right data.
Given, this value is normally in the hundreds of thousands and
pushing millions, that can often be used up fairly quickly
depending on what that device is used for. RAM and ROM are
affected by this too, with ROM having imaginably significantly
lower writes that it can handle than RAM. With hard drives,
hardware failure can be relatively common compared to the other
memory options, but not common enough for us to throw them out
completely.
Another type of memory is external storage. These are normally
utilized and peripherals to the computer's system, such as
CD/DVD drives and USB drives. Why don't we just store systems on
CDs, you may ask? Well, for one thing, they're an external
medium of storage, meaning that they can be easily removed. This
makes them subject to the elements and people and stuff, and are
pretty volatile, so if they get scratched, suddenly your whole
system could be gone if you stored it on a CD. Additionally,
they don't have a very large capacity relative to today's
software requirements and relative to other hardware options.
It's becoming more and more common for computers to have upwards
of 500 gigabytes, or 1,000,000,000 bytes of storage, and CDs
normally only hold about .7 of a gig. DVD disks hold about 4
gigs, but that's still a deficient amount necessary.
As well as having a smaller capacity, CDs usually have a slower
read and write speeds compared to HDDs, and where HDDs can store
info on both sides of a cylinder, a CD has only one writable,
and therefore readable surface.
There's a biiiig hole in this explanation so far, and you
probably can see it, because you're looking through a screen,
and I haven't explained how they work.
Screens, keyboards, mice or track-pads, and speakers aren't
fundamental to the definition of what a computer is. Many
computers, such as those used as web-servers or in
supercomputers, don't always have any directly connected
graphical interface hardware, and can run fine without them
usually. These computers are usually accessed over some sort of
network, but even the ability to network with other computers
doesn't define them. The desktop computer only became classified
as a communication device within the last three to four decades,
and it has existed long before then.
Graphical interfaces clearly revolutionized how we perceive
computers, and we still haven't mastered the art of roping in
all of their potential. People can spend more money on simply a
graphics card than for their actual computing system. Bigger
computers and most laptops have a separate chip from the CPU
called a GPU (do the math). This chip is commonly more powerful
than the CPU as far as how fast it operates and the like. If
your computer doesn't have an on-board graphics card (or a
graphics processor on the motherboard), as many older computers
don't, if you want to see anything on a screen, you'd need to
install one into what's called a PCI port. Just like a USB port,
these help connect peripherals to your system, but are located
internally, directly on the motherboard.
The different connection types that are used are VGA, being
really common, DVI, being fairly common, and HDMI, being
probably less common. Out of all three of these, HDMI is the
only one designed to transmit sound as well as graphics, I
believe, which may also function if the graphics card has
support for it.
Aside from the computer itself, screens and graphical monitors
also have a bunch more details. You may have heard of 720 or
1080p or 1080i video. I won't get into the difference between
1080p and 1080i, but the point is, these are all video
resolutions. Screens are made of pixels, or individual dots that
are arranged in some sort of array across your screen, so what
you're seeing right now is actually a whole bunch of dots
working together to help form letters and communicate things and
it all gets really meta from there. Most commonly, screens are
LCDs, or Liquid Crystal Displays. These crystals are really
fancy, and change color as they're electrically charged. They
are usually lit by LEDs or some lights behind them. More about
pixels, a single colorful pixel is made up of three different
sections. One glows blue, the other red, and the other,
something close to green or yellow. These are, obviously,
primary colors, and are used to make the colors you see on your
screen by varying intensity and stuff.
The resolution of your screen can effect how you see things
projected onto it. If you don't use the optimum or recommended
resolution for your screen, you can get shaky or poorly colored
picture. Screens also operate at a certain frequency that is the
rate at which they refresh. 60Hz is very common, and if 1Hz unit
is one change per second, 60 means 60 changes per second. When
you're watching video, the camera records at a certain frame
rate, or frames per second. If you watch a video on your
computer that's 24fps on a 60Hz screen, you should be fine, but
if you watch a 60fps video on a 30Hz screen (not that this is
really practical), your image might be really choppy compared to
what was initially recorded. (Most cameras that are not HD
record at 24fps, so viewing a video at optimum quality is
normally not an issue if you leave out the initial resolution
and if you're watching it on the internet or something. Watching
a 1080p video or 4k (another resolution) video at 60fps may put
a huge strain on your computer's resources though, depending on
your hardware.
Audio interfaces are dumb and simple usually - no need to over
complicate them. Digital signals are translated into analogue
and then sent through an amplifier which goes to the speakers
which vibrate at the frequency of the sound. Yay. Microphones
are the literal opposite of this, so if you're wondering how
they work, read it backwards. Yes, speakers are actually
microphones (kinda).
With the advent of USB, keyboards and mice aren't so hard to
understand. They take your input, which is basically just you
pressing button which completes a circuit, and sends it through
a piece of software known as a Driver (which is really
confusing, because you have pieces of hardware called drivers
and software called drivers now), and translates that as output
on the screen.
That's about it! If there's anything I missed or anything I need
to clarify, please respond in this thread. Also, same thing for
any questions, if you have any. Don't be afraid to ask, because
not only do I enjoy answering questions, but if you can think of
it, chances are someone else is thinking of something similar to
ask. Yay!
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