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Computers - General
The advent of computers have had and will continue to have dramatic impacts on the world. Although (what we might want to call) computers first appeared on the scene around the 1940's, was it not until the advent of the PC by IBM and software like Visicalc (the first popular spreadsheet program) and word-processing program around 1980 that rocketed computers into the world.
Here we look at COMPUTERS in general, the HARDWARE, the SOFTWARE, NETWORKING and the INTERNET
What is so wonderful about computers? Well, firstly are they fast and can do millions of calculations per second, or follow millions of instructions ...... that's nice. In fact that gives us a slightly better hint of what computers are ..... apart from numbercrunchers, do they follow instructions very closely.
But more importantly, are they very versatile.... they can be changed / updated quite easily (more so than any other kind of machine that preceded it) ..... and this is all done through programming and programs.
Still not sure why computers are so important? Well, because through programming can the instructions that they follow be changed very easily. I remember in the good ole days how the technician on our accounting machine, adjusted the way it worked by changing a few gears!
Now, (take cell-phone) companies can introduce a whole variety of (say) billing options by simply editing their programs, not to mention banks, insurance companies, stock exchanges, you name it....
What are the major aspects of computers, well there is the HARDWARE, the SOFTWARE, and then is there the INTERNET
HOW DO COMPUTERS WORK
Computers are essentiall very dumb electrical machines that contain a lot of switches...... yes that's right, computers can really only count to 1. Well, actually can they distinguish between 0 and 1, when a switch is open does it mean 0 and when the switch is closed does it mean 1...... and this is called 1 BIT, and counting in zeros and ones is referred to a a BINARY system.
Computers are however very powefull because they actually have thousands if not millions of these switches that can open and close thousands if not millions of times per second (400 MHz means 400 million times per second!)This is mainly how the CPU is rated and what it does, which we come to a little later
And that really makes them quite powerfull.
Add to that powerfull programs, and you might get close to being able to call computers clever.
But now, how do computers work with all those zeros and ones.
Well, the hardware puts eight of these switches (BITS) together, and with each BIT (switch) having a value of 0 or 1, can a combination of 256 possible meanings or values be donated, and this is called 1 BYTE. Incidentally, each letter you see in front of you on the screen takes up 1 Byte. To record the value of such a BYTE in the Binary system is a bit cumbersome, requiring 8 digits comprising of zeros or ones. Instead was the HEXADECIMAL system devised where we count in units of 16 (not 10 like in our normal decimal system). A two digit hexadecimal value can instead be used, and your are welcome to try an figure out how it all fits together, and if you can't, just remember that two hexadecimal values each able to take 16 values each, can give you 16 x 16 = 256 possible values!
And how in the world do we count in units of 16....... well this is how the clever people figured it....
0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F which takes us to 16, and then
10,11,12,13,14,15,16,18,19,1A,1B,1C,1D,1E,1F which takes us to 32
and as said earlier, two digits like this can give us 256 possible combinations
if you're confused, well dont worry, I've given you the basics and you will have to go and figure out in the privacy of your bedroom how it all fits together!
Here is a question you might ponder over once you think you've figured it all out.....
We know that a kilo stands for 1000, and Mega for 1 million, but why is there not exactly 1000 Bytes in a kiloByte, and why not 1 million Bytes in a MegaByte?
Having taken a micro look at how computers work, be aware that it's not quite as simple as was explained above...... those are just the basics, and the people that first built computers are actually very very clever ..... more than all of us mere mortals put together!
But let's now take a broader (macro) view of computers, in terms of their major components.... at least that's something we can understand quite well.
The CPU (Central Processing Unit)
This is the unit that contains all tose switches we spoke about, and is really the things that processes the information
The Storage Units
We should not be too surprised to find out that the CPU looses whatever information it has inside it when you switch off the computer. So we need something that can save the information, even when the computer is off. Such information can be saved in a variety of ways, the most common way was on what's known as a disc. A disc is simply something onto which magnetic impulses are put, signifying a 1, and where there are no magnetic impulses signifying a zero..... which shouldn't surprise you because remember that's the basis on which a computer works anyway. The disc rotates and a head either reads or writes the magnetic impulses ...... nearly like the old tape recorders.
Orginally discs were made out of a thin plastic in a sleeve, and called Floppy or Stiffy Discs, but with rather small storage capacity (by computer standards anyway 360 kBytes being 360,000 Bytes, or 1,4 MBytes being 1,400,000 or 1,4 million Bytes). The most popular Discs are however made out of metal in a metal enclosure and have capacities as high as 50 GBytes being 50,000 million Bytes
Storgae Units come in other mechanisms, like.....
CDs which store the information instead in marks that are burnt onto the CD, and dont be surprised to find out that a mark signifies a 1 and the absence of a mark a zero.
Electronic units consisting of millions of switches that remain in a particular position, even when the power to it is switched off. These units are more reliable because they have no moving parts, and are becoming more popular lately.
If these Storage Units can be removed from the computer are they called Removable Media, and then be used to Backup information, and keep separate from the computer (in case the computer is stolen or the hard disc fails), and/or be loaded onto another computer where it can then be used again ....... wonderfull, isn't it?
Quite a bit to Storage Units!
The Power Supply
That's the big box in the corner, and it's mainly a kind of transformer...... which reduces the 200V alternating current to around 1 or 2 Volts ...... current, which is the kind of power that computers use to function.
Be careful with this unit, although the outlet Voltage is very low and cannot harm you, is the inlet Voltage 220 Volt which can kill you if you touch any of these wires.
The Mother Board
This is the big electrical board inside the computer that everything is basically plugged into
These are not playing cards, but the name given to those smaller electrical boards that plug / push into the Motherboard.
Computers are generally modular, ie. made up of various components that can be interchanged. Not only does it allow more flexibility, but also cuts down on the repair costs by only having to replace one faulty component instead of your whole computer.
These Cards serve different purposes, but mainly are used for plugging other things (peripherals) into your computer, so the one end of the Card normally sticks out at the back of your computer and contains one kind of plug or another.
Sometimes are these Cards integrated into the motherboard, which is nice but if it gives a problem must the whole motherboard often be replaced!
And then, some of the peripherals...
That's the unit which is mainly used to communicate to the computer, although there are other ways in which this can be done, most notably by simply talking to it.
Another mechanism that we use to communicate with the Computer. Clever little animal, hey?
The computer people call this the monitor, but that's just to try and impress us non-professionals. What's more important to know, is that thuis is how the computer communicates with us.
Well, that's another device that the computer uses to communicate with us, and essentially puts the information on paper.
Plugs (ports) and Cables
Various types of Plugs and Cables are used on a Computer.
Port is fancy word used to describe the electrical route that the signal follows
Originally was there .....
-The Parallel Port, consisting of a 25 pin rectangular plug, with the computer having a female end, and the cable a male end. These ports / plugs conveyed the signal in a ________ manner. Various types of parallel cable was used, dpending on what the other end of the cable looked like.
If used for connecting printers, did the cable have a "special printer" type plug on the other end.
If it was used to connect to a splitter box ..... did it have another 25 pin male plug at it's other end
-The Serial Port, also consisting of a 25 pin rectangular plug, but the computer had a male end, and the cable a female end. Various types of Serial cables were used, depending on what the other end looked like....
If it also had another male plugs at it's other end, was it know as a end at the ohad a also known as a RS232 cable. These ports conveyed the signal in a serial manner, and was mainly used to connect extrnal modems to a computer, although it was sometimes used to also connecet a printer to the computer if the printer had a serial connecetion instead of the "special printer" plug
The Serial and the Parallel plugs looked virtually identical, but because the one had a female end and the other a male end, could they never be used incorrectly, unless your were silly enough to plug the one cable into the other!
-The USB plug / port
USB stands for Universal Serial Bus, and is a more modern connection, because in comparison to the older type Parallel and Serial Ports .....
+it is smaller and lighter
+can be plugged and unplugged while the computer and peripheral is switched on
+can convey information much faster
.... as a result will it probably in time phase out the older type Parallel and Serial plugs
Well we all now know what the Software is ...... nl. the programs that run on the computer and essentially gets the copmputer to do things for us. Programs are really sets of instructions in computer language that tells the computer what to do.
This is essentially the first program that is loaded onto a computer, and provides the basis on which all other programs run. The Operating system isn't really important because you dont raelly see it or use it when you run your other programs, but it's actually quite important for the people that write the programs that you ultimately use.
The first popular Operating System was DOS (Disk Operating System), and the one that everyone now uses is called Windows ....... which is not really that different from what DOS gave us, except it's a lot more powerfull and has a very nice and colourful visual interface.
Windows also popularized the ability of a computer to do multi-tasking, especially in it's ability to have two or more programs running similtanously and especially being able to access or see both programs on the screen ...... from there came the word Windows, although these Windows Operating Systems could a lot more than just that!
Many programs are available, and we dont want to ask too many questions about them, other than what they can do for us.
Most common programs are .... starting from the most basic:
-Word processing programs: this simply allows us to use our computer as a (very powerfull) typewriter, because unlike a typewriter can we see what we type on the screen, print it out, edit (change) it, save it to access later, not even to mention all the powerfull features that modern word pressing programs give us like different fonts, letter sizes, etc.
-Spreadsheet programs: these are programs that allow us to put information in rows and columns and are mainly used to do powerfull arithmetic calculations
-Database programs: these are programs that specialize in accepting large amounts of data, and being able to sort and search for particular groups of information, and provide it to the user.
-And then there are hundreds of other types of programs, ie. fax programs, and last but not least games.
Programs are written / created using other programs...... lets look a little closer at these "other programs" called programming languages
+Computers were originally programmed in simple computer languages known as 1st generation languages, and although very powerful because you could really talk directly to the CPU of the computer, are these langauage very complicated and quite limited in what the can do.
+Second Generation languages were developed which was more like a language we speak, one known as ASSEMBLY language, was easier to use, but still very complicated
+Third Generation languages which were even more like a language we speak, developed because we want to make things easier for ourselves, and in the process actually managed to make the language more powerfull in the sense that it could do more with fewer progarmming actions. These are known as high-level languages and the original languages were FORTAN, COBOL, etc. Then a language called BASIC was developed which was a big improvement, and from that followed languages like C, C++, Java, etc. There have been over the years developments in these languages to make them especially more powerful, especially when the world converted to the new fad of Windows
+Fourth Generation languages were developed that were even closer to the language we speak, and were mainly used for accessing information in large Databases.
+Fifth Generation languages are those languages that are used in an attempt to create artificial intelligence in computers..... quite something else than just the already powerful other languages!
The instructions of the program that we write, is called the Source Code.
Programs can be interpreters, in which case they simply convert these instructions into computer language and executes the program. The problem with this kind of program is that it is rather slow, but more importantly can everyone see your Source Code.
More modern programs are therefore compiled, ie. converted into computer langauge before distributed. These programs are obviously faster, and the Source Code is not available.
If you thought computers were complicated before, then wait until people wanted to start connecting them together!
In the beginning were computers standalone units that did something. Then people started connecting terminals to this computer (called a main frame) so that more than one person could use it at the same time. But these main frames were big and very expensive, so their use was limited to big organisations that could afford them.
But then companies like IBM and Apple came out in the 1980's with what they called the Personal Computer (PC). This was a much smaller unit, much cheaper because they were produced in mass, but more importantly was it a relatively simple unit which only one person at a time could use .... hence the name Personal Computer. In spite of this one limitation was it otherwise a major success and brought about the biggest revolution the world had ever experienced.
But mankind is never satisfied with what it has, and soon afterwards did people want to start interconnecting these PC's. This proved to be quite a challenge because the PC was never designed to be able to do this, and when companies first managed it, was it quite something. The name NETWORK was given to such computers connected together.
At time wnet by did two types of networks ensue....
-The Peer to Peer network, where computers were simply connected together and you could access the information on one from another ...... which was very usefull
-The Server based network, where all information was essentially stored on one or more centarl computers, and the other computers simply accessed the information...... which was similar to the old mainframe computer systems, except it consisted of PC's and was a lot cheaper
In time, was all computer systems going to go this way, instead of building larger computers, would we simply just interconnect more computers ..... modularity on a large scale.
What is the Internet, or the Web.... and what's the difference?
Well, the Internet is essentailly thousands (well these days more like millions) of computers that can communicate with each other via telephone lines, worldwide ..... which you might call the hardware.
The Internet originated in the USA Department of Defence, who wanted to create a computer system that was not dependent on only one machine. Essentially did they want to connect computers that were in different remote locations and why not just use conventional telephone lines. I guess you could call this the first Wide Area Network (WAN)
But it's really the software that makes it all work, and over time did certain standards develop, the most important piece of sotware being what became known as TCP/IP.
+TCP stands for Transmission Control Protocol, and essentially manages the packets of information being sent.
+IP stands for Internet Protocol, and essentially manages the addresses that informtaion is sent to.
This TCP/IP must be quite something, allowing computers world wide to effortlessly communicate with each other!
So, in simple terms does the Internet consist of thousands of Servers on the one hand, and computer users like us with telephone (and modem) connections to our ISP's. Our ISP's then have the software and facilities to route information between us and all these servers .....at the same speed that it takes for a voice signal to travel!
The above is all good and well, but does anyone (except the real specialists) know how information actually finds it's way from one ISP to (say) another ISP or server halfway across the world?
The Internet consists of various specialized systems, the most common one being one where information can be accessed via "hypertext" ..... this is called the World Wide Web (WWW or just The Web). This method of information transfer was essentially developed around 1989 by Tim Berners-Lee in Switzerland.
Various methods (protocols) of information sending has developed and has become available on the Web, ie.
-Hyper Text Transfer Protocol, abbreviated HTTP, addresses starting with http://. Allows information to be displayed in the form of pages.
-File Transfer, using the FTP Protocol, and it's Internet address starting with ftp://.
How is an Internet Address made up? It essentailly looks like this...
+The protocol is the software system through which the connection is made, in this case http
+The servername can be anything, but the first server in most organisations are named www
+The domainname is essentially the registered address of the server, and normally consists of at least 2 but sometimes more parts separated by dots, ie. mweb.co.za or hello.com or dept.org or learn.edu.uk
the first part being the name, the second part consisting of reserved abbreviations indicating it's type of "business" and the third part a country code if further differentiation is required
+The directoryname/filename takes you to a particular place on the server, but is optional since most servers are set up to take you to an index page if no specific page is specified.
By now should it hopefully be obvious that all information on the Internet, or particularly the Web consists of files in one or another directory of a server, which is displayed as a page on the screen of your computer.
But there is more on the Internet ......
-Email using the SMTP or POP Protocols, using the format username@domainname
In closing, is a special program needed to actually connecet to and access facilities on the Internet, and various such programs are available. In the case of accessing the Internet via the WWW, are such programs available free of charge, the most common one's being Microsoft Internet Explorer, and Netscape Internet Navigator
This is a good time to talk about the Modem, because although a peripheral or component of a computer, is it really only used to connect to the Internet. Modem stands for ________, and essentially converts computer information into a format that can be transmitted along a telephone line, and at the other end back into computer information.
What is particularly important about this is that information / signals can travel along telephone wires / lines at a very high speed (just think how fast considering that you can have a normal conversation with someone who is 500 km away, or even on the other side of the world....... that's like tens of thousands of kilometers per SECOND! It is largely this feature that made the Internet a reality.
Web authoring is very similar to writing Custom Programs, except a whole new dimension needs to be added, and therefore have I chosen to treat it separately
Web authoring is mainly done in and using HTML (Hyper Text Markup Language), which is really quite a simple programming language that can (and often is) developed in a normal text writer
It is nor compiled, so everyone can see your code! That's actually quite amazing, because as good as it might be to expand knowledge (open source), is it also very open to copying by other people...... so you just have to flip a coin about the good and the bad of this approach
There are other programming languages that are more powerful than HTML, called XML, XHTML, ASP, and scripting languages like JScript, VBScript, etc..... but they are all basically open source..... who knows, maybe in time to come will systems become available that protect your web programs more from too easily copied.
There is another (good) reason why programming is so open..... it makes it a little bit more difficult for people to write programs that are destructive..... crash your computer, steel your informations, steel your money, etc.
Having created your web pages, and placed them on the web, is this a very powerful medium of communicating to the rest of the world, 24 hours a day, 7 days a week, every day of the year. People can simply access your website, and interact with your site.... that's actually quite something !
The only remaining thing to do is get people to find your site among the maze of millions of other sites..... this is done by advertising, or getting search engines to do it for you.....
WHICH PROGRAMMING LANGUAGE TO LEARN?
+ although you get many applications that will convert your WebPage into HTML, is this what the Internet / WWW is programmed in,
+ you dont need to buy a program to do this programming in and can use a simple Text Editor,
+ is it undoubtably the standard for at least the next 10 years.
- Once you have mastered these two lanaguages, will you be in a much better position to decide for yourself where to go from here.