Basics of Computer
1. What computers are and are not
The term 'computer' is misleading for many people. It suggests that these machines are mainly about computing with numbers; that was their original use, but they are in fact 'all-purpose' machines. A computer can work as a telephone, a television, a VCR, a CD player, a typewriter, a bulletin board, a post office, a multimedia textbook, a mini-library, an art gallery, a music-composing tool, etc. You can use it to design a house, create a 3D painting, simulate a science experiment, and, yes, even compute with numbers. Most uses of computers in education today do not involve numbers at all.
2. How a computer works
The brain of the computer is called the Central Processing Unit (CPU). It is located inside the main box on a printed electric circuit called a Motherboard; it is a 'micro-chip', a piece of ceramic-like material that has billions of microscopic electrical connections etched onto it. Any form of information (words, pictures, sounds, numbers) can be converted to electric signals that are 'input' to the chip. The electric connections on the chip allow these signals to be compared to one another and combined with one another according to a 'program' that 'processes' or manipulates the information into a new form, which becomes the 'output' electric signal from the chip. Everything else in a computer is designed to take human information and convert it to the input electric signals for the chip, or to take the chip's output signals and convert them back to a form that humans can recognize. These other components are called 'peripherals', or just input and output devices.
3. Computer programs
Something has to tell the chip what to do with each input signal in order to combine it with other input signals to make the output: the program. The program is just more information; it is written in a 'programming language' that is a cross between English and Algebra. An input device called an 'interpreter' or 'compiler' converts the typed program into input signals to the chip. The chip combines the other input information with the program information to create its output signals. All information for the chip has to be in the form of a simple electric signal: voltage on (or voltage high) vs. voltage off (or voltage low). This simple signal is represented by a '1' (for ON or High) vs. a '0' (for OFF or Low) in writing programs. Every letter of the alphabet, every number, every color, every location on the computer screen, every sound has a code in terms of a long sequence of 1's and 0's (voltage signals), such as: 100111010100011101.
Since this form of coding is slow and hard to remember, programming languages are built so that the program writer puts in words and special symbols (for operations like comparing two codes, storing a code temporarily in the computer's memory chip, etc.), and the language runs its own program to convert these into the actual 1 and 0 codes. As computer languages have become more advanced they have basically become complex programs themselves: they tell the CPU how to convert instructions from the user into 1 and 0 codes. A long set of instructions makes up a program, and is also called 'the code' for that program. The 1's and 0's are called the 'machine language code' -- since they directly control the electric signals to the chip -- and the instructions about what to do with each unit of information is called the 'assembly language code'. Most programmers write in a 'high level language' (e.g. C++ or Visual Basic or Java), which runs a little program to convert itself into the machine code. In high level languages the kinds of instructions you write are things like: Open a window on the screen, take the words from this file and display them in the window, highlight the word that the mouse cursor (see below) is over, etc.
4. The parts of the computer
What you see when you look at a typical computer workstation is:
- a Monitor -- looks like and basically is a TV screen and controls
- a Keyboard -- like a typewriter but with many useful extra keys
- a Mouse -- a palm-size gadget that rolls on a ball and has buttons on it
- a Printer -- inkjet or laser-xerox miniature printing machine a microphone and speakers -- if you're lucky, not all machine have these
- a pair of stereo Speakers, for multimedia systems (also sometimes a Microphone to speak into)
- a miniature TV camera -- if you're very lucky; not yet common
- the BOX -- contains the CPU microchip and all the really important components
So then, what's in/on the BOX?
On the Front of the box:
- On/Off switch (sometimes on the side)
- Reset button -- only on some machines
- Floppy-disk Drive -- you put in a square disk that contains information
- CD-ROM drive -- you put in a digital CD platter that contains a lot of information
- Tape Drive -- optional, for storing information in case something goes wrong
- Other special drives -- old-fashioned big diskette drive, super-new storage drives
- On/off light, Hard Disk Operating light, miscellaneous lights and buttons
Inside the Box. What you see on the front is just the opening slot of the actual drives. A 'drive' is a storage device. In addition to the CPU chip and the input and output devices, computers need places to store information either temporarily or more permanently (for reuse later), the short-term storage is called RAM (random-access memory) and is expensive. For longterm storage various kinds of disks and platters and cassettes are used; these are basically like videotape, but much higher quality, or like CDs. The drives read the information off these storage media and pass it on to the CPU; some drives can also write new information onto the disk or platter/CD or cassette.
- The CPU and RAM memory chips on the 'motherboard'
- The HARD DRIVE -- the main longterm storage system for programs and info
- The Disk and CD-ROM drives -- the main part of them is inside the box
- The specialized 'Boards' -- these run the input and output devices
- The Modem -- one of the boards; connects to the telephone line
- Network Board -- another board, connects to the LAN (see below)
- Video Board -- connects to the monitor
- An electic power supply, battery, and a lot of connecting cables
Every input device and output device is connected first to a specialized Board that has its own microchip to convert signals and pass them on to the CPU (on the main or Mother Board).
On the back of the Box. This is where all the input/output peripherals are connected to the Box, and the Box is connected to the electric outlet, the telephone system (for a modem), and the local area computer network (LAN) cable system. There are a lot of confusing cables back here. Sometimes they come lose. The specialized Boards stick out the back slightly, just like the drives stick out the front slightly. The Boards have connector sockets called Ports where the keyboard, mouse, printer, monitor, etc. are supposed to be plugged in.
5. How to turn it on
To make the computer work, there has to be electric power to several different parts, so there are sometimes several ON switches; you need to turn ALL of them on. If you are lucky there will be one Master Switch to do all this for you, but don't count on it. First make sure there are no disks VISIBLE in any of the drives (look, don't touch). If there is one in the drive, push the release button to get it out. Now, turn on the power supply switch if there is one (sometimes called Master Switch). Turn on the Monitor (watch for a light to come on). Turn on the Printer (optional). Turn on the Box.
The machine is working if: lights come on on all the parts, after a minute or less you see something on the monitor screen: words, numbers, changing colors. It takes a few minutes for a computer to warm up and get itself ready to work, be patient.
6. The 'Boot Up' Process
Watch the monitor screen while the machine is starting up. It may go by fast at times, but you can learn a lot. There are ways to slow it down, too, but that's for advanced users. The first things you usually see on a PC (not a Mac) is the count-up of the RAM memory. 8000 is very small, 16000 is ok, 32000 is good, more is wonderful. The machine is really testing the short-term memory storage to see that it's working and how much there is. You can add more memory by paying for it and sticking it in the box.
Now the machine starts to check all the different input and output devices. It looks for the keyboard and tests it, the mouse, the monitor, the printer, the hard drive, the disk drive, the CD-ROM drive, etc. For each of these it loads a program called a 'driver' program to convert signals between the CPU and the device. This is the time when the machine detects any problems. Hope that it doesn't find anything wrong! This is also usually the time when a program is run automatically to check for 'viruses' (these are unwanted programs that can damage the machine or make it not work properly; they have nothing to do with biological viruses at all).
If everything is working, the machine displays the USER INTERFACE. This is your signal that you can now take over and tell the machine what to do. Everything before this was automatic, run by programs built into the machine. The basic startup program is called the BIOS, then there are other programs that you can sometimes change (like how to check for viruses, what kind of CR-ROM drive you have, etc.).
7. The Operating System and the User Interface
The operating system is the master program that runs the computer behind the scenes while you work. It translates your instructions into actions by the machine. It also heads off conflicts between one part of the machine and another, making them all take turns. The most common operating systems are Windows, MacOS, and Unix. DOS is an older system that is now a small part of Windows.
The User Interface is what you see on the screen at the beginning. You can come back to this screen anytime you need it. Sometimes a part of it is always visible. The simplest user interface is a Command Line. The line is shown by a Prompt, some symbols that tell you where to type your commands (e.g. C:\windows> ...); this is not so common today, but it is easy to use -- if you remember the Commands. Since most people can't remember a lot of commands or don't want to be bothered, the alternative is a GUI, graphical user interface: a pretty set of little pictures called 'icons' with printed labels on them that appear on the screen to remind you of the commands. The Mouse is used to 'click' on an icon or label to issue a command. The most common commands are the ones to start new programs. The programs then give you more choices of specialized commands to edit text, draw pictures, access the internet, etc.
8. Programs, Commands, Folders and Files
An 'application program' is the most common kind of program. A word-processor is an application program for writing, reading, and editing text. A paint or draw program is for making, viewing, and changing pictures. A calculator program is for doing arithmetic. Almost everything you want to do with a computer is available, for a price, as a program or set of connected programs. Every program appears on screen as an icon, or has a command to start it.
Once you start a program, there are special commands that work only in that program to make it do things, or there are special icons that appear to help you do these things. Many programs have a linked Help program, that tells you what to do. Some have Wizard programs that walk you step by step through something. There are also Tutorial programs to introduce a new program to you. And there are program manuals, printed books that explain how to use the program. To use any program you have to LEARN how.
Most programs create, read, and modify information. This information is then stored in a FILE. There are text files, picture files, sound files, video files, multimedia files, and others. All information in a computer is stored in some kind of a file. To keep track of all these files, there is a Filing System, a special program built into the operating system. What you see are Folders (also called directories or subdirectories), and inside a folder there are files. There can also be folders inside other folders. To locate a particular file of information, the computer, and sometimes you, need to know the Path to the file, which consists of telling what DRIVE it is stored on, what folder it is in, what folder that folder is in, and so on. Usually each drive has a letter, or an icon. If there are letters, A: and B: are the floppy disk drives, C: is the main hard disk drive (where most of the files are kept permanently), and other letters can be other disk drives and CD-ROM drives. A path might look like C:\windows\system\audio.dll -- this is the path to a file called audio.dll that contains information that the windows operating system uses to communicate with the speakers and play music or sound; it is in a folder called System and that is in a folder called Windows and that folder is permanently stored on the C: hard drive. Usually you can just use the icons for the file system to click on folders, 'open' them, and see more folders or files 'inside' them. These are just visual images on the screen, not the actual files, but you can link to the real files by clicking on their image icons.
10. Actually doing something
Start up the computer (section 5). Wait till everything stops. Click on an icon on the user interface screen. If nothing happens, 'double click' (twice very fast) or hit the Enter key. This will either start a program or open a folder than contains files and programs. On many computers if you double-click a file that can be seen or heard with a program, the program will automatically start up and show the file (a text, a picture, etc.). Otherwise you have to start the program first and then use its special commands to open a particular file.
Look for a MENU bar at the top of the screen once a program has started. Move the mouse around to put the cursor on the menu bar and press the button on the mouse. You should see a list of commands. Click on a command, or move the mouse with the button held down over a command and then let go of the mouse button (takes a little practice). If there is a FILE menu of commands, one will be the OPEN command. If you activate this command, a little box will usually appear to ask which file you want to open, and very often there will be a way to see a list of all the files that the program can use. There will also be a NEW command, to let you create a new file, e.g. a new text document, a new picture, etc.
There is also usually a HELP command somewhere near the end of the MENU bar, or pressing the F1 key (one special key, not F and 1) may start the Help program.
The FILE menu will also usually have a QUIT or EXIT or CLOSE or STOP command which will either close the file you are using or stop the program altogether (it does not stop the computer, just one program). The program will usually ask you if you want to save the new file or changes you made to a file in permanent storage. If it was a new file, say YES; if it was a file you found already in the computer, say NO, unless you are really sure that it is ok to make a change in it. A file remains unchanged in storage unless you specifically SAVE changes to it. The copy on file is not the copy you see on the screen, until you tell the machine to replace the file copy with the one on screen. This is called SAVING the new file.
The operating system usually knows what program goes with what file (this is called an 'association'), but sometimes you have to tell it. Sometimes a program cannot use a file of information until it has been 'converted' to work with that program. If you have a paper you wrote on a Mac and want to print it on a PC, it has to be converted first. If you have a paper you wrote with the MSWord program and you want to edit it with the WordPerfect program, it has to be converted first. Always keep a copy of the original version, just in case something goes wrong. This safety rule is called 'backing up' the file, i.e. keeping a spare copy of the old version in case the new version doesn't work or is accidentally lost or ruined.
Key Things to Learn First:
How to use the Mouse to start a program and use menu commands in a program How to copy a file from a disk to the hard drive and vice versa How to make a back-up copy of a file on a disk or on the hard drive How to find a program or a file in the computer's filing systems of folder icons How to check a disk to make sure it has no viruses on it (VERY IMPORTANT!!) How to start a Browser program to access the Internet (WWW, web) How to print a file How to store on disk or hard-drive a copy of a file you found on the internet
The Most Important Types of Application Programs
- Word Processor -- creates, reads, edits text files; sometimes can add pictures or tables
- Paint or Draw -- creates, shows, and changes pictures and images; usually in color
- Database -- stores and organizes information, helps locate needed information
- Spreadsheet -- does simple math calculations, especially for businesses
- Communications -- helps connect to other computers by modem and telephone
- Browser -- connects to the Internet to show web pages
- Email -- write, read, send, receive, store, and organize electronic mail messages
Input Devices: Keyboard, Mouse, Microphone, Trackball, Joystick; Disk or CD drive when it reads a disk or CD Output Devices: Monitor, Printer, Speakers; Disk drive when it writes information onto a disk Storage Devices: Hard disk, Floppy diskette disk, CD-ROM platter disk, Tape Backup drive
Types of Computers: Macintosh, Windows PC, Unix workstation, Mainframe, Supercomputer
Communications between computers: Modem -- telephone connection; LAN -- local cables; Internet -- long-distance cables
