Welcome to Computer Basics

Computers are wonderful tools that enable us to do many different tasks.  This site is designed to help you understand some basic terminology and the basics of how computers work.

Lesson 1   - What is a Computer?
Lesson 2   - Hardware & Software
Lesson 3   - Basic Computer Parts
Lesson 4   - How does it Work?
Lesson 5   - Measuring Space
Lesson 6   - What’s Inside?
Lesson 7   - Peripheral Hardware 
Lesson 8   - Understanding the Keys
Lesson 9   - Memory
Lesson 10 - Processing  The CPU
Lesson 11 – Storage

Easy Printout version

J. Callahan

Berkeley Preparatory School

Updated August 2000

 
 

What is a computer?

A computer is an electronic machine that stores and manipulates information (data).  It does this by following specific instructions.  These instructions are called programs or software.  It can process and store large amounts of data very quickly.  A computer seems to be able to do lots more than this.  You may see pictures, text, or video and hear sound, but all the computer sees is numbers.  If you wanted to give the computer specific instructions to follow, you’d have to write a program for it to follow.  These programs are written in one of many computer languages such as C++, Visual Basic or HTML.  Someone who writes programs is called a programmer.

Computers come in many sizes and shapes and are used to do many different tasks.  A computer system as we know it is a personal computer (PC), but special purpose computers exist in many places.  If an item contains a microchip, it is computerized.  If you use a calculator, ATM, microwave oven or VCR, you’re using a computer of sorts.

What can you do with a PC?  Use a word processing program to write a report, use a drawing program to create pictures, use e-mail software to send a message to a friend across the globe, use an Internet browser to display a web page, or just play a game.  ( Back to Menu)

Hardware & Software

Computers require both hardware and software in order to work.
Hardware
Hardware is the physical parts of the computer like the monitor, keyboard, mouse, speakers, and of course the computer itself called the system unit.  Hardware is also the parts inside the system unit that you can’t see unless you open it up.  Parts like the motherboard, expansion cards, and modem.  Many hardware devices can be attached to a system unit to expand its capabilities, such as a speaker, scanner or printer.

Software
Software is the instructions given to the computer that tells it what to do.  A computer cannot do anything without instructions.  A computer must first read instructions before it can start to work.  These instructions are called operating system software.  When a computer is turned on, the first thing it does is find and read its system software.  This software tells the computer how to work; how to be a computer.  Once a computer has done this and is “booted up” or ready to go, it can read other instructions called application software.  This type of software tells the computer how to do a specific task with a user, like writing a report, playing a game, or creating a graph.  ( Back to Menu)

Basic Computer Parts

There are 4 basic types of computer parts:

1. Input devices - parts of the computer that allow information or data to be given to the computer like keyboard or a mouse.

2. Storage devices – parts of the computer that hold information.  The primary storage device is the computer’s memory called RAM (random access memory).  It remembers everything that is read, input, or output.  But, because the computer’s memory is on a temporary area—it forgets everything when turned off—it must have another place to store information permanently.  This secondary storage device is usually a disk.

3. Processing device – part of the computer that processes and controls the flow of information; it actually does the work.  The one part of the computer that handles this job is the central processing unit or CPU.

4. Output devices - parts of the computer that give out information generated by the computer, like a monitor, printer or speaker.

A typical computer system will have the following standard parts:  system unit, monitor, printer, keyboard, mouse, speakers, modem, hard drive, floppy drive, CD-ROM drive.

Can you determine whether the computer parts listed below are input devices, output devices or storage devices?

( Back to Menu)

How does a computer work?

Computer process information or data, which can be in the form of numbers, letters, words, pictures or sounds.  It carries out four activities to do this.  This is called the information processing cycle because it does these activities over and over and over.

Imagine typing your name.  As you press each key, you are inputting new information.  The computer remembers what you typed in its memory.  It processes the input and decides how the letter should look and where it should be placed.  It then displays each letter on the monitor screen.

Imagine printing a document.  You click on the commands with your mouse (input).  The computer remembers what you did (memory) and processes (CPU) the information by deciding what to do and where to send the information.  It then prints the document (output).

Everything little step you take while working with your computer requires all these tasks to take place.  They happen very quickly and happen over and over again in a cycle. ( Back to Menu)

Measuring Space

Just as you measure your height in inches and your weight in pounds, a unit is needed to measure memory and storage space.

One byte is the space needed for one character (number, letter or symbol of the keyboard).  One byte is made up of eight bits—the smallest unit of information a computer can process.

Because reports we write or pictures we draw take much more space than one byte or even 100 bytes, we see very large numbers related to computer storage:

Kilobyte (K) – 1,024 (about 1,000) characters or about one page of double-spaced text.

Megabyte (MB) – 1,048,576 (about a million) characters or about one book.

Gigabyte (GB) – 1,073,741,824 (about a billion) characters or about a whole shelf of books in a library.

Terabyte (TB) – 1,099,511,627,776 (about a trillion) characters or an entire library of books.

What do you find inside the computer?

Inside the computer you’ll find a motherboard on which everything is attached.  There are slots called expansion slots on the motherboard.  Expansion cards are inserted into these slots allowing other parts to communicate.  A monitor, mouse and keyboard, for example are attached to cards inside the computer.  The connection is made by plugging the device into a port (opening) that sticks out the back of the computer case.  If you were to see inside, you’d see the card on the other side of the port.  If you want to add sound to your computer, you’d purchase a sound card to add to an empty slot on the motherboard and speakers would plug into the port that shows out the back of the case.  A modem is also a card inside to which a phone line can be attached.

Also on the motherboard, we’d find a group of microchips, which are the RAM, or memory of the computer.  We’d also find a rather large chip that is the central processing unit or the brain of the computer.

Because the computer’s memory is only a temporary area, inside we’d find different types of drives for disks to hold information permanently:  the floppy drive, the CD-ROM drive and the hard drive.

We’d also find a power supply enabling the computer to use electricity and a fan to keep the inside from over heating.
( Back to Menu)

Peripheral Hardware

The mouse is a basic device that allows a user to use a point and click method of inputting information to the computer.  It usually has two buttons, left and right. Some have a wheel for scrolling. Mouse actions are the click, the double-click, the right-click, and the drag and drop. A mouse pad provides a good surface for the mouse.  Other pointing devices are the cordless mouse, a joystick, a touch pad and a trackball.

The keyboard is another input device allowing for entering and deleting of text, numbers and symbols as well as moving around on the screen and providing shortcuts.  See the keyboard page for information on each key.

Printers – get this from previously saved sheet

The monitor provides basic output for a user to see and interact with the computer.   It plugs into a port on the back of the computer which is a video card inside.  Monitors come in different sizes and are measured diagonally across the screen as televisions are.  Newer flat screen monitors are called LCD (liquid crystal display) panels.  Monitors will provide controls to change the image just like a television.  Many have the capability of being tilted and turned to adjust for the users comfort.  In the past, if an image were left on the screen for a long time, it would permanently burn into the screen.  Screen-savers (moving images) were developed to guard against this problem.  Many monitors have an energy saving device built in that puts them into a sleep mode.  When not used for a certain period of time, the screen goes black, but is brought back for use by pressing a key or moving the mouse.

Resolution and dot pitch pixels?

Speakers (output) and microphones (input) can also be added to a computer to give sound capability.  They would be plugged into ports on the back, which is actually a sound card inside the computer.   Other devices such as a CD-player, amplifier or musical keyboard can also be added.

The modem is a device that allows the computer to use a phone line so it can send or receiver information (data) from a computer elsewhere, in other words, talks to another computer.  It is usually found inside the computer as a card that supplies a port for the phone line to connect.  It can, however, be an external device found outside the system unit.

Since the phone was invented to carry analog information (sound), but the computer generates digital information, the modem actually acts as a translator.   It translates digital to analog (modulate) when being sent and translates back from analog to digital (demodulate) when being received.  The combination of mo and dem for its name modem.  The speed at which a modem can translate and send information is probably its most important feature.  You want one that will work fast!  A typical modem will handle 56,000 bits of information in one second or 56 bps.  This is called its baud rate.  Other ways of sending information have more recently been developed, such as cable.  Many of you probably have Roadrunner.  This service allows the computer to send information in a different way, which is much faster, and it doesn’t tie up your phone line.   Obviously, if the computer is using the phone, someone else cannot.

Given the ability to communicate through phone lines, a computer can now help us send e-mail and use the Internet.

A scanner is a device that your computer can use to turn a picture or text page into a computer file.  This is a neat way to add a photograph or picture you drew into a document you’re creating.  If you have a paper you printed but now need to edit and you can’t seem to find the file, a scanner with optical character recognition (OCR) can read it and turn it back into a computer file for you and save you from typing it all over again.

There are many types of scanners, ranging from a small handheld type to a large flatbed type.  Each can handle different size pictures or documents, the larger being the most expensive to purchase.

Another way to get photographs into you documents is by using a digital camera.  Some use removable disks or memory cards to store photographs, while others have a built-in memory that holds a certain number of photos.  Once the memory is full, however, you’d have to transfer them out or erase them to get space for more photographs. ( Back to Menu)

Understanding the Computer Keyboard

Escape - Used to quit a task or remove a dialogue box from your screen. “Let me out of here.”

Tab - Used to jump in to a particular place on the writing line, usually set for paragraph indents, but may be changed for other purposes.

Shift - Used to make capital letters or the upper character of a two-character key.

Caps Lock - Used to change the case of all letters to uppercase.  (If on, the shift key will shift to lowercase.)  Only works with alphabetic keys.

Ctrl and Alt - Used in combination with another key to perform a specific task, for example:  Ctrl+C is used for the command Copy.

Spacebar - Used to insert a blank space.

Enter - Used to tell the computer to carry out a task.  In word processing it’s used to start a new paragraph.

Function Keys - Used to perform specify tasks, for example, F1 displays the help information.

Backspace - Erases the character to the left of the cursor.

Delete - Erases the character to the right of the cursor.

Insert - Toggles between Insert and Overwrite mode.

Cursor Control Keys:
Arrows - move the cursor in the direction chosen.
Page Up - Brings the cursor up several lines (one screen, not one page).
Page Down - Brings the cursor down several lines (one screen, not one page).
Home - Brings the cursor the to beginning of the current line.
End - Brings the cursor to the end of the current line.
Ctrl + Home - Brings the cursor to the beginning of the document.
Ctrl + End - Brings the cursor to the end of the document.

*Numeric keypad - When the Num Lock is ON, the keypad is used like a calculator.  When OFF, the keys become a second set of cursor control keys.

*Status lights let you know if Num Lock and Caps Lock are on or off.

Test yourself here on the keyboard
( Back to Menu)

Memory 

The computer’s memory or RAM  (random access memory) is a temporary area with space limitations.  It’s an area that is constantly changing.  Like a blackboard it contains information for a while, is erased and is then replaced by other information.  As you’ve already learned, the space of a computer’s memory is measured in bytes.  A computer needs lots of space to hold programs the computer has read and is currently using like its operating software and application software.  You might have several programs open and running at one time.  This is called multi-tasking. The computer has to remember all of these instructions in order to do its work. New information you input into the computer is also held in its memory, like reports being written, games as they’re being played, or graphics that are being created.

A computer’s memory is usually about 32 or 64 MB (megabytes) is size, though they can be larger.  You definitely want a computer with the capability of have more memory added enabling you to upgrade in the future.  Computers with small memories will have limitations.  They won’t be able to handle multi-tasking or running large memory-intensive programs.  You will get an "out of memory" message.  Yes, a computer's memory can get filled.

RAM is really a computer chip, or a series of chips (single in-line memory module or SIMM).  One can add more memory to their computer by purchasing and inserting this small circuit board that holds memory chips into a special memory module socket on the motherboard.

Memory, as already mentioned, is a temporary area; what you put there is only ther for a while.  When the computer is turned off, the memory is erased.  When a computer is turned on, the first thing it does is read its system software and put it in RAM.  As you click on an icon to start a program, it reads all the needed instructions and puts them in RAM.  As you write a report with your word processing software, the report is entered into RAM.  What would happen if the power failed at this point in time?  Everything in memory would be lost.  To start up again, the computer would have to read the system software, read the word processing software and since your report was lost, you’d have to write it all over again.  If you were smart, you would save the report as you worked on it.  Where would it be saved?  It would be written on a disk of some sort, whether a floppy or hard disk.  (See storage lesson.)  Where is the system software already saved?  Where is the application software already saved?  On some type of a disk, usually the hard disk inside the computer.  This is where the computer would look to find a program it needs to read or some data you have created and saved.  So, as you can see, the memory is constantly changing.  Each time you start a program, open a saved file, or input new information, the memory contains this information.  When these files or programs are closed, they disappear from memory. ( Back to Menu)

Processing  The CPU 

The central processing unit (CPU) is the brain of the computer.  It is a computer chip found on the motherboard that carries out instructions, directs the flow of information through the system, and makes calculations.  It works very quickly carrying out millions of instructions each second.  It is a very complex computer chip.  Manufacturers are continually improving CPUs to be more powerful and faster.  Just as there are different makes of cars and other products, there are different manufactures of computer chips such as Intel, MD and Cyrix.   are improved, each generation is more powerful than those. ( Back to Menu)

 

 J. Callahan

Berkeley Preparatory School

Updated August 2000