Computer

What is a Computer?• A computer is a programmable machine. • A device that computes, especially a programmable electronic

machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information.

• A programmable machine that performs high-speed processing of numbers, as well as of text, graphics, symbols, and sound. All computers contain a central processing unit that interprets and executes instructions; input devices, such as a keyboard and a mouse, through which data and commands enter the computer; memory that enables the computer to store programs and data; and output devices, such as printers and display screens, that show the results after the computer has processed data.

Computer BasicsBasic Parts of a Desktop Computer

Introduction

The basic parts of a desktop computer are the computer case, monitor, keyboard, mouse, and

power cord. Each part plays an important role whenever you

use a computer.

Computer Case

The computer case is the metal and plastic box that contains the

main components of the computer. It houses the

motherboard, central processing unit (CPU), the power supply, and

more.

The system unit is the core of a computer system. Usually it's a rectangular box placed on or underneath your desk. Inside this box are many electronic components that process information.

MonitorThe monitor works with a video

card, located inside the computer case, to display images and text on

the screen. Newer monitors usually have LCD (liquid crystal display)

or LED (light-emitting diode) displays. These can be made very

thin, and they are often called flat panel displays. Older monitors

use CRT(cathode ray tube) displays. CRT monitors are much bigger and

heavier, and they take up more desk space.

LCD monitor CRT monitor

Power CordThe power cord is

the link between the power outletand the power supply

unit in the computer casing. If the power cord is not plugged in, the computer will not power on.

To protect your computer from voltage spikes, you can plug the

power cord into a surge protector. You can also use an Uninterruptable Power

Supply (UPS), which acts as a surge protector and also provides

temporary power if there is a blackout.

Keyboard

The keyboard is one of the primary ways we communicate with the computer and enter data.

How the keys are organized

• The keys on your keyboard can be divided into several groups based on function:

• Typing (alphanumeric) keys. These keys include the same letter, number, punctuation, and symbol keys found on a traditional typewriter.

• Control keys. These keys are used alone or in combination with other keys to perform certain actions. The most frequently used control keys are Ctrl, Alt, the Windows logo key , and Esc.

• Function keys. The function keys are used to perform specific tasks. They are labeled as F1, F2, F3, and so on, up to F12. The functionality of these keys differs from program to program.

• Navigation keys. These keys are used for moving around in documents or webpages and editing text. They include the arrow keys, Home, End, Page Up, Page Down, Delete, and Insert.

• Numeric keypad. The numeric keypad is handy for entering numbers quickly. The keys are grouped together in a block like a conventional calculator or adding machine.

• The following illustration shows how these keys are arranged on a typical keyboard. Your keyboard layout might be different.

Keys on the Keyboard

• Caps Lock Key The caps lock key activates a feature that affects only the letter keys. Pressing on the caps lock button causes all letter keys to type in uppercase. All other keys will act the same as if caps lock is off. To deactivate caps lock, press the caps lock key again.

• Shift Key The shift key is used in combination with a second key. The shift key is used primarily to capitalize letters. Shift differs from caps lock because you have to hold the shift key down while simultaneously pressing another key to capitalize a letter, where you only press the caps lock key once. Holding down the shift key also is used to type the characters and symbols above the numbers on the number keys.

• Tab Key• The tab key is used to move from one position on the screen to another. It also

creates a “tab stop” (right 1/2 inch) indentation for your paragraphs. This is very similar to a typewriter.

• Enter Key When working with text (words), pressing on the enter key moves the cursor down to the next line. Otherwise, pressing the enter key will activate anything that you have selected.

• Escape Key The escape key is used to cancel the current operation or can be used to exit a program.

Note: The Cursor is a blinking line when typing a letter that lets you know where you will start typing. (It moves as you type and looks like “|” )

• Space Bar Pressing the space bar while the cursor is positioned within text will cause a space (one character wide) to be placed at the position of the cursor (like on a typewriter).

• Control Key The control key (Ctrl) is usually used with another key. Holding the control key in addition to another key or keys will start a function. Later on, we will teach you some control key functions that deal with word processing.

• Alt Key The alternate key (Alt), similar to the control key, and is used in combination with other keys.

• Arrow Keys The four arrow keys are located on several keys to the right of the spacebar at the bottom of the keyboard. Pressing one of these keys will cause some type of screen movement in the direction of the arrow on the key. These keys are frequently used when correcting mistakes in documents and allow users to “go back” and fix mistakes instead of erasing all of the work since the mistake was made.

• Backspace Key Pressing the backspace key while the cursor is positioned within text will delete the character (or space) immediately to the left of the cursor.

• Delete Key Pressing the delete key while the cursor is positioned within text will delete the character (or space) immediately to the right of the cursor.

Mouse The mouse is a peripheral that is known as apointing device. It lets you point to objects on the screen, click on them, and move them.There are two main types of mice: optical and mechanical. The optical mouse uses an electronic eye to detect movement and is easier to clean. The mechanical mouse uses a rolling ball to detect movement. Generally, a mechanical mouse is cheaper, although it may require regular cleaning to keep it working properly.Traditionally, a mouse connects to the computer using a USB or PS/2 connection. However, you can also buy a wireless mouse, which can reduce clutter on your desktop.

Basic parts of a Mouse

• A mouse typically has two buttons: a primary button (usually the left button) and a secondary button (usually the right button). You will use the primary button most often. Most mice also include a scroll wheel between the buttons to help you scroll through documents and webpages more easily. On some mice, the scroll wheel can be pressed to act as a third button. Advanced mice might have additional buttons that can perform other functions.

Using the Mouse

Positions of hands on mice

Mouse Techniques

• Because the mouse is a critical component of the computer, we’ll examine some mouse techniques that will be used.

• The mouse can be used in many different ways. There are primarily the two mouse buttons, known as the left and right button. The left button is primarily used. Some mouse techniques include:

• Click: This is the easiest of the techniques, however it is very important that you do it properly. To click, you press down one of the mouse buttons. As you click it, it makes a “clicking” noise. The most important skill to learn when clicking is that it only takes a very light, short tap to click a mouse button. Don’t click the mouse too hard since this tends to slow you down. Once you have mastered clicking, you will be ready to move on to the next most essential practice, pointing.

• Left Clicking: This is the primary “click” that you will use. This is clicking on the left mouse button. When someone says, “click here,” that usually means to left click.

• Right Clicking: This is used to change options or perform specific functions that aren’t usually necessary for beginner.

• Point: Use the mouse to move the mouse pointer so that it hovers over the top of an icon or word on the screen. Sometimes, this is all that you need to do in order to prompt a response from the computer (as an example, the shape of your cursor may change).

Point and click: Move the mouse pointer over the top of an item (such as an icon) on your screen and then (while holding your hand still) gently press and release the left button on the mouse. This technique is often used to make a selection. Double-click: While hovering the mouse pointer over an item on the screen, quickly press the left mouse button two times. This may take some practice but it is a very useful and important skill. If you are having problems double clicking, it’s most likely because you’re moving the mouse slightly when double clicking. Try to steady your hand and try it again. By double clicking, you are usually prompting the computer to take an action on the item you selected (double clicking on an icon on your computer desktop may open or start a program). Click and drag: Press and hold down a mouse button (usually the left button). As you hold down the button, move the mouse in any direction. Click and drag is a method used when “highlighting” or “selecting” text. To do this to text, click at the beginning of the text that you want to select, hold down the left mouse button, and move your mouse to the end of where you want to highlight.

Other Peripheral

Devices

Printer

Inkjet printer (left); laser printer (right)

A printer transfers data from a computer onto paper. The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use.

Speakers

Speakers are used to play sound. They can be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.