Mouse

If you bought a pc in early 1980s, a keyboard would probably have been the only input device that came with it. today, all new PC, come with a pointing devices as standard equipment. If the computer is a desktop or tower model, the pointing device is usually a mouse. A mouse is an input device that rolls around on a flat surface and controls the pointer. The pointer is an on-screen object, usually an arrow, that is used t select  text; access menus; and interact  with programs, files, or data that appears on the screen.

            The mouse first gained widespread recognition when it was packaged with the Apple Macintosh computer  in 1984. Initially, some  users scoffed at this simple tool, but it  quickly became apparent that the mouse is convenient for certain types of input. For example, a mouse lets you position the cursor anywhere on the screen quickly and easily without having to use the cursor- movement keys. you simply move the pointer to the on-screen position you want, press the mouse button, and the cursor appears at the preselected position.

              The advantages of the mouse are so numerous that it changed the entire personal computing industry. Although the Macintosh operating system was the first widely available system to take advantage of the mouse , the tool's popularity grew rapidly. By the late 1980's. IBM - compatible PCs were quickly adopting the mouse as a secondary input device.

                   Instead of forcing you to type or issue commands from the keyboard, the mouse and mouse based operating system let you choose commands from easy to use menus and dialog boxes. The result is a much more intuitive way to use computers. Instead of remembering obscure command names, users can figure out where commands and options are located.

                      A mouse also allows you to create graphics such as lines, curves and freehand shapes, on the screen. with this new capability , the mouse helped establish the computer as a versatile tool for graphic designers, starting what has since become a revolution in the graphic design field.

The Standard Keyboard Layout

Keyboards for personal computers come in many styles. the various models differ in size, shape and feel, but except for a few special - purpose keys , most keyboards are laid out almost identically. Among IBM - compatible computers, the most common keyboard layout is the IBM Enhanced keyboard. It has 101 keys arranged in five groups as shown in the figure.The keyboard layout is close to the IBM Enhanced keyboard, but there are a few differences.

The Alphanumeric keys:
The alphanumeric keys - the parts of the keyboard that look like a typewriter - arrange the same way on almost every keyboard, Some times this common arrangement is called QWERTY layout because the first six keys on the top row of letters are Q,W,E,R,T and Y.
For decades, many expert typists have supported a different arrangement for alphanumeric keys called the DVORAK keyboard. This keyboard layout places the most commonly used letters in the middle row of keys, making them easier to reach. Special DVORAK keyboards are available for computer system but they are not standard equipment. A few keyboards manufacturers now offer keyboards that can be switched from QWERTY to DVORAK configurations.

Along with the keys that produce letters and numbers , the alphanumeric key group includes a few additional keys, with specific functions. these keys are similar to those found on a typewriter:

* Tab - The Tab key moves you to predefined tab stops in many application programs. In dialog boxes.you can press tab to move from one option or field to another.

* caps Lock  - As the name implies this key lets you "lock" the alphabet keys so they produce only capital letters. Caps lock does not affect the numeric keys or the keys that produce punctuation or special characters.

* Back Space - This key enables you to erase characters you have just typed for example in a word processing program you can press Backspace to "back over" an incorrect  character and delete it.

* Enter - The Enter key lets you finalize data entry in many types of the application programs . you can also use enter to choose commands and options in many programs and at various places in an operating systems interface.

The Modifier keys:


A keyboard's modifier keys are no named because they are used to modify the input of other keys. You press
another key while holding down one of the modifier keys are as follows:

* shift - A computers shift keys have the same function as a typewriters shift  keys; when pressed in conjunction with an alphanumeric key , shift forces the computer to output a capital letter or symbol. Shift also acts as a modifier key on some programs. In most word processors you can press shift along with various cursor movement keys to select text for editing.

* Ctrl - This key produces different results depending on the program you are using. In many windows based
programs, ctrl - key  combinations provide shortcuts for menu commands. For example , the crtl key combination  ctrl +o enables you to open a new file.

* Alt - this key called the alternative key operates like that control key.except that it produces different set of results. In windows based programs, Alt -key combination enable you to navigate menus and dialog boxes without using a mouse.

Standard methods of keyboard

Overview: Keyboard and the mouse:
If the CPU is the brain of the computer, then the input devices are its eyes and ears. From the users point of view, input devices are just as important as CPU - more so , in fact . After you have purchased and setup the computer, you can take the CPU for granted because you interact directly with the input devices and only indirectly with the CPU. Your ability to use input devices is critical to your overall success with the whole system.

An input device does exactly what its name suggests: it enables you to input information and commands into the computer. the most commonly used input  devices are the keyboard and mouse. In fact if you buy a new personal computer today it will include a keyword and mouse . It will include a keyboard and mouse unless you specify otherwise. As you will see, many other types of input devices are available, including variations of the mouse and specialized "alternative" input devices such as microphones and scanners.

the keyboard was one of the first peripherals to be used with computers and it is still the primary input device for entering text and numbers. A relatively simple device, a standard keyboard includes about 100keys, each of which sends a different signal to the CPU.

If you have not used a computer keyboard or type writer, you will learn quickly that you can use a computer much more effectively if you know how to type.the skill of typing or keyboarding, as it is often called today, implies the ability to enter text by using all ten fingers and without being able to type , and many people do. some people claim that when computers can understand hand writing and speech, typing will become unnecessary. But for now and the foreseeable future, keyboarding remains the most common way to enter text and other data into a computer

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Handheld personal computers

Since the mid 1990s, many new types of small personal computing devices have been introduced . and all fall under the category of  handheld personal computers. these tiny systems are also called palmtop computers, a handheld  Pc can be any sort of computer that fits in the user's hand, such as

1. Personal digital assistant
2. Cellular telephone with internet , email and fax capabilities.
3. H/PC Pro device

some of the handheld personal computers look like  mininotepad computers with small displays and keyboards, but are much smaller than even the tiniest full-featured notebook PC.This type of H/PC is sometimes called a mini - notebook computer. Most H/PC systems do not provide disks, but memory can be added  through PC cards or other means. software is abundant for these devices , most of which are internet - capable and can connect yo a full- size computer to exchange data.

Personal digital Assistants:

Personal digital assistants are among the smallest of portable computers, often they are no larger than a small appointment book, but they are much less powerful than notebook or desktop computers. PDAs are normally used for special applications, such as taking notes, displaying telephone numbers and addresses, and keeping track of dates or agendas. Many PDAs can be connected to larger computers to exchange data.

Most PDAs come with an electronic pen that lets the user write on a touch sensitive screen.
Even  though they do not include real keyboards, some of these devices provide a graphical keyboard  that appears on the screen . you type by tapping the desired keys with the units pen. Depending on the model, PDAs may include the following features:

1. Built in micro phone and speaker , enabling the user to record speech digitally.
2. Personal information management (PIM) software.
3. Miniaturized versions of personal productivity applications.
4. Internet , fax, or email software.

Cellular phones

Some new cellular phones are doubling as miniature PCs. advanced cellular devices combine analog and digital cell phone service with email capabilities. Such phones enable the user to check and send email and faxes over the phone. they offer features not normally found on a phone, such as personal organizers or access to the web. Some models even break in half to reveal a miniature keyboard.

H/PC Devices:

Probably the most curious new development in handheld technology is the  H?PC Pro family of devices. these systems are larger than PDAs or  miniature notebooks, but they are not quite as large as typical notebook PCs, with features some where between the two. for  example , H/PC Pro systems boast nearly full sized keyboards and color displays . they can run more types of miniaturized applications than their smaller counterparts, but those applications still do not provide the features of normal desktop software. H/PC Pro units offer long battery life and instant - on access but they  do not include disks. although they will gain speed and storage capacity quickly, H/ PC Pro systems offer very limited RAM and relatively slow processor speeds.

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Network computers

In some situations user does not need all the power and features provided by personal computer. If you want to use only the internet, for example  or if your job involves data entry, then you may need the processing power , memory, and storage capacity of a fully equipped PC. In this instance a network computer becomes useful.

A network computer is a less powerful version of a personal computer, with minimal processing power, memory and storage. Network computers are designed to be connected to a network , a corporate intranet, or to the internet. The NC relies on the network for software and data storage and may even use the network's server to perform some processing tasks.

In the mid 1990s, the concept of network computers became popular among some PC manufacturers, who pronounced the NC as the future of computing. However, no single NC standard emerged as various hardware and software makers fought to command this new market. As a result , several variations on the network  computer quickly became available and consumers almost immediately became confused about their differences and special purposes. while network computers have gained some market share in business, they have not succeeded to the extent their makers anticipated.

In business, variations of the network computer are thin clients, diskless workstations, windows terminals and Net PCs. Some network computers are designed to be connected only to the Internet boxes, Internet appliances, or step - top boxes. In home settings, some network computers do not even include a monitor; instead, they connect to the user television , which serves as the out put device.

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Notebook computers or laptop computers

Notebook computers , as their name implies approximate the shape of an 8.5 by 11 inch notebook and can fit inside a briefcase easily. Also called  Laptop computers, they can operate in alternating  current or special batteries.Notebooks are fully functional microcomputers; the people who use them need the power of a full - size PC wherever they go.

Some notebook systems are designed to be plugged into a docking station which may include a large monitor, a full-size keyboard and mouse, or other devices such as an additional hard drive or backup tape unit. Docking stations also provide additional ports that enable the notebook computers to be connected to different devices in the same manner as desktop system. Some expansion bases also feature built in networking curds so one is not required in the notebook computers.

Because of their size , notebook computers often feature a smaller display, less memory and less storage space than a full size PCs. Also because their size, notebook computers tend to be more expensive than computers. Depending on its features, a fully equipped notebook computer can cost between $500 and $5000.

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Desktop Models

The First style of personal computer introduced was the desktop model. In common usage , the term desktop system means a full size computer that is small enough to be used at a desk but too big to carry around. Traditionally a desktop computer's main case is horizontally oriented, meaning it can lie flat on a desk or table.

A variation of the desktop system is the tower model. where the system unit sits vertically and has more vertically and has more space for devices. Because of its design, the system unit is often placed in the floor to preserve desk space, allowing more room to place external components, such as removable disk drives or scanners, on the desktop.

Tower models have become increasingly popular in recent years - so much so that some PC makers have stopped offering horizontally oriented desktop system.

Personal computers can cost anywhere from $600 to $7500, depending on the capabilities and capacity. The most popular models cost between $1000 and $3000. The tremendous growth and potenial of the pc market has brought many manufactures into this arena.

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