One of the most basic system components is the keyboard, which is the primary input device. It is used for entering commands and data into the system. In the years since the introduction of the original IBM PC, IBM has created three keyboard designs for PC systems, and Microsoft has augmented one of them.

These designs have become de facto standards in the industry and are shared by virtually all PC manufacturers. The primary keyboard types are as follows:

• 101-key Enhanced keyboard

• 104-key Windows keyboard

• 83-key PC and XT keyboard (obsolete)

• 84-key AT keyboard (obsolete)

This section discusses the 101-key Enhanced keyboard and the 104-key Windows keyboard, showing the layout and physical appearance of both. Although you can still find old systems that use the 83-key and 84-key designs, these are rare today. Because all new systems today use the 101- or 104-key keyboard design, these versions are covered here.

Enhanced 101-Key (or 102-Key) Keyboard

In 1986, IBM introduced the "corporate" Enhanced 101-key keyboard for the newer XT and AT models. I use the word corporate because this unit first appeared in IBM's RT PC, which was a RISC (reduced instruction set computer) system designed for scientific and engineering applications.

Keyboards with this design were soon supplied with virtually every type of system and terminal IBM sold. Other companies quickly copied this design, which became the standard on Intel-based PC systems until the introduction of the 104-key Windows keyboard in 1995.

The layout of this universal keyboard was improved over that of the 84-key unit, with perhaps the exception of the Enter key, which reverted to a smaller size. The 101-key Enhanced keyboard was designed to conform to international regulations and specifications for keyboards.

In fact, other companies such as Digital Equipment Corporation (DEC) and Texas Instruments (TI) had already been using designs similar to the IBM 101-key unit. The IBM 101-key units originally came in versions with and without the status-indicator LEDs, depending on whether the unit was sold with an XT or AT system.

Now many other variations are available from which to choose, including some with integrated pointing devices, such as the IBM TrackPoint II pointing stick, trackballs and touch pads, and programmable keys useful for automating routine tasks.

The Enhanced keyboard is available in several variations, but all are basically the same electrically and all can be interchanged. IBM—with its Lexmark keyboard and printer spinoff—and Unicomp (which now produces these keyboards) have produced a number of keyboard models, including versions with built-in pointing devices and new ergonomic layouts.

With the replacement of the Baby-AT motherboard and its five-pin DIN (an acronym for Deutsche Industrie Norm) keyboard connector by ATX motherboards, which use the six-pin mini-DIN keyboard connector, virtually all keyboards on the market today come with cables for the six-pin mini-DIN connector introduced on the IBM PS/2s.

Although the connectors might be physically different, the keyboards are not, and you can either interchange the cables or use a cable adapter to plug one type into the other; some keyboards you can buy at retail include the adapter in the package. Many keyboards now include both the standard mini-DIN as well as USB connectors for maximum flexibility when attaching to newer systems.

104-Key Keyboard

With the introduction of Windows 95, a modified version of the standard 101-key design (created by Microsoft) appeared, called the 104-key Windows keyboard. If you are a touch typist as I am, you probably really hate to take your hands off the keyboard to use a mouse.

Windows 9x and newer versions make this even more of a problem because they use both the right and left mouse buttons (the right button is used to open shortcut menus). Many new keyboards, especially those in portable computers, include a variation of the IBM TrackPoint or the Cirque GlidePoint pointing devices, which enable touch typists to keep their hands on the keyboard even while moving the pointer.

However, another alternative is available that can help. When Microsoft released Windows 95, it also introduced the Microsoft Natural Keyboard, which implemented a revised keyboard specification that added three new Windows-specific keys to the keyboard.

The Microsoft Windows keyboard specification, which has since become a de facto industry standard for keyboard layouts, outlines a set of additional keys and key combinations. The 104-key layout includes left and right Windows keys and an Application key.

These keys are used for operating system and application-level keyboard combinations, similar to the existing Ctrl and Alt combinations.

You don't need the new keys to use Windows, but software vendors are adding specific functions to their Windows products that use the new Application key (which provides the same functionality as clicking the right mouse button).

The recommended Windows keyboard layout calls for the Left and Right Windows keys (called WIN keys) to flank the Alt keys on each side of the spacebar, as well as an Application key on the right of the Right Windows key. Note that the exact placement of these keys is up to the keyboard designer, so variations exist from keyboard to keyboard.

USB Keyboards

Most keyboards now on the market can connect to the PC via a USB port instead of the standard PS/2 keyboard port. Because USB is a universal bus that uses a hub to enable multiple devices to connect to a single port, a single USB port in a system can replace the standard serial and parallel ports as well as the keyboard and mouse ports.

Most current systems and motherboards still include the standard ports (now called legacy ports) as well as USB, but most so-called legacy-free systems and replacement motherboards have only USB ports for interfacing external devices.

Most keyboard manufacturers now market USB keyboards, but if you want to use your keyboard with both legacy (PS/2) and legacy-free (USB) systems, the most economic way to do so is to specify a keyboard that includes both a USB connector and an adapter to permit the keyboard to work with PS/2 ports.

Although Microsoft's Natural Keyboard Elite was the first widely available model to offer USB and PS/2 compatibility, other wired and wireless models from Microsoft, Logitech, Belkin, and others now offer this feature. You can also purchase third-party USB-to-PS/2 adapters, but these can be expensive and might not work with all keyboards.

Not all systems accept USB keyboards, even those with USB ports, because the standard PC BIOS has a keyboard driver that expects a standard keyboard port interface to be present. When a USB keyboard is installed on a system that lacks USB keyboard support, the system can't use it because no driver exists in the BIOS to make it work.

In fact, some systems see the lack of a standard keyboard as an error and halt the boot process until one is installed. To use a keyboard connected via the USB port, you must meet three requirements:

• Have a USB port in the system

• Run Microsoft Windows 98, Windows Me, Windows 2000, or Windows XP (all of which include USB keyboard drivers)

• Have a system chipset and BIOS that feature USB Legacy support

USB Legacy support means your motherboard has a chipset and ROM BIOS drivers that enable a USB keyboard to be used outside the Windows GUI environment. When a system has USB Legacy support enabled, a USB keyboard can be used with MS-DOS (for configuring the system BIOS) when using a command prompt within Windows or when installing Windows on the system for the first time.

If USB Legacy support is not enabled on the system, a USB keyboard will function only when Windows is running. Most recent systems include USB Legacy support, although it might be disabled by default in the system BIOS. Also, if the Windows installation fails and requires manipulation outside of Windows, the USB keyboard will not function unless it is supported by the chipset and the BIOS.

Almost all 1998 and newer systems with USB ports include a chipset and BIOS with USB Legacy (meaning USB Keyboard) support. Even though USB Legacy support enables you to use a USB keyboard in almost all situations, don't scrap your standard-port keyboards just yet.

Some Windows-related bugs and glitches reported by users include the following:

• Can't log on to Windows the first time after installing a USB keyboard. The solution in some cases is to click Cancel when you are asked to log on and then allow the system to detect the keyboard and install drivers. The logon should work normally thereafter.

In other cases, you might have to leave the keyboard unplugged when first booting and then plug it in after the OS desktop is up and running. This allows the keyboard to be detected and drivers loaded.

• Some USB keyboards won't work when the Windows Emergency Boot Disk (EBD) is used to start the system. The solution is to turn off the system, connect a standard keyboard, and restart the system.

• Some users of Windows 98 and Windows 98 SE have reported conflicts between Windows and the BIOS when USB Legacy support is enabled on some systems. This conflict can result in an incapability to detect the USB keyboard if you use the Windows 9x shutdown menu and choose to Restart the computer in MS-DOS mode. Check with the system or BIOS vendor for an updated BIOS or a patch to solve this conflict.

If you have problems with Legacy USB support, look at these possible solutions:

• Microsoft's Knowledge Base might address your specific combination of hardware.

• Your keyboard vendor might offer new drivers.

• Your system or motherboard vendor might have a BIOS upgrade you can install.

• Connect the keyboard to the PS/2 port with its adapter (or use a PS/2 keyboard) until you resolve the problem.