Practical No. 1

PRACTICAL NO.-1 Aim: Practical for Study of Keyboard, Keyboard Layouts, Keyboard Connectors, Keyboard Switch Types, Keyboard Troubleshooting.

Introduction: The Basic functionality of the PC Keyboard has changed little in the almost 20 years since the release of the original IBM PC. The number of keys has increased, from 83 to 84 to 101 and now 104 and there are two different connectors ,but the interface with the computer is the same. You can plug a keyboard from virtually any PC into any other PC and it will function. The keyboard is the main input peripheral used by all computers. The keyboard allows for user input and action with the computer. Much like many type writers, the keyboard has all the letters of the alphabet, numbers 0 - 9 and additional special operational keys. Some of the keys have a special use. There are referred to as command keys. The 3 most common are the Control or CTRL, Alternate or Alt and the Shift keys though there can be more (the Windows key for example or the Command key).. A keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, which act as mechanical levers or electronic switches. A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence.

Keyboard Layouts: The layout of the PC keyboard has changed over the years, as the keys were added and their arrangement modified for greater ease of use. The four keyboard layouts used for most desktop PCs are as follows:  83-key PC/XT keyboard.  84-key AT keyboard.  Enhanced 101-key keyboard.  Windows 104-key keyboard. These keyboard types are examined in the following sections:

The 83-key PC/XT keyboard: The very first PC keyboard was the old 83-key keyboard used by IBM for the very first IBM PCs and PC/XTs in the early 1980s. This design was copied nearly verbatim by most of the early "clone" makers, and was the standard for PCs of this era. In looking at this keyboard one must bear in mind that we are going back almost 20 years, an eternity in the computer industry (which is arguably only about 50 years old period). There are many valid criticisms of the first keyboards, but in fact, IBM made several good decisions for which one must give them credit. For starters, they made a good decision in making the keyboard detachable from the PC at all; we take that for granted, but many small computers of that era, such as the Apple ][, had the keyboard integrated into the system box. A detachable keyboard was a distinct improvement. Of course, with the first keyboards IBM also engineered the keyboard interface, cabling and signaling standards that are mostly still in use today. In terms of construction these keyboards were very much appreciated by many typists because

they were rock solid, with high-quality key switches and heavy, metal cases. (Pick up an original IBM keyboard and you'll understand why people say they were "built like a tank".) They are also fairly small and compact dimensionally, taking up relatively little desk space. Here are some of the main issues with this layout, when it is contrasted to more modern configurations:  Cramped Physical Grouping.  Poor <Shift> Key Size and Location.  Poor <Enter> Key Size and Location.  Strange Key Size and Position.  No Dedicated Cursor and Navigation Keys.  No Indicator LEDs.

NOTE: Some PC/XT keyboards include LEDs, but these work solely by tracking keystrokes and do not indicate the condition of the toggles on the motherboard. This means that it is possible for the LEDs to get out of sync with the motherboard signals and display the wrong information.

The 83-key PC/XT keyboard layout

The 84-key AT keyboard: Looking at the number of issues regarding the original 83-key XT keyboard, you can see that it's a pretty long list. Of course, in the early 1980s IBM received a lot of complaints about the first keyboard design and eventually made improvements to it. The first evolution of the keyboard was the 84key keyboard layout introduced with the first IBM PC/AT. Unsurprisingly, this is sometimes called the AT Keyboard. There are several definite improvements with this layout, compared to the 83key keyboard:  Better Physical Grouping.  Improved <Shift> and <Enter> Keys.  LED Indicators.  Extra "System Request" Key. However, many of the layout issues with the original design remained. The biggest concern that remained unaddressed was the continued sharing between the numeric keypad, and the cursor and navigation keys. The function keys are still on the lefthand side, and the and keys are still different from what a typist would expect. Some PC users also believe that this keyboard layout took one step backwards, in relocating the <Esc> key. This key is used rather frequently, and moving it from a position where it could be easily hit with the left pinky or ring finger, to the numeric keypad, was an annoyance.

This keyboard was changed internally from the PC/XT model as well. The interface was made bidirectional, allowing the system to send commands to the keyboard, and enabling the control of the new LED indicators. The signaling and interface protocols created with this first PC/AT keyboard are still used today, even though the 84-key layout is no longer used, having been replaced by the "Enhanced" 101-key keyboard.

The 84-key AT keyboard layout

The Enhanced 101-key keyboard: In 1986, IBM introduced the IBM PC/AT Model 339. Included in this last AT-family system was the new Enhanced 101-key keyboard. Little did IBM realize at the time, perhaps, but this 101-key keyboard would become the de-facto standard for keyboards for the next decade and beyond. Even today's Windows keyboards and fancy variants with extra buttons and keys are based on this layout.

Closeup photo of a 101-key "Enhanced" keyboard

The "Enhanced" keyboard was electrically the same as the 84-key AT keyboard, but featured a radically redesigned key layout. The major changes included these:      

Dedicated Cursor and Navigation Keys. Relocated Function Keys. Relocated <Esc> and Keys. Extra Function Keys. Extra and Keys. Extra Numeric Keypad Keys.

Compared the 84-key keyboard the Enhanced keyboard layout was perceived by most users to be far superior. It was an immediate hit despite its one obvious inferiority to the AT keyboard: the smaller main <Enter> key. (The <Space Bar> is also a bit smaller.) Obviously, some of the changes made with the Enhanced keyboard are undeniable. However, others are in this author's opinion good examples of the old warning: "be careful what you ask for"...

The beefs with this layout involve the locations of the following:  Left Key : The new design puts the key below the main keyboard, requiring a move of the entire left hand to reach it. And while having the key above the left <Shift> may be of use to some.  Function Keys: Having the function keys on the left-side of the keyboard makes them easy to reach, particularly in combination with the <Shift>, and keys. Again, these are frequently used keys which are hard to reach when above the keyboard; most combinations that used to be simple with one hand now require two. For example, a command I use frequently when writing is +, the Microsoft Word (and FrontPage) function to switch between documents.  <Esc> Key: This key is still a reach with the Enhanced design.

The Windows 104-key keyboard: Despite being a software company, Microsoft has always manufactured and sold input device hardware.As Windows became the predominant operating system in the PC market, Microsoft realized that many common Windows functions had no simple keyboard short-cuts to activating them. Seizing their leadership position, they created a specification for a new variant of the 101-key keyboard that includes special keys to activate common Windows functions.

Closeup photo of a black 104-key Windows keyboard

These so-called "Windows keyboards" are in fact almost identical to the regular 101key Enhanced design. They simply add three additional "Windows" keys, making room for them by stealing real estate from the , and <Space Bar> keys along the bottom of the keyboard. Since the Windows keyboard offers some flexibility that the regular Enhanced layout does not, and its cost of production is virtually unchanged, it quickly replaced the Enhanced layout as the de-facto standard on most PCs. Most keyboards today, whether they are included with new PCs or sold separately, are some variation of the 104-key Windows keyboard layout.

Laptop Keyboard: A laptop keyboard is an input device used with a laptop computer. Like a keyboard for a desktop computer or a typewriter, the keys are used to type individual symbols. A standard laptop keyboard takes on a flat layout attached to the bottom of the monitor, and can feature different arrangements of keys and symbols. Most laptop keyboards condense multiple symbols into fewer buttons to accommodate for less space.

These keyboards have letters A through Z and numbers 0 through 9 in the common QWERTY layout -- named for the first six letters in the top row of the alphabetic layout. These keyboards also come with the space bar, shift keys, and enter and delete keys common to typing keyboards. Escape keys and 10 to 12 specialized F keys are also commonplace. Laptop keyboards differ from most desktop keyboards in that they will condense buttons to save space and make for a smaller product. Usually a second set of numbers, often found on the right side of the keyboard, are left off of a laptop keyboard. Other keys are often combined into sets with a letter or number symbol, and utilized through the shift command. Unlike desktop keyboards, laptop keyboards do not feature a traditional computer mouse. Many laptop keyboards feature a scrolling pad for control of the arrow on the screen. This pad, fingertip sensitive, will move the arrow along with slight finger movements on the pad. Along with the pad are the right- and left-click buttons commonly found on the mouse. A page-scrolling device, often found between the right- and left-click buttons on the mouse, can usually be found to either side of the fingertip pad.

Keyboard Connectors: PC keyboards connect to the motherboard on the computer using one of three different connectors. Two of these, the 5-pin DIN connector and the 6-pin mini-DIN , have been in use for many years. The third, the USB connector, is a relatively new innovation.

The 5-pin DIN connector: The s-pin DIN connector is the oldest of the keyboard connectors. Rarely, if even, seen on new computers today, this connector is found on the older keyboards and computers with motherboards that use the Baby-AT form factor. The connector itself, shown in the figure, is ½ inch in diameter, with 5pins arranged in a semicircular pattern. The keyboard has the male connector at the end of its cable, and the computer has a female connector attached directly to the motherboard, in most cases, the plug on the keyboard has an arrow on it that you can use to line up the pins with the socket. The arrow should point to the top surface of the motherboard.

5-pin male connector

6-pin female connecto

Pin Number

Signal

1 2 3 4 5

Keyboard Clock Keyboard Data Unused Ground +5v Power

The 6-pin Mini –DIN connector: It is also called a PS/2 connector, after IBM system that first used it.it is 5/16 inch in diameter, a little more than half the size of the 5-pin DIN. It is designed to use six pins arranged in a circular pattern around a rectangular plastic key that ensures the proper alignment of the plug and the socket. The pinouts for the connector are shown in table. The computers have two identical mini-DIN ports, usually side by side. However, the data packets used by the two devices are different, and you must plug the keyboard and the mouse into the correct sockets for them to function properly.

6-pin male and female connector

6-pin male connector

Pin Number

Signal

1 2 3 4 5 6

Keyboard Data Unused Ground +5V Power Keyboard Clock Unused

The USB connector: The universal serial bus is a multifunction peripheral bus that is growing rapidly in popularity, and the keyboard is one of many devices that can use it. Most of the PCs produced today include USB ports, but they still retain their standard keyboard connectors as well. There are two types of USB ports and connectors, Type A and Type B.

1) Type A: Type A ports and connectors are small and rectangular and are typically used to plug a device into a Type A USB port on a computer or a hub. Type A ports and connectors are sometimes referred to as "upstream".

USB Type A port and connector

USB Type B port and connector

2) Type B: Type B ports and connectors are small and square and are used to attach a USB cable to a USB device. Type B ports and connectors are sometimes referred to as "downstream".

Keyboard Working Criteria:

Keyboard Troubleshooting: There are many troubleshooting with keyboard as follows:  There is an apparent failure of the keyboard.  Sometimes suspect a failure or problem with the keyboard controller.  The system does not respond when we try to reboot it by pressing {Ctrl}+{Alt}+{Delete}  One or more of the keys on our keyboard is sticking, bouncing, repeating, or not generating a keystroke reliably.  There is a loud ringing or repeated beeping sound from the PC speaker when keyboard is connected to the system.

 Sometimes we have a keyboard that we want to connect to our PC but the connector is the wrong size.