Primary input device of the computer and used to enter commands and type text. It’s similar to typewriter.
Present day keyboards have 101 or more keys
Main types of keys on a Windows keyboard are :
PC/AT keyboard was a part of the PC/AT computer introduced by IBM and it had 84 keys
101-Key Enhanced – major drawback – a small Enter key. This layout continues to be used even today
102-Key Enhanced – for non-English users
104-Key Windows – Microsoft introduced this key board. Three keys included are two identical keys to open start menu and one key to perform the right click
Ergonomic – designed keeping in mind the comfort of the user and also known as natural key board. It includes wrist rests and the angle between two halves can be adjusted. It is difficult to use if you are not experienced typist. It is expensive and consume more space
Programmable – an important key is Remap. User can swap the keys. It will be in effect even if the keyboard is connected to another computer. It can also create macros. It’s not very popular as most users consider the additional features unnecessary. If the keyboard is not used carefully it could change functions of important keys without user even realizing it
Multimedia – added functionality to open mail clients, multimedia player, internet browser and search programs, go back and forth in web browser, volume control and jump from one file to another in a multimedia player
Cordless -
5-pin DIN5 connector
6-pin PS/2 connector
4-pin USB connector
Has a microprocessor that studies the state of each key on the keyboard and sends the appropriate signal to the computer
Grid of circuits underneath keys on keyboard known as key matrix
Circuits below all keys are broken
Circuit is closed, and microprocessor detects closed circuit – when pressing a key
Microprocessor detects the closed circuit and notes the position of the circuit on the key matrix
Microprocessor has a character map of the keyboard in its ROM
Compares the location of the closed circuit to the same location in the character map
Processor analyses the key matrix and decides on the characters to be sent to the computer through a connector
When you press a combination of characters, processor compares the combination to character map and see if there is any designation for that particular combination
These characters are maintained in am memory buffer and then sent in a stream to the computer
Keyboard is a largely a trouble-free device if handled properly
Do not spill liquids or food particles on the keyboard
Problem that may occur with keyboards are :
Douglas Engelbart invented mouse
The name is so because the appearance and movement are very similar to that of a mouse
Enables user to move cursor or pointer to specific point on screen
Can have two or three buttons or a scroll button
When you move the mouse, the cursor on the screen also moves in the same direction
Mouse is important for Graphical User Interface (GUI) applications
You can use the mouse to draw objects on the screen
Mechanical Mouse – consists of rubber or metal ball and mechanical sensors (VARIAC)
Optomechanical Mouse – use optical sensors instead of mechanical sensors and more accurate
Optical Mouse – uses laser technology and most accurate and precise type of mouse.
Cordless Mouse – uses an infrared or radio link and operates on batteries
Serial Connector
PS/2 Connector
USB Connector
Mouse converts the movements to signals that the computer can use
Mouse has a ball inside its body that rolls around as mouse is moved
Two rollers are angled so that one senses the movement of the mouse ball in the X-direction and the other in the Y-direction and touch the ball
Roller connected to a shaft and shaft moves a disk that has many holes in its periphery
Infrared LED provides light, which shines on the disks
As the disk rotates, the beams of light are broken due to the gaps between the holes on the disk
Infrared sensor senses pattern of light
Mouse processor receives signals form the sensor and converts signals to binary data
Send to the computer through cord and connector
If you installed a serial mouse, check the CMOS settings to ensure that the serial or COM ports are enabled and assigned
If you installed a USB mouse, check the CMOS settings to ensure that the USB is enabled. Also ensure that USB legacy support is enabled
Mouse can give problems if not handled with care
Do not spill liquid or other substances around the mouse
Problems that may occur with mouse are :
