Types of input devices of the computer system

In the previous session, we studied the types of devices used in computer systems. In this blog, we will explore different types of input devices in detail. A computer accepts input in two ways: manually or directly. When users enter data manually, they type or click using devices like keyboards and mice. Alternatively, users can transfer information directly from source documents, such as cheques using MICR technology, without manual input. Special direct data entry devices, like barcode readers, handle this automatic transfer. Common input devices include keyboards, pointing devices like mice and joysticks, digital cameras, and scanners. In this blog, we will learn about all these input devices in detail.

• A keyboard serves as the most common data entry device. Users type text and commands using the keyboard. Designers modeled it after a regular typewriter but added a few extra keys. Users enter data into the computer by simply pressing keys. The keyboard layout has changed very little since its introduction. In fact, the most common updates have involved adding more keys to provide extra functions. A typical keyboard contains between 84 and 104 keys.
• Portable computers, such as laptops, often feature custom keyboards with slightly different key arrangements than standard keyboards. Additionally, many system manufacturers add special buttons to the standard layout. Users find the keyboard the easiest input device because it requires no special skills. Manufacturers usually supply it with the computer, so users incur no additional cost.
• The keyboard’s maintenance and operational costs remain low. However, users may find data entry slow because they have to type all the text manually. Additionally, people with muscular disorders might find using a keyboard difficult.

• Most computers come with an alphanumeric keyboard, but some applications make the keyboard inconvenient. For example, when users want to select an item from a list, they can identify and choose the item using the keyboard. However, users can perform this action much faster by pointing directly at the correct position. A pointing device helps users communicate with the computer by allowing them to point to locations on the monitor screen.
• Such devices eliminate the need to key in characters. Instead, users move a cursor on the screen and perform actions like move, click, or drag. Commonly used pointing devices include the mouse, trackball, joystick, light pen, and touch screen.

Mouse

• A mouse is a small handheld pointing device with a rubber ball embedded on its underside and buttons on top. Typically, a mouse has two or three buttons that users press to input commands or information. We classify mice as mechanical or optical based on their technology. A mechanical mouse moves the cursor by rotating the rubber ball on its bottom as the user moves the mouse across a flat surface.
• The mouse remains the most common and least expensive pointing device. An optical mouse detects movement using a light beam instead of a rotating ball. As users roll the mouse across a specially patterned surface, the cursor moves in the same direction on the screen. Although manufacturers price optical mice higher than mechanical ones, they offer better accuracy and often eliminate the need for a mouse pad.

• With the rise of wireless technology, manufacturers have developed wireless versions of keyboards and mice. Instead of using wires, these devices connect to computers via Bluetooth, infrared, or radio frequency technologies. The wireless keyboard operates on three AA batteries, while the wireless mouse uses two AA lithium batteries.
• Manufacturers also equip wireless devices with power switches on the bottom to turn them ON or OFF. Users benefit from wireless devices by eliminating wiring tangles around the PC and gaining mobility and flexibility to position themselves relative to the computer.

Pointing Devices

• Most computers include an alphanumeric keyboard, but some applications make the keyboard inconvenient. For example, when a user wants to select an item from a list, they can identify and select items using the keyboard. However, users can perform this action more quickly by pointing directly at the correct position. Pointing devices allow users to communicate with the computer by indicating locations on the monitor screen.
• These devices do not require users to key in characters; instead, users move a cursor on the screen to perform move, click, or drag operations. Commonly used pointing devices include the mouse, trackball, joystick, light pen, and touch screen.

Trackball

• A trackball serves as another pointing device and resembles a ball nestled in a square cradle, acting as an alternative to a mouse. Essentially, a trackball looks like an upside-down mouse. When users rotate the ball with their fingers in any direction, the cursor moves accordingly. Trackball balls vary in size from as large as a cue ball to as small as a marble.
• Since users keep this device stationary, they move the ball on top using their fingers, thumbs, or palms instead of rolling a mouse on the table. This pointing device appears in various shapes and forms but performs the same functions. People commonly use three shapes: ball, button, and square.

• A joystick moves in all directions and controls the cursor’s movement. Its basic design includes a stick attached to a plastic base covered by a flexible rubber sheath. The plastic base contains a circuit board beneath the stick. The electronic circuitry measures the stick’s movement from its central position and sends that information for processing.

• A joystick also includes buttons that users can program to trigger certain actions after selecting a position on the screen with the stick. It offers three types of control: digital, glide, and direct. Digital control restricts movement to limited directions such as up, down, left, and right. Glide and direct control allow movement in all directions (360 degrees). Direct control joysticks also respond to how far and how fast the user moves the stick.
• Users generally use a joystick to control the speed of the cursor’s movement on the screen rather than its exact position. People mostly use it for computer games. Other common applications include flight simulators, training simulators, CAD/CAM systems, and controlling industrial robots.

Light Pen

• Sometimes, people have information like pictures or text only on paper but need to transfer it to a computer for further use. A scanner converts these physical documents into electronic formats that users can save on a disk. Users can then edit, manipulate, combine, or print the digital images using image editing software. People also call scanners optical scanners because they use a light beam to scan the input data.
• Most scanners include a utility program that helps them communicate with the computer and save the scanned image as a graphic file. Additionally, scanners store images in both grayscale and color modes. People commonly use two types of scanners: hand-held scanners and flat-bed scanners.

• A hand-held scanner uses light-emitting diodes (LEDs) positioned over the document. It scans the document slowly from top to bottom while the light stays on. During this process, the scanner converts the document into an image and stores it. To get the best results, the user must drag the scanner steadily and carefully over the document at a constant speed without stopping or jerking.
• People commonly use hand-held scanners in situations where extremely high accuracy is not critical. Manufacturers make them small in size and offer various resolutions, typically up to about 800 dpi (dots per inch). Users can choose from both grayscale and color models.
• Furthermore, people prefer hand-held scanners when they need to scan a small volume of documents. They often use these scanners to read data from price tags, shipping labels, inventory part numbers, book ISBNs, and similar items.

2.Flat-bed Scanner

• Flat-bed scanners resemble photocopier machines. They have a box with a glass plate on top, covered by a lid. To scan a document, the user places it on the glass plate. When activated, a light beam moves horizontally from left to right beneath the glass and scans the document.
• After scanning one line, the light beam moves down to scan the next line and repeats this process until it covers the entire document. Scanning an A4-sized document usually takes about 20 seconds. These scanners can capture black-and-white and color images.
• Flatbed scanners cost more and take up more space than hand-held scanners. However, they typically produce higher-quality images because they use advanced scanning technology.

Optical Character Recognition (OCR)

• As stated earlier, a scanner converts an input document into an electronic format and stores it on the disk. If the document contains an image, you can manipulate it using image editing software. If the document contains text, you need optical character recognition (OCR) software. When the scanner scans a document, it stores the scanned document as a bitmap in the computer’s memory. The OCR software then translates the bitmap image of the text into ASCII codes so the computer can interpret the data as letters, numbers, and special characters.
• OCR makes data entry easier, faster, and less error-prone. However, it costs a lot, and if the document has poor typing or unclear text, OCR will struggle to recognize the characters. In addition, text scanning loses most document formatting except for tab stops and paragraph marks. A finished text scan produces a single-column editable text file. You will need to spell-check, proofread, and reformat this text file to achieve the desired final layout.

Optical Mark Recognition (OMR)

• Optical mark recognition detects the presence of marked responses on a paper. A mark registers significantly less light than the surrounding paper, allowing the system to detect it. A special device called an optical mark reader performs this task. To ensure detection, you need to place the mark in the correct position on the paper and make it significantly darker than the surrounding area.
• The OMR technology enables a high speed reading of large quantities of data and transferring this data to computer without using a keyboard. Generally, this technology is used to read answer sheets (objective type tests). In this method, special printed forms/documents are printed with boxes, which can be marked with dark pencil or ink. These forms are then passed under a light source and the presence of dark ink is transformed into electric pulses, which are transmitted to the computer.
• OMR has a better recognition rate than OCR because fewer mistakes are made by machines to read marks than in reading handwritten characters. Large volumes of data can be collected quickly and easily without the need for specially trained staff. Usually, an OMR reader can maintain a throughput of 1500 to 10000 forms per hour.
• However, the designing of documents for optical mark recognition is complicated and the OMR reader needs to be reprogrammed for each new document design. OMR readers are relatively slow because the person putting marks on the documents must follow the instructions precisely. Any folding or dirt on a form may prevent the form from being read correctly. In addition, it requires accurate alignment of printing on forms and needs a paper of good quality.

Magnetic Ink Character Reader (MICR)

• You must have seen special magnetic encoding using characters, printed on the bottom of a cheque. The characters are printed using special ink, which contains iron particles that can be magnetized. To recognize these magnetic ink characters, a magnetic ink character reader (MICR) is used. It reads the characters by examining their shapes in a matrix form and the information is then passed on to the computer.

• Bar code is a machine-readable code in the form of a pattern of parallel vertical lines of varying widths.It is commonly used for labelling goods that are available in super markets and numbering books in libraries. This code is sensed and read by a bar code reader using reflective light.
• The information recorded in bar code reader is then fed into the computer, which recognises the information from the thickness and spacing of bars. Bar code readers are either hand-held or fixed-mount. Hand-held scanners are used to read bar codes on stationary items.
• With fixed-mount scanners,items having a bar code are passed by the scanner by hand as in retail scanning applications or by conveyor belt in many industrial applications.
• Bar code data correction systems provide enormous benefits for just about every business with a bar code data-collection solution, capturing data is faster and more accurate. A bar code scanner can record data five to seven times faster than a skilled typist. A bar code data entry has an error rate of about 1 in 3 million. Bar coding also reduces cost in terms of labour and revenue losses resulting from data collection errors. Bar code readers are widely used in supermarkets,department stores, libraries, and other places.
• You must have seen bar codes on the back cover of certain books and greeting cards. Retail
  and grocery stores use a bar code reader to determine the item being sold and to retrieve the
  item price from a computer system.
• Bar code scanners are electro-optical systems that include a means of illuminating the symbol and measuring reflected light. The light waveform data is converted from analog to digital, in order to be processed by a decoder, and then transmitted to the computer software. The process begins when a device directs a light beam over a bar code.
• The device contains a small sensory reading element, called sensor,which detects the light being reflected back from the bar code, and converts light energy into electrical energy.
• The result is an electrical signal that can be converted into an alphanumeric data.The pen in the bar code unit reads the information stored in the bar code and converts it into a series of ASCII characters by which the operating system gets the information stored in the bar code.

Conclusion