An input device for a computer allows the user to enter information. The most fundamental pieces of information are keystrokes on a keyboard and clicks with a mouse. These two input devices are essential for you to interact with your computer. Many other input devices exist for entering other types of information, such as images, audio and video. Input devices represent one type of computer peripheral – the other two types are output devices and storage devices.
A keyboard is the most fundamental input device for any computer system. In the early days of computing, it was typically the only input device. A keyboard contains keys for letters and numbers as well as for specialized tasks, such as Enter, Delete, etc.
When operating systems started to use graphical user interface (GUI), the mouse was developed as a pointing device. Typically, a mouse resides on a flat surface, and by moving the mouse, the user can move the pointer on the screen. One or more buttons on the mouse allow users to enter instructions by clicking. Most models also include a wheel for scrolling. In laptops, the mouse is actually substituted with a touchpad or trackpad. This is a specialized surface that follows the motion of your finger. The user can still connect an external mouse to a laptop if you prefer.
Audio and video can be recorded using a microphone and video camera, respectively. Due to the popularity of video conferencing using services like Skype, these are now typically integrated in most laptops and monitor displays for desktops; however, users can also connect an external webcam, which can record both audio and video.
Scanners as input devices
A scanner can be used to input printed images such as photographs or pages of text directly into the computer. A scanner works by shining a light at the image being scanned and measuring how much light is reflected back using an optical sensor. The amount of light that is reflected back tells the computer how light or dark the image is at each point.
The light and optical sensor reads information about one line of the image at a time. They must be moved down the picture to input the whole image. There are two different types of scanner:
- Flatbed Scanner: The user needs to place the image on top of the scanner. The scanner moves the light and sensor itself and scans the whole image automatically. Most flatbed scanners are A4 size.
- Handheld Scanner: The user must manually push the light/sensor along the image. Handheld scanners are usually 5 inches wide.
Flatbed scanners are better as they can scan larger images and are more accurate than handheld scanners. On the other hand handheld scanners are cheaper and more portable. The price of flatbed scanners has fallen so much in recent years that handheld scanners are rarely sold now. A colour flatbed scanner can be purchased for less than £100.
Optical Character Recognition (OCR) software can be used to read printed text from an image that has been scanned and store it as text rather than an image. You can then edit the text using a word processor ordesktop publisher. OCR software is not yet sophisticated enough to read hand-written text accurately.
Alternatively referred to as digital storage, storage, storage media, or storage medium, a storage device is any hardware capable of holding information either temporarily or permanently. There are two types of storage devices used with computers: a primary storage device, such as RAM, and a secondary storagedevice, like a hard drive. Secondary storage can be removable, internal, or external storage.
Examples of computer storage
- Magnetic storage devices
Today, magnetic storage is one of the most common types of storage used with computers and is the technology that many computer hard drives use.
- Floppy diskette
- Hard drive
- Magnetic strip
- Tape cassette
- Zip diskette
- Optical storage devices
- Another common storage is optical storage, which uses lasers and lights as its method of reading and writing data.
- Blu-ray disc
- CD-ROM disc
- CD-R and CD-RW disc
- DVD-R, DVD+R, DVD-RW, and DVD+RW disc
- Flash memory devices
- USB flash drive, jump drive, or thumb drive
- Memory card
- Memory stick
- Online and cloud
- Cloud storage
- Network media
Short for Digital Versatile Disc or Digital Video Disc, a DVD or DVD-ROM is a disc capable of storing large amounts of data on one disc the size of a standard Compact Disc. CD/DVD drives were first sold in 1997. They are widely used for storing and viewing movies and other data. To play DVDs on a computer, you must have a DVD drive and a software DVD player.
There are several capacities a single DVD disc is capable of holding. One of the most common DVD’s is the single-sided, single-layer disc, capable of holding 4.7 GB.
- The single-sided, double-layer disc is capable of holding between 8.5-8.7 GB.
- The double-sided, single-layer disc is capable of holding 9.4 GB.
- Although rare, the double-sided, double-layer disc is capable of holding up to 17.08 GB.
What is the difference between a DVD and a CD?
Physically, a DVD and CD look the same. Both discs are the same size and typically have one side with a label and the other side that the laser reads, unless it is a double-sided DVD. However, the technology that makes up a DVD allows for the same size disc to hold a lot more data than a CD.
A DVD is capable of holding any data and are most often used to store movie data, games, and install data for programs.
All DVD drives are capable of reading both CDs and DVDs. If you have a DVD burner, it will be capable of reading CDs and DVDs, as well as writing CD-Rs, CD-RWs, and writable DVDs.
In 1993, there were two video disc formats being developed: the Multimedia Compact Disc (MMCD) and the Super Density (SD) disc. To avoid a video format war, Philips and Sony, the backers of the MMCD, decided to partner with SD disc proponents (Hitachi, JVC, Mitsubishi, Pioneer, and Toshiba. Together, the unified industry group developed and agreed upon the DVD digital video format.
DVD’s are still very popular and widely used. However, due to more recent technologies like Blu-ray discs and streaming services like Netflix and other cloud services, DVD sales and usage have been on a steep decline.
Recent Technological Advances in Data Storage and Recording
Blu-ray or Blu-ray Disc (BD) is a digital optical disc data storage format. It was designed to supersede the DVD format, in that it is capable of storing hours of video in high-definition (720p and 1080p) and ultra high-definition resolution (2160p). The main application of Blu-ray is as a medium for video material such as feature films and physical distribution of video games for the PlayStation 3, PlayStation 4, and Xbox One.
The name “Blu-ray” refers to the blue laser (specifically, a violet laser) used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs.
The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Conventional (pre-BD-XL) Blu-ray Disc discs contain 25 GB per layer, with dual layer discs (50 GB) being the industry standard for feature-length video discs. Triple-layer discs (100 GB) and quadruple layers (128 GB) are available for BD-XL re-writer drives.
High-definition video may be stored on Blu-ray discs with up to 2160p resolution (3840×2160 pixels), at up to 60 frames per second. DVD-Video discs had been limited to a maximum resolution of 480p (NTSC, 720×480 pixels) or 576p (PAL, 720×576 pixels). Besides the hardware specifications, Blu-ray is associated with a set of multimedia formats.
HD-DVD (high-density DVD) is a high capacity optical storage medium. A single-layer HD-DVD provides up to 15 gigabytes (GB) of storage capacity and the double-layer disc offers up to 30 GB. A standard single-sided, single-layer DVD offers 4.7 GB storage capacity. A double-layer HD-DVD can contain up to eight hours of 1125-line high-density television (HDTV) programming or up to 48 hours of standard-definition television programming. The data transfer rate of an HD-DVD drive is approximately 36 megabits per second (Mbps) — more than sufficient to accommodate digital TV signals which are transmitted at 24 Mbps.
HD-DVD stores more data by:
- Using lasers with shorter wavelength: 405 nanometers (nm) in the visible blue range for HD-DVD compared with 650 nm in the visible red range for conventional DVD.
- Employing a more sophisticated data compression: An HD-DVD player can reproduce data from disks that use either the MPEG-2 standard or the more robust MPEG-4 AVC and VC-1 compression standards.
- Spacing tracks more closely together. A conventional DVD has a track pitch (spacing) of 0.75 micrometers, while HD-DVD uses a track pitch of0.40 micrometers.
HD-DVD and Blu-Ray are the two formats most often predicted to replace conventional DVDs.