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A hard drive stores all your data. it houses hard disks, where all your files and folders are physically located. A typical hard drive is only slightly larger than your hand, yet can hold over 100 GB of data. The data is stored on a stack of disks that are mounted inside a solid encasement.
In the real world, "optical" refers to vision, or the ability to see. In the computer world, however, "optical" refers to lasers, which can "see" and read data on optical discs. These discs include CDs and DVDs, which are made up of millions of small bumps and dips. Optical drives have lasers that read these bumps and dips as ones and zeros, which the computer can understand
Whenever you enter data into your computer, it is referred to as input. This can be text typed in a word processing document, keywords entered in a search engine's search box, or data entered into a spreadsheet. Input can be something as simple as moving the mouse or clicking the mouse button or it can be as complex as scanning a document or downloading photos from a digital camera
Data generated by a computer is referred to as output. This includes data produced at a software level, such as the result of a calculation, or at a physical level, such as a printed document. A basic example of software output is a calculator program that produces the result of a mathematical operation. A more complex example is the results produced by a search engine, which compares keywords to millions of pages in its Web page index.
A touchscreen is a display that also serves as an input device. Some touchscreens require a proprietary pen for input, though most modern touchscreens detect human touch. Since touchscreen devices accept input directly through the screen, they do not require external input devices, such as mice and keyboards. This makes touchscreens ideal for computer kiosks, as well as portable devices, such as tablets and smartphones.