Informatics Practices · Ch 1 — Computer System
Input Devices
Input Devices
A computer can process only what reaches it, and it understands only digital signals. Input devices are the devices through which control signals are sent to a computer. Their defining job is conversion: they take the data we supply and convert it into a digital form that the computer system can accept. Whatever we press, touch, speak or scan must become digital data before the machine can work on it.
Common input devices
Some familiar examples of input devices (shown in Figure 1.2) are:
- Keyboard — for typing in text, numbers and commands,
- Mouse — for pointing and selecting,
- Scanner — for capturing printed pages or images into the computer,
- Touch screen — where the display surface itself accepts input from the finger.
Input for accessibility and beyond
Input is not limited to the standard keyboard and mouse. Specially designed braille keyboards are available to help the visually impaired enter data into a computer — a reminder that input devices can be adapted so that computing remains usable by everyone.
Voice has also become a practical input channel. We can now enter data simply by speaking: with Google voice search, for instance, the search string is given to the web through our voice instead of being typed.
Where the input goes
What happens to data once an input device hands it over? Two destinations matter:
- Data entered through an input device is first stored temporarily in the main memory of the computer system, also called RAM. This is the working space where data waits while processing goes on.
- For permanent storage and future use, both data and instructions are stored in additional storage locations called secondary memory. …
The figure is a bordered panel presenting four photographs stacked one above the other, each with its name printed beneath it. The four devices pictured are a keyboard, a mouse, a flatbed scanner, and a hand holding a smartphone to illustrate the touch screen.
Each photograph is a concrete example of the section's central idea: an input device is the doorway through which control signals and data enter a computer, converted into the digital form the machine can accept. The keyboard represents typed input of text and commands; the mouse represents pointing and selecting; the flatbed scanner represents capturing an existing printed page or picture into digital form; and the smartphone held in a hand shows the touch screen, where the display itself is the input surface and a fingertip does the work of both keyboard and mouse. …