2.1 Getting the input data

There are various ways a computer gets its imput data. This part depends greatly on the application of the computer.

2.1.1 Conventional information system

A conventional information system acquires its input data already encoded in a form that is easy to process. The acquisition mechanisms include the following:

• User input. Some data are entered by data entry clerks or other personnel. The devices used for data input include the keyboard, the mouse, and numeric keypads. In the past, computers have specialized “ports” for these devices. However, recent computers use USB (universal serial bus) to connect to all these devices.
• Networking. Most information systems are now network connected, and acquire most input data via the network interface. A NIC (network interface card) converts electrical, optical or radio wave signal into digital data. Network connectivity permits a system to acquire data via interactive web scripts, or directly import data from another computer.
• Data storage media. Although computer networks have advanced over time, sometimes it is still more cost effective to store data on media (such as tapes and optical disks) and transport the media from one location to another. Most data storage media require a drive to convert the stored data to a form that a computer can process.

2.1.2 Personal computer

A personal computer share many of the input mechanisms as an information system. However, a personal computer also has additional methods to acquire data for more “personal” uses.

• Scanners. A scanner captures images from paper, transparencies or film media. Image data is captured as pixel (picture element) data. Each pixel is a point of an image. In the past, scanners interfaced with computers via parallel ports, specialized ports or SCSI (small computer system interface). Modern scanners, on the other hand are mostly USB based, except for the high-end commercial type.
• Webcam. A “webcam” is essentially an inexpensive video camera that transmits video images to a computer. The term “webcam” is coined because most people use such cameras for meetings over the web. Interesting, webcams are also used for authentication on some personal computers. The computer monitors a webcam for faces that it has registered, and logs into the account corresponding to the face that is recognized.
• Microphone. A microphone allows a computer to capture audio data. Most webcams are equipped with microphones. However, there are studio-quality micromouses that capture high quality audio that is suitable for music recording. In the past, microphones must be connected to a sound card, and a sound card converts the electrical signal (which in return is converted from audio signal) into data. However, as with most other human interface devices (HID), modern microphones now connect to computers via USB directly.

2.1.3 Embedded computers

Embedded computers have all sorts of input devices. From temperature sensors to scanning LIDAR (light detection and ranging), all kind of devices were invented for different applications. It is impossible to list even the most common types of input devices that feed data to embedded computers.

Nonetheless, most embedded computers acquire their input data from an ADC (analog to digital converter). An ADC converts an electrical signal (as a voltage) to a number that can be read by a computer. The electrical signal is “transduced” by sensors. For example, a thermal couple is a device that produces a different voltage depending on temperature. Then an ADC converts the varying voltage to numbers that change with temperatures. As a result, an embedded computer can interpret the number and convert it as a temperature.

Sensors exist for every application. For example an accelerometer senses force (such as gravity), and is often used in application where tilt and acceleration are to be measured. A strain gauge, on the other hand, converts strain (from bending, for example) to a voltage to be measured. Humidity sensors sense relative humidity.

And so on.