a circuit board that can be added to a computer to enable it to record and reproduce sound or provide superior sound quality than the audio circuit of the motherboard. Sound cards often include other features such as a MIDI musical instrument interface, a controller for a CD-ROM drive, and an audio amplifier that can drive speakers. See Figure 247.

1. (coder-decoder or compressor-decompressor) an electronic circuit for converting audio or video signals into and out of digital form; th essential part of a sound card or a card for processing images from a video camera.
2. a software component that performs a similar function, for handling audio and video files in a specific format.

a computer that represents information in a form that can vary smoothly between certain limits rather than having discrete values. (Contrast digital computer.) A slide rule is an example of an analog computer because it represents numbers as distances along a scale.

All modern, programmable computers are digital.Analog computer circuits are used in certain kinds of automatic machinery, such as automotive cruise controls and guided missiles. Also, a fundamental analog computer circuit called an operational amplifier is used extensively in audio, radio, and TV equipment.