Identify three widely used display interfaces for connecting a video card to a computer monitor, and specify the type of signal (analog or digital) and a primary characteristic of each.

### Why this is right The key difference is how each interface encodes the picture signal. Video Graphics Array (VGA) sends an analog signal, while Digital Visual Interface (DVI) can send analog, digital, or both, depending on its version. High-Definition Multimedia Interface (HDMI) and DisplayPort send digital video and can carry audio over the same cable. ### The concept An **analog signal** represents picture information as a continuously varying electrical voltage; a **digital signal** encodes it as discrete values. VGA is an older video connection, used especially with cathode-ray tube (CRT) displays and some early liquid-crystal display (LCD) monitors; it carries video, not audio. DVI bridged older and newer equipment: DVI-D is digital, DVI-A is analog, and DVI-I can carry either. HDMI and DisplayPort are digital interfaces commonly used with modern monitors; their ability to support high resolutions, such as 4K, and high refresh rates depends on the particular equipment and version. A **refresh rate** is how often a display updates its image each second. | Interface | Signal | Main characteristic | |---|---|---| | VGA | Analog | Older video-only connection | | DVI | Analog, digital, or both | Different versions support different signal types | | HDMI or DisplayPort | Digital | Can carry video and audio on one cable | ### What a good answer covers - Name three interfaces: VGA, DVI, and either HDMI or DisplayPort. - Identify VGA as analog. - Explain that DVI’s signal type depends on its version. - Identify HDMI and DisplayPort as digital interfaces that can carry video and audio together. ### Watch out DVI is not always digital: its suffix matters. Also, VGA’s connector shape does not make its signal digital; VGA carries analog video. ### Terms - **VGA**: Video Graphics Array. An older interface that carries analog video. - **DVI**: Digital Visual Interface. A family of interfaces that can carry digital video, analog video, or both. - **DVI-D**: Digital Visual Interface, Digital. The digital-only version. - **DVI-A**: Digital Visual Interface, Analog. The analog-only version. - **DVI-I**: Digital Visual Interface, Integrated. The version that can carry digital or analog video. - **HDMI**: High-Definition Multimedia Interface. A digital connection for video and audio. - **CRT**: Cathode-Ray Tube. A display technology that forms images using an electron beam inside a tube. - **LCD**: Liquid-Crystal Display. A display technology that uses liquid crystals to control light and form images. - **4K**: A display resolution category with roughly four thousand pixels across the image. - **DisplayPort**: A digital display interface that can carry video and audio. - **Analog signal**: A signal whose value varies continuously to represent information. - **Digital signal**: A signal that represents information using discrete encoded values. - **Refresh rate**: The number of times per second a display updates its image. ### Remember VGA is analog, DVI depends on its version, and HDMI or DisplayPort carries digital video and audio.