Analog (アナログ) is a method that represents information by varying a quantity such as voltage continuously.
It turns quantities that naturally change smoothly, such as loudness or brightness, directly into signal strength. Noise picked up along the way arrives as part of the signal and is hard to separate from the original, so quality tends to drop as the transmission distance grows.
AnalogyOn a clock with hands, the hand keeps moving without a break even between the marks on the dial.
How to rememberIt comes from the Greek analogos, meaning "proportional", which matches a signal whose strength changes in proportion to the original quantity.
Exam points
Mix-upAnalog (アナログ) and digital (デジタル) differ in whether values are shown as an unbroken continuum or as discrete values on fixed steps.
Digital (デジタル) is a method that represents information as combinations of discrete values such as 0 and 1.
A continuous waveform
Read the value at fixed intervals
Round to fixed steps
Turn it into a string of 0s and 1s
Each reading is set to the nearest step value and then replaced by a pattern of 0s and 1s.
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Inside a computer, all data is handled in this form. Even if noise distorts the waveform a little, the receiver can recover the original values by deciding again whether each one is 0 or 1, so quality holds up well through transmission and copying.
AnalogyA clock with a numeric display changes once a minute and never shows the values in between.
How to rememberIn English, digit means both "finger" and "numeral", which brings to mind discrete values counted one, two on your fingers.
Exam points
Mix-upDigitization (デジタル化) reads values at fixed intervals and rounds them to steps, so changes finer than that interval are lost. Going digital does not mean the original continuous quantity can be reproduced perfectly.
Analog vs. Digital
Aspect
Analog
Digital
Key differenceHow values are shown
Unbroken continuous values
Discrete values on fixed steps
Effect of noise
Hard to tell from the signal, so quality drops easily
Analog RGB (アナログRGB) is a video interface for connecting displays that sends the red, green and blue signals in analog form as they are.
RGB stands for red, green and blue, the three primary colors of light, and the mix of their strengths forms the colors on screen. The typical connector is the trapezoid-shaped 15-pin D-sub, also called a VGA connector. Because the signal is analog, the picture tends to blur when the cable is long or the resolution is high.
AnalogyIt is like mixing a color by smoothly turning the dimmer knobs on a red, a green and a blue lamp.
How to rememberLook at a screen through a magnifying glass and you see tiny red, green and blue dots of light, one for each letter of RGB.
Exam points
Mix-upAnalog RGB (アナログRGB) and DVI have both been used to connect PCs to displays, but analog RGB sends video in analog (アナログ) form, while DVI is based on digital (デジタル).
DVI is a video interface that connects a PC to a display and sends video in digital form.
The name stands for Digital Visual Interface, and it spread along with LCD monitors. Its connectors come in types such as DVI-D, which passes digital signals only, and DVI-I, which can pass analog signals too. The standard is for sending video and does not include audio.
AnalogyIt is like a truck with a cargo bed only for video, so sound has to go on a separate run.
Exam points
Mix-upDVI comes in types such as the digital-only DVI-D and DVI-I, which can also pass analog (アナログ) signals. Treating all DVI as digital (デジタル) only overlooks the types that also carry analog.
HDMI is an interface that carries video and audio together in digital form over a single cable.
Short for High-Definition Multimedia Interface, it is widely used on home AV equipment such as TVs, recorders and game consoles, and PCs have it too. No separate audio cable is needed, and it can also exchange signals that let the connected devices work together.
AnalogyIt is like packing video and audio into the same delivery box and shipping them together.
How to rememberThe M stands for Multimedia: the name itself says it carries "many media", video plus audio.
Exam points
Mix-upBoth DVI and HDMI can send digital (デジタル) video, but of the two, only HDMI also carries audio over the same cable.
DisplayPort is a video interface used mainly to connect PCs to monitors, and it sends video and audio in digital form.
Video interfaces
Analog
Analog RGB (no audio)
Digital
DVI (no audio; some types also carry analog)
HDMI (audio; for AV equipment)
DisplayPort (audio; for PCs)
It is a standard set by the industry group VESA and suits high-resolution output and connecting several monitors. Its connector is shaped differently from HDMI, but some products use an adapter to connect it to HDMI devices.
How to rememberAs the name says, it is the "display port": picture it as one of the sockets lined up on the back of a PC monitor.
Exam points
Mix-upDespite Display in its name, DisplayPort is not video-only: it can also send audio in digital (デジタル) form. What sets it apart from HDMI is its main use, PCs rather than AV equipment.
HDMI vs. DisplayPort
Aspect
HDMI
DisplayPort
Key differenceMain use
Home AV equipment
PCs and monitors
Audio
Carried
Carried
Defined by
A group formed by consumer electronics makers and others
VESA
Key points
Digital signals resist noise and keep their quality through transmission and copying, which is why video connections have also gone mostly digital.
Analog RGB mainly uses the 15-pin D-sub VGA connector and sends the three color signals in analog form as they are.
DVI is a video-only standard, and some of its connector types can also pass analog signals.
HDMI removes the need for a separate audio cable, so it is widely used on home AV equipment such as TVs and game consoles.
DisplayPort is a PC-oriented standard set by VESA that sends video and audio in digital form.