DVI vs D-Sub
D-sub is a standard for electrical connectors that were commonly used with computer and its accessories. The sub is a shortened version of subminiature, which seems pretty laughable considering the huge physical size of this connectors compared to the common connectors nowadays. But during its time, the D-sub was a relatively small connector. DVI is a fairly new specification that also defines a new connector for use with displays. It aims to replace the aging D-sub connector for displays currently in prominence.
DVI was purposely developed and designed to transmit video signals. In comparison, the D-sub connector is used for a much wider variety of applications. This includes but not limited to VGA displays, serial ports, parallel or printer ports, game pads, and even for mice. D-sub connectors were steadily being replaced by other types of connectors, the most prominent of which was USB. The only D-sub connector that is still being widely used nowadays is the DE9 connector for monitors.
DVI is capable of transmitting both analog and digital signals its D-sub equivalent (the DE9) only carries analog signals. Though other D-sub connectors like the serial port uses digital signals, the provisions in the VGA standard only allows analog signals.
In terms of the actual connector, the two looks very similar as they both sport the shell that looks like a lying down D, with the curve on side to ensure the proper orientation of the connector. DVI is specific to video displays and there is really no point in having a wide selection of connectors that can be confusing. There are three standard connectors for DVI with the standard DVI connector for desktop computers and the smaller version for smaller devices like laptops. In contrast, there are five standard shell sizes for D-sub not to mention the great number of pin count and configurations. This is a direct consequence of the wide number of uses of the D-sub connector. Even coaxial cables have been included in them at one point.
Summary:
1. D-sub was a standard for computer connectors while DVI is a standard connector for video displays
2. DVI is fairly new while D-sub is a very old and almost obsolete standard
3. DVI is used purely for displays while D-sub was used for a wide variety of applications
4. DVI is capable of transmitting analog and digital signals while its D-sub equivalent is only capable of analog signals
5. DVI comes in three standard sizes while D-sub has a wide variety of shell sizes and pin counts