Editing POST card (section)

==Usage scenarios==
[[File:POST ("port 80") displays on a computer motherboard.jpg|thumb|Two POST seven-segment displays ("Q_CODE1" and "Q_CODE2", lower-left), integrated on a computer motherboard]]

Diagnostic cards are today mainly used by designers of motherboards and extension cards, along with [[logic analyzer]]s and other debug tools and interfaces. They are less commonly used in the 21st century for computer repair and by system integrators, but remain available. POST cards for PCs, while originally high-priced, cost from just a few [[US dollar]]s upwards in the 21st century.

Some motherboards have a built-in display to diagnose hardware problems. Most also report POST errors with audible beeps, if a PC speaker is attached. Such motherboards make POST cards less necessary.

When these diagnostic cards were first introduced motherboards were expensive and well worth troubleshooting and repairing. By the late twentieth century [[large scale integration]], [[mass production]] made motherboards inexpensive components. Motherboards were rarely repaired, but replaced; the main purpose of a POST card is to determine that parts mounted on the motherboard itself, rather than plugged-in video cards, RAM, etc. are at fault.