What Is An I/O Address?

GENERAL

I/O stands for "Input / Output." An I/O address is a piece of memory assigned to a hardware device. Many hardware devices have more than one I/O address. Your computer’s programs and operating system communicate with your hardware devices by referring to a device’s I/O addresses. I/O addresses are written in hexadecimal form

CONFLICTS

Since your computer’s programs use I/O addresses to communicate with specific hardware devices, no two devices can have the same I/O address or both would receive the same instructions from an application meant for only one device and data loss and system crashes would be the result.

Fortunately Windows doesn’t let things go this far. If two devices use the same I/O address, Windows typically disables both. Resolving the conflict may require booting into safe mode.

VIEWING THE ASSIGNMENTS

Under Windows 95 / 98:

Choose Start, Settings, Control Panel
Double click the System icon
Choose the Hardware tab
Click your right mouse button on My Computer (at the top of the list)
Choose Properties
Under Windows NT:

Choose START, PROGRAM FILES, ADMINISTRATIVE TOOLS
Choose Windows NT Diagnostics
Click the Resources tab
MOST COMMON I/O ASSIGNMENTS

Although there are some common I/O assignments typically used by certain devices, there are no real hard and fast rules. Many devices are flexible and can accept a number of I/O address ranges. If you are having problems, your best bet is to check your hardware documentation for the manufacturer’s recommendations. Remember, though, that Windows usually has no problem configuring these addresses for you and if you play around with them you might disable your computer and have to boot into safe mode to recover.

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