(1) (Instruction Set Architecture) See instruction set.

(2) (Interactive Services Association) See Internet Alliance.

(3) (Internet Security and Acceleration) See .NET.

(4) (The Instrumentation, Systems, and Automation Society, RTP, NC, www.isa.org) A trade association founded in 1945 that is dedicated to industrial control systems which includes measurement and instrumentation, robotics, motion control and process control. ISA supports ISA EXPO, the industry's premier trade show for more than 50 years as well as the Directory of Instrumentation.

(5) (Industry Standard Architecture) Pronounced "eye-suh." An expansion bus commonly used in earlier PCs that accepted plug-in boards for sound, video display and other peripheral connectivity. Originally called the "AT bus," which was introduced with the IBM PC AT in 1984, the AT/ISA bus extended the PC bus from 8 to 16 bits. For several years, many motherboards provided a mix of both 8-bit and 16-bit ISA slots. As PCI became popular, motherboards included only 16-bit ISA and PCI, and by the early 2000s, began to phase out ISA entirely. See PC data buses.