Wednesday, July 20, 2011

Instruction Set Architecture (ISA)

It marks the division betweein hardwar eand software. The concept of ISA was first clearly articulated when IBM 360 familiy in early 1960. The importance of software compatibility was fully recognized. IBM 360 has a number of model incorporated with a wide range of hardware resources but all of them could run the same software. There are 2 parts of ISA. User ISA is visible to application program, System ISA is visible to supervisor such as operating systems.

The application binary interface (ABI) provides a program with acc ess to hardware resources and services available in the system. ABI contains all user instruction. It also contains system call interface which allows application to invoke operating system to perform works on behalf of itself.

The application programming interface (API) is usually defined with respect to a high level language. The API can include system call provided by the operating system (wrapper). API enable applications written to be ported easily (via recompilation) to any sytem that supports the sampe API.

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