32-bit application

architecture, operating system IBM PC software that runs

in a 32-bit flat address space.

The term 32-bit application came about because MS-DOS and

Microsoft Windows were originally written for the Intel8088 and 80286 microprocessors. These are 16 bit

microprocessors with a segmented address space. Programs

with more than 64 kilobytes of code and/or data therefore had

to switch between segments quite frequently. As this

operation is quite time consuming in comparison to other

machine operations, the application's performance may suffer.

Furthermore, programming with segments is more involved than

programming in a flat address space, giving rise to some

complications in programming languages like "memory models"

in C and C++.

The shift from 16-bit software to 32-bit software on IBM PC

clones became possible with the introduction of the Intel80386 microprocessor. This microprocessor and its successors

support a segmented address space with 16-bit and 32 bit

segments (more precisely: segments with 16- or 32-bit address

offset) or a linear 32-bit address space. For compatibility

reasons, however, much of the software is nevertheless written

in 16-bit models.

Operating systems like Microsoft Windows or OS/2 provide

the possibility to run 16-bit (segmented) programs as well as

32-bit programs. The former possibility exists for backwardcompatibility and the latter is usually meant to be used for

new software development.

See also Win32s.

(1995-12-11)