PMODE

PMODE is a DOS extender used in several IBM PC compatible DOS applications in the mid and late 1990s. It was created by Thomas "Tran" Pytel, and the first version became publicly available in 1994. The original PMODE was written to be used with programs written in x86 assembler, specifically using Borland's TASM. It was later expanded for use as a drop-in replacement for DOS/4GW under the name PMODE/W.

PMODE was released with the source code included in the distribution archive, with the only restrictions on its use being that it could not be sold for profit, nor used as the kernel of an extender to be sold for profit. Older releases also requested that the original authors be credited in the product.

The source code to PMODE/W was never made available to the public, although the extender could be used without restriction in free software, once again with a request that the authors were credited in the product. Commercial and shareware releases using PMODE/W required that a license be purchased. The cost at the time of PMODE/W v1.33's release (1996) was USD $500, although university students could purchase a license at the discounted price of USD $100.

As of 2002, PMODE/W may be freely used in commercial software, provided the software is not itself a DOS extender.

Like other DOS extenders, PMODE is used in the creation of 32-bit DOS applications that run in the protected mode of the 386+ CPU as opposed to real mode, which is the native execution mode of the DOS operating system, and the only mode of operation supported by older x86 processors (e.g. the 8086). In particular, this facilitates straightforward access to memory above 1 MB (1024^2 bytes), which cannot be addressed in real mode without special hardware, such as expanded memory boards. (In the 80286 and later processors with the A20 line enabled, segment:offset addresses allow a maximum address of 1114095 (65535*16+65535) to be specified in real mode; this extra space above 1 MB is known as the HMA, or High Memory Area.)

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