## Physical Device Driver Reference

[prev][next][parent][TOC]

### Physical Device Driver Overview

OS/2 physical device drivers are different from DOS device drivers and DOS terminate and stay resident (TSR) programs. All three of these types of software handle I/O requests for applications in their respective environments but because the environments are so different between DOS and OS/2, the responsibilities of the software doing the I/O are very different also.

For example, DOS is a single-tasking environment where software spins the CPU waiting for I/O to complete and can do this because there is only one task running. OS/2 is a multitasking operating system where the CPU is freed to dispatch other tasks if one task is waiting for I/O to complete. DOS runs in the real mode of the 80x86 processor. OS/2 runs in the protected mode of the 80x86 processor.