Chapter 8 Interrupt 21h Functions

8.1 Introduction

This chapter describes the MS-DOS functions that a program can call to manage system operation and resources. Using these functions makes it easier to write computer-independent programs and increases the likelihood that a program will be compatible with future versions of MS-DOS.

Programs use MS-DOS services by issuing software interrupts. Interrupt 21h is the function request service; it provides access to a wide variety of MS-DOS services. Each function request uses values in various registers to receive or return function-specific information.