DOS API

The DOS API refers to the Application Programming Interface provided by the Disk Operating System (DOS). It represents the collection of functions and system calls that programmers use to interact with the operating system kernel and its underlying hardware resources. These functions allow software applications to perform various tasks, such as file management, memory allocation, input/output operations, and program execution.

The DOS API is primarily accessed through software interrupts, specifically interrupt 21h, though other interrupts serve specialized purposes. By placing specific values in CPU registers before calling interrupt 21h, a program can select a particular function or service offered by the operating system. The API allows applications to control hardware through DOS, circumventing the need for direct hardware access in many cases.

The functionality exposed by the DOS API is fundamental to the operation of applications designed for DOS-based systems. It allows programs to interact with the file system, access peripherals, manage memory, and control the overall execution environment. Due to its prevalence and relative simplicity, the DOS API became a foundational element of PC programming.

The limitations of the DOS API, such as its reliance on a segmented memory model and its limited support for multitasking, eventually led to the development of more advanced operating systems like Windows and OS/2, which provided more sophisticated APIs and memory management capabilities. However, the legacy of the DOS API remains significant in the history of personal computing.