This section documents the services that the MS-DOS kernel provides to application programs via software interrupts 20H—2FH. Each MS-DOS function is described in the same format:
A heading containing the function's name, software interrupt and function number, and an icon indicating the MS-DOS version in which the function was first supported. You can assume that the function is available in all subsequent MS-DOS versions unless explicitly noted otherwise.
A synopsis of the actions performed by the function and the circumstances under which it would be used.
A summary of the function's arguments.
The results and/or error indicators returned by the function. A comprehensive list of error codes can be found in the entry for Int 21H Function 59H.
Notes describing special uses or dependencies of the function.
A skeleton example of the function's use, written in assembly language.
Version icons used in the synopsis, arguments, results, or Notes sections refer to specific minor or major versions, unless they include a + sign to indicate a version and all subsequent versions.
For purposes of clarity, the examples may include instructions that would not be necessary if the code were inserted into a working program. For example, most of the examples explicitly set the segment registers when passing the address of a filename or buffer to MS-DOS; in real applications, the segment registers are usually initialized once at entry to the program and left alone thereafter.