Category: <b>DOS kernel</b>
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<pre><b>INT 21 - DOS 2+ internal - SET CURRENT PROCESS ID (SET PSP ADDRESS)</b>

	AH = 50h
	BX = segment of PSP for new process
Notes:	DOS uses the current PSP address to determine which processes own files
	  and memory; it corresponds to process identifiers used by other OSs
	under DOS 2.x, this function cannot be invoked inside an INT 28h
	  handler without setting the Critical Error flag
	under MS-DOS 3.0+ and DR DOS 3.41+, this function does not use any of
	  the DOS-internal stacks and may thus be called at any time, even
	  during another INT 21h call
	some Microsoft applications such as Quick C 2.51 use segments of 0000h
	  and FFFFh and direct access to the SDA (see <a href=../../it/87/16.html>#01687</a> at AX=5D06h) to
	  test whether they are running under MS-DOS rather than a compatible
	  OS; although one should only call this function with valid PSP
	  addresses, any program hooking it should be prepared to handle
	  invalid addresses
	this function is supported by the OS/2 compatibility box
	this call was undocumented prior to the release of DOS 5.0
SeeAlso: AH=26h,AH=51h,AH=62h
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