INT 2F - DOS 5+ TASK SWITCHER - INSTALLATION CHECK                              
	AX = 4B02h
	BX = 0000h
	ES:DI = 0000h:0000h
Return: ES:DI = 0000h:0000h if task switcher not loaded
	ES:DI -> task switcher entry point (see #02819) if loaded
	    AX = 0000h
Notes:	the returned entry point is that for the most-recently loaded task
	  switcher; the entry points for prior task switchers may be determined
	  with the "get version" call (see #02819)
	this function is supported by PCIBM PC Tools v8+ CPTASK
SeeAlso: AX=4A05h,AX=4B03h


(Table 02819)
Call task switcher entry point with:
	AX = 0000h get version
		Return: CF clear if successful
			    AX = 0000h
			    ES:BX -> task switcher version struct (see #02820)
			CF set if unsupported function
	AX = 0001h test memory region
		ES:DI -> first byte to be tested
		CX = size of region to test
		Return: CF clear if successful
			    AX = memory type of tested region
				0000h global
				0001h global and local
				0002h local (replaced on session switch)
			CF set if unsupported function
	AX = 0002h suspend switcher
		ES:DI -> new task switcher's entry point
		Return: CF clear if successful
			    AX = state
				0000h switcher has been suspended
				0001h switcher not suspended, new switcher must
					abort
				0002h switcher not suspended, but new switcher
					may run anyway
			CF set if unsupported function
	AX = 0003h resume switcher
		ES:DI -> new task switcher's entry point
		Return: CF clear if successful
			    AX = 0000h
			CF set if unsupported function
	AX = 0004h hook notification chain
		ES:DI -> callback info structure to be added to chain
			  (see #02817)
		Return: CF clear if successful
			    AX = 0000h
			CF set if unsupported function
	AX = 0005h unhook notification chain
		ES:DI -> callback info structure to be removed from chain
			  (see #02817)
		Return: CF clear if successful
			    AX = 0000h
			CF set if unsupported function
	AX = 0006h query API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. support
		BX = asynchronous API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. identifier
		Return: CF clear if successful
			    AX = 0000h
			    ES:BX -> API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. info structure (see #02821) for the
				      client which provides the highest
				      level of API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. support
			CF set if unsupported function


Format of task switcher version structure:
Offset	Size	Description	(Table 02820)
 00h	WORD	major version of supported protocol  (current protocol is 1.0)
 02h	WORD	minor version of supported protocol
 04h	WORD	major version of task switcher
 06h	WORD	minor version of task switcher
 08h	WORD	task switcher ID (see AX=4B03h)
 0Ah	WORD	operation flags
		bit 0: set if task switcher disabled
		bits 1-15: reserved (0)
 0Ch	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	pointer to ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. task switcher name
		("MS-DOS Shell Task Switcher" for DOSSHELL task switcher)
 10h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	pointer to previous task switcher's entry point or 0000h:0000h


Format of API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. info structure:
Offset	Size	Description	(Table 02821)
 00h	WORD	size of structure in bytes (000Ah)
 02h	WORD	API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. identifier
		0001h NetBIOSOne of a number of low-level device-independent network interfaces; the other major interfaces are Novell's IPX and the Internet's IP (Internet Protocol, the lower-level portion of TCP/IP).
		0002h 802.2
		0003h TCP/IPThe protocol suite originally developed by DARPA for use on its ARPAnet network, which is now known as the Internet.  See also IP, TCP.
		0004h LAN Manager named pipes
		0005h Novell NetWare IPX(Internetwork Packet Exchange) A low-level layer of Novell's NetWare networking software.
 04h	WORD	major version \ of highest version of API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. for which the support
 06h	WORD	minor version / level specified in the next field is provided
 08h	WORD	support level
		0001h minimal support
		0002h API-level support
		0003h switcher compatibility
		0004h seamless compatibility