)
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 support
		BX = asynchronous API identifier
		Return: CF clear if successful
			    AX = 0000h
			    ES:BX -> API info structure (see #02821) for the
				      client which provides the highest
				      level of API support
			CF set if unsupported function