Int 2F/AX=4B02h/BX=0000h

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 PC Tools v8+ CPTASK

See Also: 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 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

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 DWORD pointer to ASCIZ task switcher name ("MS-DOS Shell Task Switcher" for DOSSHELL task switcher) 10h DWORD pointer to previous task switcher's entry point or 0000h:0000h

Format of API info structure: Offset Size Description (Table 02821) 00h WORD size of structure in bytes (000Ah) 02h WORD API identifier 0001h NetBIOS 0002h 802.2 0003h TCP/IP 0004h LAN Manager named pipes 0005h Novell NetWare IPX 04h WORD major version \ of highest version of API 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

Category: DOS-Based Task Switchers/Multitaskers - Int 2Fh - D

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