les di, NewService ;new address of service-function handler
mov ax, 0003h ;Resume Switcher
call [Service] ;Service-function handler
jc error_handler
Resume Switcher (Function 0003h) notifies a suspended task switcher that it can resume operation.
Client programs must not call this function.
NewService
Points to the new task switcher's service-function handler. The task switcher that is being resumed can use this address to call the new task switcher's service functions, such as Get Version (Service Function 0000h).
If the function is successful, the carry flag is clear and the AX register contains 0000h. If the task switcher does not support this function, the carry flag is set.
A task switcher that has disabled another task switcher by using Suspend Switcher (Service Function 0002h) should call Resume Switcher to reenable it, and should use the same service-function-handler address that it used to call Suspend Switcher.
A task switcher processing Resume Switcher can enable interrupts and call any MS-DOS system function. Although the task switcher modifies the AX register, it must preserve all other registers.
Service Function 0000h Get Version
Service Function 0002h Suspend Switcher