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OS_UpCall 256
Programmer's Reference Manuals
» Part 15 – SWI Calls
» OS
» OS_UpCall
» OS_UpCall 256
OS_UpCall 256
(SWI &33)
| Entry | |
|---|---|
| R0 | 256 (&100) |
| R2 | Currently active object Pointer |
| Exit | |
|---|---|
| R0 | 0 to stop application, else R0 is preserved |
| R2 | Preserved? |
Use
The purpose of this call is to call inform your application that a new application is going to be started.
Notes
This call is made just before a new application is going to be started in the current application space – for example due to a *Run or module command. It calls the UpCall vector.
One reason to use this call is so that an application can tidy up itself before a new one is started, e.g. removing routines from vector.
Another reason to use this UpCall is to prevent an application from starting. If you don’t want the application to start, your routine should set R0 to 0, and intercept the call to the vector. This will cause the error ‘Unable to start application’ to be given. Otherwise, you must pass the call on with all registers preserved.