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ZBasic Language Reference 70 ZX Microcontroller Family Sub Main() debug.print "start test" ' initialize the jump buffer Select Case SetJmp(jmpBuf1) Case 0 ' control came back from SetJmp() debug.print "calling foo()" Call foo() debug.print "normal return from foo()" Case 1 ' control came back from LongJmp() debug.print "SetJmp() returned 1 via LongJmp()" End Select debug.print "end test" End Sub Sub foo() debug.print "in foo()" Call bar() debug.print "returning from foo()" End Sub Sub bar() debug.print "in bar()" Call LongJmp(jmpBuf1, 1) debug.print "returning from bar()" End Sub Running this program will result in the following debug output: start test calling foo() in foo() in bar() SetJmp() returned 1 via LongJmp() end test Note that the last lines of neither foo() nor bar() were executed nor was the line after the call to foo() in Main(). If you comment out the call to LongJmp() in bar(), the program will produce the following debug output: start test calling foo() in foo() in bar() returning from bar() returning from foo() normal return from foo() end test Note that a call to LongJmp() generally should not utilize a value of zero as the second parameter. Doing so will make it appear as though the original SetJmp() call is returning. The jump buffer may also be a local variable if desired. The example code below is a modified version of the previous example showing how the jump buffer is passed down the hierarchy as a parameter. This technique may be used to create generalized subroutines that might return to one of several places depending on how it was called.