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 General
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 Since DOS extended programs run in protected mode, they automatically
 benefit from the extra checking performed by the processor in protected
 mode. Errors such as segment overruns, invalid pointers and the like are
 immediately detected, and a general protection fault is issued.

 With the exception of CA-Clipper, which has its own source level debugger
 (see below), system level debuggers such as NuMega SoftICE/W and Periscope
 for Windows are required for source level debugging of DOS extended
 programs. Both these products can also be used to debug Windows and real
 mode DOS programs, so provide a single debugging interface for all three
 environments.

 When running without a debugger, a protection fault, such as an invalid
 pointer, is passed to the default handler inside the DOS extender. This
 handler dumps out all the registers, the code being executed and the stack
 context and then returns to DOS. This dump is sent to the standard output
 device, so can be redirected to a file on the program's command line for
 analysis if required, e.g.:

 TEST > TEST.GPF
 The section below entitled `General protection fault (GPF) analysis'
 contains a detailed discussion of how to analyse the output from a general
 protection fault.

 CA-Clipper 5.x note

 The CA-Clipper 5.x debugger can be used in protected mode by linking it into
 the program. This is done by adding the command:

 FILE <path>CLD.LIB

 to the end of the link script file. It may be necessary to specify a path
 for the file if it is not in the current directory. At runtime the debugger
 is called by pressing Alt-D or by inserting the ALTD() function call in the
 code.

 The standalone debugger CLD.EXE is not protected mode compatible, and so
 cannot be used to debug protected mode programs.