apple-pascal-1.3-manual

segment numbers used by your program. Here are some things to considerwhen choosing these numbers:o They must be different from each other and different from any code ordata segment numbers used by any other Intrinsic Units accessed by thesame program.o While any program is executing, its main program uses segment 1.Therefore, never use this number for an Intrinsic Unit.o Numbers 0, 2 through 6, and 58 through 63 are reserved for use byPascal.o If you write a unit with a csegnum or dsegnum greater than 31, theprograms that use the unit must be executed under the 128K Pascalsystem.o If the program that uses the Program Unit defines any SEGMENTprocedures or functions, or uses any Regular Units, Pascal will assign anumber to each such procedure, function, or unit, starting serially from 7.These numbers must not conflict with the numbers you assign toIntrinsic Units. See Chapter 15, "Segment Numbers."o Numbers already assigned to Apple Pascal Intrinsic Units should not beduplicated, if possible. They are the following:20 TURTLEGRAPHICS (code)21 TURTLEGRAPHICS (data)22 APPLESTUFF28 CHAINSTUFF29 TRANSCEND30 LONGINTIO31 PASCALIOThe Interface SectionA Program Unit's interface section immediately follows its unit heading.This is the only part of the Program Unit that is directly accessible to theprogram that calls it. It is the part that is "visible" from the outside; itspecifies how any program that uses the unit can communicate with it. ItIII-216Chapter 12: Program Units