Pascal III: Comparison to Apple II Pascal (1 of 2)

Pascal III: Comparison to Apple II Pascal (1 of 2)

The majority of Apple II Pascal programs can be recompiled then executed on
the Apple III without modification.  The following is summary of significant
differences between Pascal II and Pascal III.  Please refer to the Apple III
Pascal Programmer's Manual, Volume 2, starting on page 128, for additional
information.
 
OTHERWISE Clause in CASE Statement:
 
Pascal III provides an OTHERWISE clause in the CASE statement.  The
OTHERWISE clause allows you to enter a statement that is executed if none
of the cases are executed.  Refer to chapter 5 of the Apple III Pascal
Programmer's Manual.
 
SOS Pathnames:
 
SOS Pathnames are different from the Pascal filenames used on the Apple II.
Pascal III supports both types of names, as explained in the Apple III Pascal
Introduction, Filer, and Editor manual.
 
SOS Device Driver Support:
 
Pascal III supports SOS device drivers as "I/O units."  See Chapters 10 thru
12 in the Standard Device Drivers Handbook.
 
Graphics:
 
The Apple III screen graphics modes driven through the SOS graphics driver
differs significantly from the Apple II.  Therefore, a new unit named PGRAF
is supplied as a high-level interface to the graphics driver.  Refer to the
Standard Device Driver manual for additonal information on the SOS graphics
driver.
 
Turtlegraphics is available only for compatibility with the Apple II.  Refer
to Appendix K of the Apple III Pascal Programmer's Manual.
 
 
New Procedures:
 
The AppleStuff unit contains Date, TimeOfDay, ClockInfo, and SetTime
procedures for reading and setting the Apple III system's internal date and
time.  See Appendix D of the Apple III Pascal Programmer's Manual.
 
New Data Types:
 
The ByteStream and WordStream types are provided for use as types of Var
parameters in procedure and function definitions. See Chapter 3 of the
Apple III Pascal Programmer's Manual.
 
Real Arithmetic:
 
For operations on type Real values, Pascal III conforms to the IEEE
floating-point standard.  Under default conditions, the difference between
the Pascal III and Apple II Pascal is invisible, unless the program performs
operations giving execeptional results, such as division by zero. See
Appendix F of the Apple III Pascal Programmer's Manual for complete details.
 
The Apple Pascal Numeric SANE package, available for both the Apple II and
Apple III, establishes a universal mathematic environment for the two systems.
 
Library Files and Units:
 
Each Pascal III codefile can have a "program library" file associated with
it in addition to the System.Library file.  Thus, library units are more
convenient; furthemore, programs may have up to 48 segments at run time.
 
When compiling a unit, it is no longer necessary in all cases to use the
Compiler's swapping option.