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Annotation of coherent/a/usr/man/ALL/portability, revision 1.1.1.1

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                      3: portability           Technical Information           portability
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                      8: Portability means that code  can be recompiled and run under dif-
                      9: ferent  computing  environments  without modification.   Although
                     10: true portability  is an ideal  that is difficult  to realize, you
                     11: can take a number of practical  steps to ensure that your code is
                     12: portable:
                     13: 
                     14:    11.
                     15:      Do not  assume that an  integer and a pointer  have the same
                     16:      size.   Remember that  undeclared functions  are  assumed to
                     17:      return an int.  If  a function returns a pointer, declare it
                     18:      so.
                     19: 
                     20:    22.
                     21:      Do not  write routines that depend on  a particular order of
                     22:      code  evaluation, particular  byte  ordering, or  particular
                     23:      length of data types.
                     24: 
                     25:    33.
                     26:      Do  not write  routines that  play  tricks with  a machine's
                     27:      ``magic  characters''; for example,  writing a  routine that
                     28:      depends on a file's  ending with <ccttrrll-ZZ> instead of EEOOFF en-
                     29:      sures that  that code can  run only under  operating systems
                     30:      that recognize this magic character.
                     31: 
                     32:    44.
                     33:      Always use  manifest constants, such  as EEOOFF, and  make full
                     34:      use of #ddeeffiinnee statements.
                     35: 
                     36:    55.
                     37:      Use header files  to hold all machine-dependent declarations
                     38:      and definitions.
                     39: 
                     40:    66.
                     41:      Declare  everything explicitly.  In  particular, be  sure to
                     42:      declare functions  as vvooiidd  if they  do not return  a value;
                     43:      this  avoids  unforeseen   problems  with  undefined  return
                     44:      values.
                     45: 
                     46:    77.
                     47:      Do not assume that  integers and pointers have the same size
                     48:      or  even the  same kind  of structure.   Do not  assume that
                     49:      pointers are  all the  same or  can point anywhere.   On the
                     50:      i8086,  in SMALL  model a  pointer  to a  function addresses
                     51:      relative to the code  segment, whereas a pointer to data ad-
                     52:      dresses  relative to  the data  segment.  On  some machines,
                     53:      character pointers are of a different size or structure than
                     54:      word pointers.
                     55: 
                     56:    88.
                     57:      The  constant NULL  is defined as  being different  from any
                     58:      valid pointer.  Use it and nothing else for that purpose.
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                     64: COHERENT Lexicon                                           Page 1
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                     69: portability           Technical Information           portability
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                     72: 
                     73: ***** See Also *****
                     74: 
                     75: header file, pointer, technical information, void
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                    130: COHERENT Lexicon                                           Page 2
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