data formats -- Definition

Mark Williams  Company has  written C compilers  for a number  of different
computers.  Each has a unique  architecture and defines data formats in its
own way.

The following  table gives the sizes,  in chars, of the  data types as they
are defined by various microprocessors.


            i8086 i8086
Type i80386 SMALL LARGE Z8001 Z8002 68000 PDP11  VAX
char    1     1     1     1     1     1     1     1
double  8     8     8     8     8     8     8     8
float   4     4     4     4     4     4     4     4
int     4     2     2     2     2     2     2     4
long    4     4     4     4     4     4     4     4
pointer 4     2     4     4     2     4     2     4
short   2     2     2     2     2     2     2     2

COHERENT places  some alignment restrictions on data,  which conform to all
restrictions  set  by the  microprocessor.   Byte ordering  is  set by  the
microprocessor;  see   the  Lexicon  entry   on  byte  ordering   for  more
information.

Please  note  that  Intel  processor  documentation  and the  Intel  Binary
Compatibility  Standard  (iBCS2)   use  the  term  word  differently.   The
following table defines how they differ:

Bytes               1         2         4         8
Bits                8        16        32        64
Intel             byte      word      dword     qword
iBCS2             byte    halfword    word   doubleword

See Also

byte ordering,
C language,
data types,
double,
float,
float.h,
Programming COHERENT

Notes

COHERENT 286  supports Intel SMALL  model only.  COHERENT  386 supports the
i80386 data format.

© 2012 by Stephen A. Ness