@section Architectures
BFD keeps one atom in a BFD describing the
architecture of the data attached to the BFD: a pointer to a
@code{bfd_arch_info_type}.  

Pointers to structures can be requested independently of a BFD
so that an architecture's information can be interrogated
without access to an open BFD.

The architecture information is provided by each architecture package.
The set of default architectures is selected by the macro
@code{SELECT_ARCHITECTURES}.  This is normally set up in the
@file{config/@var{target}.mt} file of your choice.  If the name is not
defined, then all the architectures supported are included. 

When BFD starts up, all the architectures are called with an
initialize method.  It is up to the architecture back end to
insert as many items into the list of architectures as it wants to;
generally this would be one for each machine and one for the
default case (an item with a machine field of 0). 

BFD's idea of an architecture is implemented in	@file{archures.c}.
@*
@subsection bfd_architecture

@*
@strong{Description}@*
This enum gives the object file's CPU architecture, in a
global sense---i.e., what processor family does it belong to?
Another field indicates which processor within
the family is in use.  The machine gives a number which
distinguishes different versions of the architecture,
containing, for example, 2 and 3 for Intel i960 KA and i960 KB,
and 68020 and 68030 for Motorola 68020 and 68030. 
@example
enum bfd_architecture 
@{
  bfd_arch_unknown,    /* File arch not known */
  bfd_arch_obscure,    /* Arch known, not one of these */
  bfd_arch_m68k,       /* Motorola 68xxx */
  bfd_arch_vax,        /* DEC Vax */   
  bfd_arch_i960,       /* Intel 960 */
     /* The order of the following is important.
       lower number indicates a machine type that 
       only accepts a subset of the instructions
       available to machines with higher numbers.
       The exception is the "ca", which is
       incompatible with all other machines except 
       "core". */

#define bfd_mach_i960_core      1
#define bfd_mach_i960_ka_sa     2
#define bfd_mach_i960_kb_sb     3
#define bfd_mach_i960_mc        4
#define bfd_mach_i960_xa        5
#define bfd_mach_i960_ca        6
#define bfd_mach_i960_jx	 7
#define bfd_mach_i960_hx        8

  bfd_arch_a29k,       /* AMD 29000 */
  bfd_arch_sparc,      /* SPARC */
#define bfd_mach_sparc			1
 /* The difference between v8plus and v9 is that v9 is a true 64 bit env.  */
#define bfd_mach_sparc_sparclet	2
#define bfd_mach_sparc_sparclite	3
#define bfd_mach_sparc_v8plus		4
#define bfd_mach_sparc_v8plusa		5  /* with ultrasparc add'ns */
#define bfd_mach_sparc_v9		6
#define bfd_mach_sparc_v9a		7  /* with ultrasparc add'ns */
 /* Nonzero if MACH has the v9 instruction set.  */
#define bfd_mach_sparc_v9_p(mach) \
  ((mach) >= bfd_mach_sparc_v8plus && (mach) <= bfd_mach_sparc_v9a)
  bfd_arch_mips,       /* MIPS Rxxxx */
  bfd_arch_i386,       /* Intel 386 */
  bfd_arch_we32k,      /* AT&T WE32xxx */
  bfd_arch_tahoe,      /* CCI/Harris Tahoe */
  bfd_arch_i860,       /* Intel 860 */
  bfd_arch_romp,       /* IBM ROMP PC/RT */
  bfd_arch_alliant,    /* Alliant */
  bfd_arch_convex,     /* Convex */
  bfd_arch_m88k,       /* Motorola 88xxx */
  bfd_arch_pyramid,    /* Pyramid Technology */
  bfd_arch_h8300,      /* Hitachi H8/300 */
#define bfd_mach_h8300   1
#define bfd_mach_h8300h  2
  bfd_arch_powerpc,    /* PowerPC */
  bfd_arch_rs6000,     /* IBM RS/6000 */
  bfd_arch_hppa,       /* HP PA RISC */
  bfd_arch_z8k,        /* Zilog Z8000 */
#define bfd_mach_z8001		1
#define bfd_mach_z8002		2
  bfd_arch_h8500,      /* Hitachi H8/500 */
  bfd_arch_sh,         /* Hitachi SH */
  bfd_arch_alpha,      /* Dec Alpha */
  bfd_arch_arm,        /* Advanced Risc Machines ARM */
  bfd_arch_ns32k,      /* National Semiconductors ns32000 */
  bfd_arch_w65,        /* WDC 65816 */
  bfd_arch_last
  @};
@end example
@*
@subsection bfd_arch_info

@*
@strong{Description}@*
This structure contains information on architectures for use
within BFD.
@example

typedef struct bfd_arch_info 
@{
  int bits_per_word;
  int bits_per_address;
  int bits_per_byte;
  enum bfd_architecture arch;
  unsigned long mach;
  const char *arch_name;
  const char *printable_name;
  unsigned int section_align_power;
  /* true if this is the default machine for the architecture */
  boolean the_default;	
  const struct bfd_arch_info * (*compatible)
	PARAMS ((const struct bfd_arch_info *a,
	         const struct bfd_arch_info *b));

  boolean (*scan) PARAMS ((const struct bfd_arch_info *, const char *));

  const struct bfd_arch_info *next;
@} bfd_arch_info_type;
@end example
@*
@findex bfd_printable_name
@subsubsection @code{bfd_printable_name}
@strong{Synopsis}
@example
const char *bfd_printable_name(bfd *abfd);
@end example
@strong{Description}@*
Return a printable string representing the architecture and machine
from the pointer to the architecture info structure.
@*
@findex bfd_scan_arch
@subsubsection @code{bfd_scan_arch}
@strong{Synopsis}
@example
const bfd_arch_info_type *bfd_scan_arch(const char *string);
@end example
@strong{Description}@*
Figure out if BFD supports any cpu which could be described with
the name @var{string}.  Return a pointer to an @code{arch_info}
structure if a machine is found, otherwise NULL.
@*
@findex bfd_arch_get_compatible
@subsubsection @code{bfd_arch_get_compatible}
@strong{Synopsis}
@example
const bfd_arch_info_type *bfd_arch_get_compatible(
    const bfd *abfd,
    const bfd *bbfd);
@end example
@strong{Description}@*
Determine whether two BFDs'
architectures and machine types are compatible.  Calculates
the lowest common denominator between the two architectures
and machine types implied by the BFDs and returns a pointer to
an @code{arch_info} structure describing the compatible machine.
@*
@findex bfd_default_arch_struct
@subsubsection @code{bfd_default_arch_struct}
@strong{Description}@*
The @code{bfd_default_arch_struct} is an item of
@code{bfd_arch_info_type} which has been initialized to a fairly
generic state.  A BFD starts life by pointing to this
structure, until the correct back end has determined the real
architecture of the file.
@example
extern const bfd_arch_info_type bfd_default_arch_struct;
@end example
@*
@findex bfd_set_arch_info
@subsubsection @code{bfd_set_arch_info}
@strong{Synopsis}
@example
void bfd_set_arch_info(bfd *abfd, const bfd_arch_info_type *arg);
@end example
@strong{Description}@*
Set the architecture info of @var{abfd} to @var{arg}.
@*
@findex bfd_default_set_arch_mach
@subsubsection @code{bfd_default_set_arch_mach}
@strong{Synopsis}
@example
boolean bfd_default_set_arch_mach(bfd *abfd,
    enum bfd_architecture arch,
    unsigned long mach);
@end example
@strong{Description}@*
Set the architecture and machine type in BFD @var{abfd}
to @var{arch} and @var{mach}.  Find the correct
pointer to a structure and insert it into the @code{arch_info}
pointer.
@*
@findex bfd_get_arch
@subsubsection @code{bfd_get_arch}
@strong{Synopsis}
@example
enum bfd_architecture bfd_get_arch(bfd *abfd);
@end example
@strong{Description}@*
Return the enumerated type which describes the BFD @var{abfd}'s
architecture.
@*
@findex bfd_get_mach
@subsubsection @code{bfd_get_mach}
@strong{Synopsis}
@example
unsigned long bfd_get_mach(bfd *abfd);
@end example
@strong{Description}@*
Return the long type which describes the BFD @var{abfd}'s
machine.
@*
@findex bfd_arch_bits_per_byte
@subsubsection @code{bfd_arch_bits_per_byte}
@strong{Synopsis}
@example
unsigned int bfd_arch_bits_per_byte(bfd *abfd);
@end example
@strong{Description}@*
Return the number of bits in one of the BFD @var{abfd}'s
architecture's bytes.
@*
@findex bfd_arch_bits_per_address
@subsubsection @code{bfd_arch_bits_per_address}
@strong{Synopsis}
@example
unsigned int bfd_arch_bits_per_address(bfd *abfd);
@end example
@strong{Description}@*
Return the number of bits in one of the BFD @var{abfd}'s
architecture's addresses.
@*
@findex bfd_default_compatible
@subsubsection @code{bfd_default_compatible}
@strong{Synopsis}
@example
const bfd_arch_info_type *bfd_default_compatible
   (const bfd_arch_info_type *a,
    const bfd_arch_info_type *b);
@end example
@strong{Description}@*
The default function for testing for compatibility.
@*
@findex bfd_default_scan
@subsubsection @code{bfd_default_scan}
@strong{Synopsis}
@example
boolean bfd_default_scan(const struct bfd_arch_info *info, const char *string);
@end example
@strong{Description}@*
The default function for working out whether this is an
architecture hit and a machine hit.
@*
@findex bfd_get_arch_info
@subsubsection @code{bfd_get_arch_info}
@strong{Synopsis}
@example
const bfd_arch_info_type * bfd_get_arch_info(bfd *abfd);
@end example
@strong{Description}@*
Return the architecture info struct in @var{abfd}.
@*
@findex bfd_lookup_arch
@subsubsection @code{bfd_lookup_arch}
@strong{Synopsis}
@example
const bfd_arch_info_type *bfd_lookup_arch
   (enum bfd_architecture
    arch,
    unsigned long machine);
@end example
@strong{Description}@*
Look for the architecure info structure which matches the
arguments @var{arch} and @var{machine}. A machine of 0 matches the
machine/architecture structure which marks itself as the
default.
@*
@findex bfd_printable_arch_mach
@subsubsection @code{bfd_printable_arch_mach}
@strong{Synopsis}
@example
const char *bfd_printable_arch_mach
   (enum bfd_architecture arch, unsigned long machine);
@end example
@strong{Description}@*
Return a printable string representing the architecture and
machine type. 

This routine is depreciated.
@*
