filehdr(FP)

filehdr -- file header for common object files

Syntax

#include <filehdr.h>

Description

Every common object file begins with a 20-byte header. The following C struct declaration is used:

   struct   filehdr
   {
   unsigned short      f_magic ;        /* magic number */
   unsigned short      f_nscns ;        /* number of sections */
   long                f_timdat ;       /* time & date stamp */
   long                f_symptr ;       /* file ptr to symtab */
   long                f_nsyms ;        /* # symtab entries */
   unsigned short      f_opthdr ;       /* sizeof(opt hdr) */
   unsigned short      f_flags ;        /* flags */
   } ;

f_symptr is the byte offset into the file at which the symbol table can be found. Its value can be used as the offset in fseek(S) to position an I/O stream to the symbol table. The UNIX system optional header is 28 bytes. The valid magic numbers are given below:

   #define I286SMAGIC      0512 /* 80286 computers-small model programs */
   #define I286LMAGIC      0522 /* 80286 computers-large model programs */
   #define I386MAGIC       0514 /* 80386 computers */
   #define FBOMAGIC        0560 /* 3B2 and 3B15 computers */
   #define N3BMAGIC        0550 /* 3B20 computer */
   #define NTVMAGIC        0551 /* 3B20 computer */
   #define VAXWRMAGIC      0570 /* VAX writable text segments */
   #define VAXROMAGIC      0575 /* VAX read only sharable */

The value in f_timdat is obtained from the time(S) system call. Flag bits currently defined are:

   #define F_RELFLG        0000001 /* relocation entries stripped */
   #define F_EXEC          0000002 /* file is executable */
   #define F_LNNO          0000004 /* line numbers stripped */
   #define F_LSYMS         0000010 /* local symbols stripped */
   #define F_MINMAL        0000020 /* minimal object file */
   #define F_UPDATE        0000040 /* update file, ogen produced */
   #define F_SWABD         0000100 /* file is "pre-swabbed" */
   #define F_AR16WR        0000200 /* 16-bit DEC host */
   #define F_AR32WR        0000400 /* 32-bit DEC host */
   #define F_AR32W         0001000 /* non-DEC host */
   #define F_PATCH         0002000 /* "patch" list in opt hdr */
   #define F_80186         010000  /* contains 80186 instructions */
   #define F_80286         020000  /* contains 80286 instructions */
   #define F_BM32ID        0160000 /* WE32000 family ID field */
   #define F_BM32B         0020000 /* file contains WE 32100 code */
   #define F_BM32MAU       0040000 /* file reqs MAU to execute */
   #define F_BM32RST       0010000 /* this object file contains restore */

filehdr(FP)

Syntax

Description

See also