struct	exec {	/* a.out header */	int     	a_magic;	/* magic number */	unsigned	a_text; 	/* size of text segment */	unsigned	a_data; 	/* size of initialized data */	unsigned	a_bss;  	/* size of unitialized data */	unsigned	a_syms; 	/* size of symbol table */	unsigned	a_entry; 	/* entry point */	unsigned	a_unused;	/* not used */	unsigned	a_flag; 	/* relocation info stripped */};#define	A_MAGIC1	0407       	/* normal */#define	A_MAGIC2	0410       	/* read-only text */#define	A_MAGIC3	0411       	/* separated I&D */#define	A_MAGIC4	0405       	/* overlay */struct	nlist {	/* symbol table entry */	char    	n_name[8];	/* symbol name */	int     	n_type;    	/* type flag */	unsigned	n_value;	/* value */};		/* values for type flag */#define	N_UNDF	0	/* undefined */#define	N_ABS	01	/* absolute */#define	N_TEXT	02	/* text symbol */#define	N_DATA	03	/* data symbol */#define	N_BSS	04	/* bss symbol */#define	N_TYPE	037#define	N_REG	024	/* register name */#define	N_FN	037	/* file name symbol */#define	N_EXT	040	/* external bit, or'ed in */#define	FORMAT	"%06o"	/* to print a value */