-struct exec {
- long a_magic; /* magic number */
-unsigned long a_text; /* size of text segment */
-unsigned long a_data; /* size of initialized data */
-unsigned long a_bss; /* size of uninitialized data */
-unsigned long a_syms; /* size of symbol table */
-unsigned long a_entry; /* entry point */
-unsigned long a_trsize; /* size of text relocation */
-unsigned long a_drsize; /* size of data relocation */
-};