Isa_desc
extern Isa_desc *conv_isalist(void);
Isa_desc *
Isa_desc * desc;
if ((desc = calloc(1, sizeof (Isa_desc))) == 0)
static Isa_desc *isa = NULL;
extern Isa_desc *isa; /* isalist descriptor */
Isa_desc *isa = NULL; /* isalist descriptor */