DOS and BASIC Data

0000:0500 - 500 Print screen status

0000:0504 - 0504 Single Drive status (A or B)

0000:0510 - 0511 BASIC's default data segment

0000:0512 - 0513 IP for BASIC's timer int. vector

0000:0514 - 0515 CS for BASIC's timer int. vector

0000:0516 - 0517 IP for BASIC's Ctl-Break int.vector

0000:0518 - 0519 CS for BASIC's Ctl-Break int.vector

0000:051A - 051B IP for BASIC's Fatal error int.vect

0000:051C - 051D CS for BASIC's Fatal error int.vect

BIOS and DOS Code

0000:0600 - start of IBMBIO.COM,IBMDOS.COM or

IO.SYS,MSDOS.SYS.