Sometimes, as a program runs, it drops out with a message BDOS ERROR BREAK IN (various numbers). After this, either the program proceeds after a return or the entire machine is locked up. This happens at infreqent intervals on many other Apple IIIs and other Softcards. It may seem that the problem is hardware-related, but in fact BDOS ERRORS are usually caused by the CP/M software when it attempts to access a device that is not ready or not on line. In the most common situation, the program tries to read a non-existent disk drive; this reports a BDOS ERROR ON xx: SELECT. Typing a RETURN should return you to the system prompt, and typing an 'R' will retry the last command. The BDOS ERROR BREAK message example above is from MBASIC and refers to the fact that the program attempted to access a device that is not ready or on line; the number in the message is the line number of the MBASIC statement which tried the read. To avoid this message, use the ON ERROR GOTO statement to branch to statements that display instructions to ready the device or put it on line.