Abstract: A printer or plotter for providing printed representation of text and graphics, which further provides a specific error code signal returned to the host system. The error signals comprise fatal and nonfatal classes of system errors. The system of the data output device provides a large number of specific error conditions, to provide a specific error status indication to the system host. Upon occurrence of certain recoverable conditions for nonfatal errors, when recognized by the host system, the host computer may invoke a procedure to reset the data output device, and adjust its output data flow accordingly to provide a corrective measure in operation of the host computer with the data output device according to the present invention.

Abstract: A laser printer receiving font data and program data through removable font cartridges, which permit the user to interchange the particular font style as desired, and allows the servicing of the system by a separate maintenance program which is downloaded from the font cartridge. The laser printer sytstem includes a microprocessor which reads a particular address on the font cartridge to indicate whether the information stored thereon is font data or program information. If the information on the cartridge is a program, a subsequent font cartridge address location indicates whether an operating system or a maintenance program is resident thereon and is to be downloaded into the microprocessor system. Upon loading of such maintenance program, the maintenance operator may individually select a specific test according to a sequence of interactive system prompts.