Final answer:
Two probable causes for a printer printing unknown characters are corrupted or incorrect printer drivers and problems with the printer's internal memory or processing capabilities.
Step-by-step explanation:
When a printer outputs unknown characters instead of the correct document, it is likely due to one of two causes. First, there may be a communication issue between the computer and the printer, such as an incorrect or corrupted driver. Drivers are necessary for the computer to accurately translate data into a format the printer can understand. If the driver is not functioning properly, the printed result may be garbled or incorrect characters.
Secondly, the issue could be a problem with the printer's internal memory or processing capabilities, which is necessary for the accurate reproduction of documents.
If the printer's memory is insufficient or damaged, it may result in an incorrect interpretation of the document's contents, leading to the printing of unknown characters.