Language errors occur when the model is improperly written. This includes misspelling keywords, incorrectly ordering statements, not matching brackets. The MODEL program attempts to locate as many of these errors as possible before the model starts execution; however, some can only be detected during execution. In all cases, MODEL prints a meaningful error message, indicates the location of the error, and terminates execution. The user will then have to correct this error before running the model again.
Computation errors occur when illegal mathematical operations occur, such as division by zero. These can be corrected in one of three ways: altering the input data; altering the model to check for these conditions; and using the UNDEFVAL parameter to override these operations.