Abstract: A computer program error detection system that detects errors in a computer program by simulating execution of program statements. An internal format structure is retrieved along with a list of all functions defined by the computer program. The internal format structure is analyzed to determine all function calls and the function call ordering. External behavior models corresponding to the discovered function calls are retrieved and stored in a model table. One or more control flow paths are traversed through the computer program. For each path traversed, a structural memory model is maintained to represent the effect of the simulated execution of statements along the control flow path. A statement is simulated by executing a built in model of the operation. A function call is emulated by executing an external behavior model corresponding to the called function. Execution of an external behavior model causes the structural model memory to be updated to reflect execution of the called function.