Serial Output through an UART can be used to generate an immediate trace of certain performance-critical activities. If formatted debug printing is supported by the software system (as it is in Symbian OS), it is possible to output information in human readable form. This includes numeric values or strings that are in connection to the immediate situation within the system at the point the printing occurs. Serial Output is a slow way to output information, and its excessive use affects the system performance significantly. Therefore it cannot be used in order to gather large amounts of data.