National Instruments NI-IMAQ - Manual (Page 40)

Chapter 4 Programming with NI-IMAQ for 1394 VIs
NI-IMAQ for IEEE-1394 Cameras User Manual 4-14 ni.com
code is the number identifying an error or warning. If status is
TRUE, code is a non-zero error code. If status is FALSE, code can
be zero or a warning code. Use the error handler VIs to look up the
meaning of this code and to display the corresponding error
message.
source is a string that indicates the origin of the error, if any.
Usually source is the name of the VI in which the error occurred.