i am writing udf to find concentration gradient .while compiling it is showig no error but at time of execution it is showing segementation volitation. what could be reason for this

Does it show any warning during compilation? Using a variable that is not declared correctly can result in this for example (I think), but NMAKE usually displays a warning even if it does not prevent the UDF from being compiled.

Check for the memory allocation.U might have forgot to assign memory term. DEFRINE>>>USER DEFINED MEMORY also you must have not done DEFINE__>>>>ADJUST. Check..KP