I want your opinion in my program .
My program consist of "Password.vi" this vi is going to test if the enter password is ok or not . if it is ok the "Password.vi " is going to open another vi "Sum.vi" and close the "Password.vi" .
"when the Sum.vi is open " and when i enter the value of X and Y the result didn't appear.
(LabVIEW 2015 )
In Sum.vi you set the Execution option Run when opened which is not suitable for a subvi. Remove it!
Second, in the Window Appearance properties, customize and set Show front panel when called and Close afterwards if originally closed, otherwise the front panel will not show up when Password calls Sum.
Third, as you already know how to use event structures, put your sum in an event triggered when either x or y are changed. If you want to stick polling values, don't do it at the maximum speed: you don't need to compute the sum every microsecond! Put a wait into the loop instead: a 100 ms wait should be ok, but even a 0 ms wait would help. Interactive while loops without a wait tend to suck too much processor time.
Concerning the password: what prevents the user from getting the password from the file? The user could also delete the file and get access with an empty password. As pointed out in the other thread, storing passwords in plaintext is a bad idea. Instead, store a hash of the password and compare that with a hashed version of the user input. For starters, you can use MD5 fo hashing. Although that is obsolete by modern standards, it ships with LabVIEW.