hi, I am a star-cd v3.24 user and I want to save my file on previous vesion, which command should I use? can you help me... thanks

you can always do a 'save coded'

this generates you a couple of files and an input file (*.inp). This input file you can read in previuos versions of prostar via the read file option.

Normally this works fine. There might be some minor problems, e.g. when you defined turbulence model in V3.24 which is not available in older version. So you should check you settings afterwords.