Need basic knowledge on message digest

msg. digest is a mathematical calculation to stand for the entire file.
since its shorter theoretically (and in some MD's practically) it can occur more than once.
depending on the solution you can use SHA-1 / SHA-256 etc..

thanks kaerez, using SHA-256 solution, how can i tell if a file is message digest?

message digest is as explained.
sha-256 is one type of message digest.
if you take two programs and compute sha256 they should both provide
the same hex string.

M.D. = short representation of a long set of char.'s/string

thanks richrumble and  kaerez, this message digest is becoming more clear.  in an automatic way, how can i tell if a file has change?(monitor program)?  Do all files contain a MD5 checksum? And how do a file become MD5?

this really clear up my understanding. super thanks....

glad to be of help :-)

can you please gimme the points :-)

10x