Help with C program algorithm

I'm attempting to write a program in C in which When given a set of letters the program searches a dictionary of words to find all the words that can be made from those letters and outputs those words. Each letter
can be used at most once and the underscore ("_") can stand for any single letter.

For example, given
the set of letters aert_ , the words output may include
ARE
AREa
AT
ATE
EAT
mATE
RAT
RATE
REAd
TEAR
TRAdE
TREAd
Where blanks are printed in lower case.

I thought it would be simple enough, but I'm having problems developing an algorithm that allows for the output of all the word variations. For example, matching the entered characters so that the search allows RATE and TEAR to be output.
Any suggestions on how to start?

Chris

this can be simply done by
1. taking string length of no the string u'll enter

Eg if u enter: arsd_

by using strlen function calculate the string lenght.

next step...
u need an external file with all these words u wanna find

then do a simple search of words and then with simple if else condition u'll manage that...

PS: i m presuming that u r good at programming