write a program in c

A word is said to be a doubloon if every letter that appears in the word appears exactly twice. For example, the following are all the doubloons I found in my dictionary.

Abba, Anna, appall, appearer, appeases, arraigning, beriberi, bilabial, boob, Caucasus, coco, Dada, deed, Emmett, Hannah, horseshoer, intestines, Isis, mama, Mimi, murmur, noon, Otto, papa, peep, reappear, redder, sees, Shanghaiings, Toto

Write a function called IsDoubloon() that returns TRUE if the given word is a doubloon and FALSE otherwise.