A valid identifier in the programming language FORTAN contains a string of one to six alphanumeric characters (the 36 characters A, B,...., Z, 0, 1,...9) starting with a letter. Determine how many valid FORTRAN identifiers are there?
Ans: There are 26 letters and 10 digits a total of 36 characters. It is restricted that an identifier can be of 1 to 6 characters long only, and first character must be a letter. Thus, Total number of identifiers of length 1 = 26
Total number of identifier of length 2 = 26*36
Total number of identifier of length 3 = 26*362
Total number of identifier of length 4 = 26*363
Total number of identifier of length 5 = 26*364
Total number of identifier of length 6 = 26*365
Thus number of valid identifiers = 26*[1 + 36 + 362 + 363 + 364 + 365] = 1617038306.