Counting variables in BASIC
The name of a variable in BASIC is a string of one or two alphanumeric
characters (lowercase English letters and decimal digits). Moreover, a
variable name must begin with a letter and must be different from the
five strings of two characters that are reserved for special purposes.
How many different variable names do we have?
V - the number of all variable names
V1 - the number of 1-character names
V2 - the number of 2-character names
V = V1+ V2 (by the sum rule)
V2 = 26 ? (26+10) - 5 = 931