The compiler can sometimes fail for very simple reasons, such as
typographical errors, including the misuse of upper- and lower-case
characters. The C language is case-sensitive. Unlike languages
such as Pascal and some versions of BASIC, C distinguishes between
upper- and lower-case letters, such as A and a. If a
letter is typed in the wrong case in a critical place in the source
code, compilation will fail. This is a potential source of errors that
are difficult to find.
