For example, a Pascal compiler ignores the case of letters in identifiers and keywords, but distinguishes them in strings.
Case insensitivity is reflected in the identity of character sequences.
In other words, the character sequences MyId , MYID and myid are considered to be identical character sequences if and only if the generated processor is insensitive to the case of letters. Since the classification and value are determined by the token processor, it is the token processor that must implement case insensitivity. The specification of each case-insensitive character sequence must invoke such a token processor. The token processor mkidn maintains a table of character sequences and provides the same classification and value for identical character sequences. Although the value of dofold could be altered on the basis of context by user-defined code, it is normally constant throughout the processor's execution.