A Control Character's value can be calculated by bitwise anding the character with 0x1F.
Example: Carriage Return is a 0x0D or a control M.
M is 0x4D & 0x1F = 0x0D Voila!
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Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (5) All right, who's the wiseguy who stuck this trigraph stuff in here?