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RADIX-50 is a coding system much used by DEC, particularly in PDP-11's, to hold alphanumeric data in a fairly space-minimal form. It could hold 3 characters in a single 16-bit word. Individual characters were not stored in separate bit fields within the word; rather, a multiplication and addition process was used to combine them.

The character set supported included the characters ' ' (encoded as 0), '$' (27.), '.' (28.), and '_' (29.; sometimes replaced by '%'), the upper-case letters (1-26), and the decimal digits (30.-39.). 40 different values in total, or 050 - hence the name. To combine the three characters, the first was multiplied by 050, added to the second, and the result multiplied again, to which was added the third.