![]() ![]() The IBM 1400 series are character-addressable machines, each location being six bits labeled B, A, 8, 4, 2 and 1, plus an odd parity check bit ( C) and a word mark bit ( M). ![]() Burroughs systems used 1101 (D) for negative, and any other value is considered a positive sign value (the processors will normalize a positive sign to 1100 (C)). These match the EBCDIC zone for digits without a sign overpunch. ILE RPG uses 1111 (F) for positive and 1101 (D) for negative. Most implementations also provide unsigned BCD values with a sign nibble of 1111 (F). IBM System/360 processors will use the 1010 (A) and 1011 (B) signs if the A bit is set in the PSW, for the ASCII-8 standard that never passed. Other allowed signs are 1010 (A) and 1110 (E) for positive and 1011 (B) for negative. This convention comes from the zone field for EBCDIC characters and the signed overpunch representation. Standard sign values are 1100 (hex C) for positive (+) and 1101 (D) for negative (−).
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