18-bit

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Processors
4-bit 8-bit 12-bit 16-bit 18-bit 24-bit 31-bit 32-bit 36-bit 48-bit 64-bit 128-bit
Applications
8-bit     16-bit     31-bit 32-bit     64-bit  
Data Sizes
4-bit 8-bit   16-bit       32-bit     64-bit 128-bit
nibble   byte   octet   word   dword   qword

In computer architecture, 18-bit integers, memory addresses, or other data units are those that are at most 18 bits (2.25 octets) wide. Also, 18-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size.

Possibly the most well-known 18-bit computer architectures are the PDP-1, PDP-4, PDP-7, PDP-9 and PDP-15 minicomputers produced by Digital Equipment Corporation from 1960 to 1975. UNIVAC also produced a number of 18-bit computers, including the UNIVAC 418 and several military systems.

18 binary digits have 262144 (1000000 octal, 40000 hexadecimal) unique combinations.

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