16-bit

In computer architecture, 16-bit integers, memory addresses, or other data units are those that are at most 16 bits (2 octets) wide. Also, 16-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size. 16-bit is also a term given to a generation of microcomputers in which 16-bit microprocessors were the norm.

A 16-bit register can store 2¹⁶ different values. The signed range of integer values that can be stored in 16 bits is -32,768 (-1 × 2¹⁵) through 32,767 (2¹⁵ - 1); the unsigned range is 0 through 65,535 (2¹⁶ - 1). Since 2¹⁶ is 65,536, a processor with 16-bit memory addresses can directly access 64 KiB of byte-addressable memory.

16-bit architecture

The MIT Whirlwind (c. 1951) was quite possibly the first-ever 16-bit computer. Other early (c. 1965–70) 16-bit computers include the IBM 1130, the HP 2100, the Data General Nova, and the DEC PDP-11. Early (c. 1973–75) multi-chip 16-bit microprocessors include the National Semiconductor IMP-16 and the Western Digital MCP-1600. Early (c. 1975–76) single-chip 16-bit microprocessors include the National Semiconductor PACE, the HP BPC, and the TI TMS9900. Other notable 16-bit processors include the Intel 8086, the Intel 80286, the WDC 65C816, and the Zilog Z8000. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16 bits long and arithmetic instructions, even though its external bus was 8 bits wide.