16-bit microprocessors

In computer architecture, 16-bit integers, memory addresses, or other data units are those that are 16 bits (2 octets or 2 Bytes) 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 microcomputers are computers in which 16-bit microprocessors were the norm.

As n-bit register can store 2ⁿ different values. So as a result, 16-bit register can store 2¹⁶ different values. If we consider the signed range of integer values that can be stored in 16 bits is −32,768 (−1 × 2¹⁵) through 32,767 (2¹⁵ − 1). But on the other hand in case of unsigned range is 0 through 65,535 (2¹⁶ − 1). Since 2¹⁶ is 65,536, a processor with 16-bit memory addresses can directly access 2¹⁶ = × 2⁶ × 2¹⁰ = 64 x 1024 = 64 x 1K = 64 KB (65,536 bytes) of byte-addressable memory. If a system uses segmentation with 16-bit segment offsets, more can be accessed.

In the year 1978, Intel introduced the 16-bit microprocessor 8086 (16-bit bus) and in the year 1979, Intel introduced 8088 (8-bit bus). It had 29,000 transistors. In the year 1981, IBM selected the Intel 8088 for their personal computer (IBM-PC). In the year 1982, Intel released the 16-bit microprocessor 80286 (having 1,34,000 transistors) to be used for the advanced technology personal computers (PC-AT) as CPU. It was called Intel 286 and was the first Intel processor that could run all the software written for its predecessor Intel 8088. To have the great commercial success, this backward software compatibility was important. It is important to note that this software compatibility remains a hallmark of Intel's family of microprocessors.