The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295 or −2,147,483,648 through 2,147,483,647 using two's complement encoding. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory.
The external address and data buses are often wider than 32 bits but both of these are stored and manipulated internally in the processor as 32-bit quantities. For example, the Pentium Pro processor is a 32-bit machine, but the external address bus is 36 bits wide, and the external data bus is 64 bits wide.
Prominent 32-bit processors include the Intel 80386, Intel 80486, and Pentium series, and the Motorola 68000 series. The Motorola 68000 is externally 16 bits long; however, it has 32-bit general purpose registers, arithmetic units, and is forwards-compatible with all 32-bit software.