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32-bit is also a term given to a generation of microcomputers in which 32-bit microprocessors are the norm. A 32-bit register can store 232 different values. The signed range of integer values that can be stored in 32 bits is -2,147,483,648 (-1 × 231) through 2,147,483,647 (231 - 1); the unsigned range is 0 through 4,294,967,295 (232 - 1). Since 232 is 4,294,967,296, a processor with 32-bit memory addresses can directly access 4 GiB of byte-addressable memory. ==Some historical and technical perspective== Memory as well as other digital electronic circuits and wiring was expensive during the first decades of 32-bit architectures (the 1960s to the 1980s). Older 32-bit processor families (or simpler and cheaper variants thereof) could therefore have many compromises and limitations in order to cut costs. This could be 16-bit ALU, for instance, or external (or internal) buses narrower than 32 bits, limiting memory size or demanding more cycles for instruction fetch, execution and/or write back. Despite this, such processors could be labeled "32-bit" based on the fact that they still had 32-bit registers and instructions able to manipulate 32-bit quantities. As an example from the late 1970s, the original Motorola 68000 was a 16-bit based design with 32-bit registers and a 32-bit based instruction set. Such designs were sometimes referred to as "16/32-bit". However, the opposite is often true for newer 32-bit designs. For example, the Pentium Pro processor is a 32-bit machine, but the external address bus is 36 bits wide, giving a larger address space than 4 GB, and the external data bus is 64 bits wide, primarily in order to permit a more efficient prefetch of instructions and data. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「32-bit」の詳細全文を読む スポンサード リンク
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