Refers to the number of bits that can be processed or transmitted in parallel, or the number of bits used for single element in a data format. The term is often applied to the following:
microprocessor: indicates the width of the registers. A 32-bit microprocessor can process data and memory addresses that are represented by 32 bits.
bus : indicates the number of wires in the bus. A 32-bit bus transmits 32 bits in parallel.
graphics device, such as a scanner or digital camera : specifies the number of bits used to represent each pixel. Typically 24 bits are used for color and the remaining 8 bits are used for control information.
operating system: refers primarily to the number of bits used to represent memory addresses.