dSpace GmbH DS1101 PCI Fixed Point Controller Board

Fixed versus Floating Point

Digital Signal Processing (DSP) can be divided into two categories, fixed point and floating point. These refer to the format used to store and manipulate numbers within the devices. Fixed point DSPs usually represent each number with a minimum of 16 bits (each digit is a bit), although a different length can be used. For instance, Motorola manufactures a family of fixed point DSPs that use 24 bits. Digital Signal Processors (DSP) have traditionally supported fixed-point arithmetic in computer hardware. But more recently, many DSP-enhanced RISC processors are starting to support fixed-point data types as part of their natural instruction (computer language) set. When the precision requirements of the application can be met with fixed-point arithmetic, then this is preferred since it can be smaller and more efficient (cost savings) than floating-point hardware.

The term floating point refers to the fact that the radix point (decimal point, or, more commonly in computers, binary point) can "float"; that is, it can be placed anywhere relative to the significant digits of the number. This position is indicated separately in the internal