Prime Factor FFT
Fast Fourier Transform (FFT) Analysis Subroutine Library for Windows and DOS


Prime Factor FFT image

DOS Version Only:

Windows DLL Version Only:


Prime Factor FFT is a subroutine library for developing digital signal processing and spectral analysis applications. Callable from any language, Prime Factor FFT is available for Windows as a dynamic link library (DLL) or for PCs running DOS.

Written in assembly to assure fast execution, Prime Factor FFT includes highly optimized functions for calculating complex forward and inverse FFTs in 1-D and 2-D. For example, Prime Factor FFT is capable of performing a 1,008-point FFT in 30 ms on a 66-MHz 486 PC and performing even faster on a Pentium-based computer.

Prime Factor FFT is ideal for scientists and engineers with modest programming experience and for applications requiring the analysis of time-domain signals in the frequency domain.

DLL Version for Windows 3.1 (16-Bit)

Prime Factor FFT is now available as a dynamic link library (DLL) for Windows. The functions in this version can be called from any application that can access a Windows DLL. Features of Prime Factor FFT for Windows include compatibility with any compiler, the ability to transform any data type array of any length up to available memory, a re-entrant design for simultaneous use of the library in multiple applications, and example call programs written with Visual Basic and Visual C++. The Windows version also includes three algorithms, including a discrete Fourier transform (DFT), for matching the fastest algorithm to a particular data set size.

High-Speed Calculations


(66-MHz 486 PC)


8 ms


30 ms 


55 ms


110 ms


225 ms 


513 ms 

Prime Factor FFT automatically detects the math coprocessor type at runtime, enabling the code to run faster by using the extended instruction set of the detected coprocessor. Prime Factor FFT also does not perform time-consuming trigonometric calls, further ensuring fast FFT calculations.

Data Analysis

Both the DOS and Windows versions of Prime Factor FFT eliminate the need to add artificial data or truncate the size of data to from test arrays to meet one of 16, power of 2 size requirements. The DOS version uses the prime factor algorithm to make available 815 data set size choices up to 64,600 data points in 1D data and 664, 225 data set size combinations up to available memory in 2D data. The Windows version also includes a discrete Fourier transform (DFT) for analyzing any data set size not supported by the prime factor and Cooley-Tukey algorithms.

In addition, Prime Factor FFT performs transparent data analysis in the background, saving processing time by allowing other tasks to operate simultaneously in the foreground.

Sample Programs

Prime Factor FFT is shipped with example applicationprograms using the most popular compilers. These programs provide a template for an application and include sample code that can be pasted into the application source code to meet specific requirements.

DOS version:  Provides sample programs for Microsoft C, Turbo C, Quick BASIC, Turbo BASIC, Turbo Pascal, and Microsoft Fortran

Windows version: Provides sample programs for Visual Basic and Visual C++

If you have a language not listed above, contact the factory.

System Requirements

For Windows DLL Version:  IBM PC/AT, 386, 486, Pentium or compatible computer. Microsoft Windows 3.0 or higher; DOS 3.0 or higher; math coprocessor for 386 and 486SX-based machines. 4 MBytes of RAM recommended for large data set sizes

For DOS Version: IBM PC/AT, 286, 386, 486, Pentium or compatible computer; 512Kbyte DOS memory; DOS 3.0 or higher; math coprocessor for 286, 386, 486SX-based machines; hard disk; high density floppy drive.

Multi-User Licenses

Run-Time License* - Alligator Technologies offers run-time licenses on Prime Factor FFT. The license is an attractive option if Prime Factor FFT will be used by many users at a single site or if the subroutines will be integrated into an application program for resale.

Royalty Agreement - Alligator Technologies offers a royalty license agreement that is based on a quarterly fee, not on a charge per distributed copy. This agreement is designed to reduce the cost per copy as the number of units sold increases. A fee is charged either per year or per quarter, which starts on the first day of the month of either January, April, July, or October.

Customer Support

Each copy of Prime Factor FFT is backed by free technical phone support, an unlimited lifetime warranty, and a 30-day money back guarantee. Registered users also qualify for reduced-price product upgrades.

A user manual provides documentation on applying Fourier theory as well as lists all of the library's functions and their usage.

* For information on multi-user licenses, call Alligator Technologies or your local Alligator distributor.

How to Order


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