110179 Fast Fourier Transform Routine Version: February 1975 Submitted by: Digital Equipment Corporation Source Language: MACRO-11 Keywords: Scientific Applications Abstract: FFTR is a PDP-11 assembly language subroutine which performs a 16-bit precision forward or inverse Fast Fourier Transform of N real-valued data points, where N is a power of 2 in the range 16 less than or equal to N less than or equal to 2048. A sample size of 2048 points if transformed in 1.21 seconds on a PDP-11/20 with EAE. Accuracy is preserved by scaling only when overflow occurs. FFTR requires about 1400 words of memory, exclusive of the user supplied N+2 word buffer. It can be called from FORTRAN under DOS or RSX-11D/M or linked with an assembly language program. Versions are available for all PDP-11's and no hardware arithmetic unit is required. However, use of a hardware arithmetic unit greatly improves the speed of FFTR and special versions of the routine are available for machines which are equipped with EAE or EIS. Documentation available in hardcopy only. Media (Service Charge Code): Write-Up (AA), One RX01 Diskette (KA) Format: RT-11, 600' Magnetic Tape (MA) Format: DOS-11