Fast Fourier Transform and Display Programmer's Reference Manual

This document is a Programmer's Reference Manual for the FFTD (Fast Fourier Transform + Display) program, designed for the 8K PDP-12B computer with EAE. The FFTD program performs Fast Fourier Transforms (FFT) and Inverse Fast Fourier Transforms (IFFT) on real or complex data sets containing 4 to 1024 points. Data can be read from and written to LAP6-DIAL, LINCtape, or disk units.

A key feature of the program is its interactive display capabilities, allowing users to visualize the real, imaginary, and magnitude components of input or output data on a scope. The display includes a moving window for larger data sets, a cursor for point inspection (showing address and value), and twelve user-modifiable scale ranges. The manual provides detailed operating procedures, including program loading, responding to system prompts, and interpreting various display modes.

Technical sections cover data storage formats, explaining that data is stored sequentially in binary files with real and imaginary parts, and outlining a pseudo floating-point data scaling method crucial for precision. The algorithm used is a modification of FFTS-C, which significantly reduces computation time compared to traditional methods. The document is categorized as "Software Support Category I," indicating it receives free support from Digital Equipment Corporation. It also includes comprehensive reference material for programmers, such as routines, subroutines, symbols, and a core chart.