Fast Fourier Transform and Display

This document details the Fast Fourier Transform + Display (FFTD) program, designed for the 8K PDP-12B computer with Extended Arithmetic Element (EAE). The program performs Fast Fourier Transforms (FFT) or Inverse Fast Fourier Transforms (IFFT) on data sets ranging from 4 to 1024 real or complex points. Data can be loaded from and stored on LAP6-DIAL, LINCtape, or disk units.

Key features include interactive scope displays that show the real and imaginary components, as well as the magnitude, of input and output data. These displays offer a movable window for larger data sets, a cursor that provides detailed information about specific data points (memory address, content, Y coordinate), and user-adjustable scaling for the Y-axis across twelve different ranges. All calculations use single-precision fixed-point signed binary fractions, employing a variable scale factor to preserve precision. The FFT algorithm used is a modification of FFTS-C, significantly reducing computation time compared to older methods.

The manual provides comprehensive operating procedures for loading the program, specifying input/output data sources and formats, selecting transform or display modes, and interacting with the various display options. It also covers data storage conventions and lists the subroutines utilized for tape/disk manipulation, user interaction, and algorithm execution.