PLOT3D was created by NASA Ames Research Center in 1982 by Pieter Buning[1] and remains an often used file format.
This makes it simple to iterate through a series of volumetric elements and calculate all required properties for the purpose of a CFD analysis.
[2] Data may be stored in either binary or ASCII text format and floating point values may be either single or double precision.
"Unformatted" FORTRAN (binary) files have the variables laid out in the same order but will normally lack delimiters such as line breaks.
[4] A multiblock, 3 dimensional grid file begins with a single integer for the number of blocks M on its own line.
[5] Additionally, the format may be simplified such that only a two-dimensional problem is analyzed or the iBlank parameter is omitted.