25 Years of Programming
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Function library for the Heathkit H-100 computer in DeSmet C

DeSmet C is still available free on the internet. If you have an old H-100 (or Zenith Z-100) computer and want to do something interesting with it, DeSmet C is a good way to go.

I was limited to using GWBASIC for graphics programming until I wrote my PSET function and the others that it made possible. The assembly language optimization of PSET was a major triumph. One of the few projects I ever did in assembly language, it made H-100 color graphics incredibly fast by H-100 standards and made it possible to do any graphics programming I wanted, free from GWBASIC.

In addition to the functions listed on this page, there are Borland C++ functions that I originally wrote in DeSmet C and that might be converted back to it without too much difficulty.

Each link below goes to the project page, which has a more complete description and code listings.

PSET: Color Graphics Primitive Functions	Color graphics primitives for pixel manipulation, in .C and .A (optimized assembler). pset(): get pixel color, set pixel color, using OR, XOR, and other options.
Color Graphics Drawing Functions	Drawing functions: line(), box(), circle().
Paint (Flood Fill) Function	Paints an enclosed graphic area with specified color or combination of colors, using regular or random tiling, within a specified border color or to edge of screen.
Graphics Bitmap Save/Load Functions	Fast routines to save color screen display to a disk file, and load back in.
Two-page Video Management Functions	The H-100 has 2 video pages! You can independently choose which page you draw to and which page is displayed.
Display Management Functions	Display management functions, using the H-19 / H-89 / H-100 terminal escape codes.
Procedural Utility Functions	abort() terminates program execution.
Random Number Functions	Two random number related functions, one a bug fix for DeSmet C.
Input Functions	contin() asks "Do you want to continue?", presskey() says "Press any key to continue...", two input functions allow for a default value if user just presses CR, and a function that emulates the BASIC function INPUT #1, A$.
String Search Function	A string search function that emulates the BASICA INSTR function.
Date and Time Routines	Miscellaneous date and time routines.