Ivor Horton is self-employed in consultancy and writes programming tutorials. He worked for IBM for many years and holds a bachelor's degree, with honors, in mathematics. Horton's experience at IBM includes programming in most languages (like assembler and high-level languages on a variety of machines), real-time programming, and designing and implementing real-time closed loop industrial control systems. He has extensive experience teaching programming to engineers and scientists (Fortran, PL/1, APL, etc.). Horton is an expert in mechanical, process, and electronic CAD systems; mechanical CAM systems; and DNC/CNC systems.