From Microcontroller to Mainframe In the past 20 years I worked on systems as small as 8bit microcontrollers with no Operating System to systems as large as IBM Z-Series Mainframes. I wrote software for small FreeRTOS, Zephyr and RTEMS based controllers with only a few LED’s as “output” to GUI programs for Windows and Linux. Since low level programming has some special demands on the programming language the main languages I use, and consider myself a professional in, are C, C+