He founded Stewart Software Company there in 1984 and marketed Zilog Z80 assembly language programs, notably TOOLKIT and the ONLINE 80 Bulletin Board System, for Radio Shack TRS-80 Computers running TRSDOS.
Switching to 8088 Assembly under IBM PC DOS and MS-DOS, it released programs via shareware and commercial distribution.
Commercial products included UNIFORM, a non-destructive reformat for hard drives, CSR, which allowed service shops to archive CMOS settings from computers they serviced and restore them, and Rx, a small terminate-and-stay-resident program (TSR) which gave plain English explanations to accompany the often cryptic "Abort, Retry or Ignore?"
Stewart Computer & Supply, Inc was sold in 1993 and Stewart moved to Fort Myers, Florida where he continued to write computer diagnostic software for 8088-based machines until 1997, and was a frequent contributor to The PC Troubleshooter magazine.
Later he lived in Cape Coral, Florida where he was a ham radio operator, call sign N4CRO, a scuba diver and an amateur weather enthusiast.