Anecdotal, but working in retail in the 90s, the backend system was some *nix server, the wireless Telxon guns ran DOS 3.2, and there was a dedicated OS/2 Warp

Anecdotal, but working in retail in the 90s, the backend system was some *nix server, the wireless Telxon guns ran DOS 3.2, and there was a dedicated OS/2 Warp desktop that would perform reporting and aggregate data. I am not sure what the registers ran, but they were IBM, all text-based. Also, I remember my friend was a manager at AMC theatres at the time, and their system was entirely text-based. I remember watching him run end-of-day reports and you could see it zip up the files and hear the modem dial out and connect to corporate.