Batch files on MS-DOS 3.2 (on a Tandy 1000 SX). My second programming language was BASICA, on that same machine.
The 1000 SX came with MS-DOS 3.2 and Deskmate 2 on 5.25" 360K diskettes. The MS-DOS was a version specialized for and only bootable on the Tandy 1000, as it would announce on the screen of any other PC-compatible one tried to boot with it; it included a version of BASICA (Microsoft's Advanced GW-BASIC) with support for the enhanced CGA graphics modes (a.k.a. Tandy Graphics or TGA) and three-voice sound hardware of the Tandy 1000.
Ah, the good old days, when 640K really was enough for anybody...