TRON is a debugging command in old dialects of the BASIC programming language. It is an abbreviation of TRace ON. It was used primarily for debugging line-numbered BASIC GOTO and GOSUB statements. In text-mode environments such as the TRS-80 or DOS, it would print the current line number which was being executed, on-screen. In a windowed environment, when the TRON command had been executed, a window would indicate the line number being executed at that instant. This command's opposite is TROFF, or TRace OFF, used to turn off command tracing.^[1]

TRON and TROFF were made obsolete by the advent of multitasking windowing environments, which permit a developer to switch back and forth between program output and source code. Modern IDEs take advantage of this to allow far more sophisticated debugging (line-by-line step-through execution of source code, examination/modification of variables, etc.). As a result, TRON/TROFF are no longer supported by most current BASIC dialects, including Microsoft Visual Basic.