[Nition]

My memory on this is super vague because this was way back in the mists of time, but I think some old versions of DOS used to have a BASIC interpreter built in, where you could just start writing BASIC code at the DOS prompt.

[mbroncano]

QBasic was included in some of the later DOS versions.

https://en.wikipedia.org/wiki/QBasic

[TazeTSchnitzel]

There were IBM PCs with BASIC in ROM.

[khedoros1]

Some versions of DOS had a QBasic interpreter included as a utility. I stumbled upon it by accident when I was about 10 years old.