From ArticleWorld

PL/C is a subset of the IBM PL/I language designed at the Cornell University in the early 1970s. It did not include the more complex features of PL/I, and was mainly intended to be a teaching language.

PL/C was notable for its advanced automatic syntax error correction. This made PL/C compile literally any program, by correcting any obvious syntax errors and turning anything that could not correct to simple output statements.

Except for this notable feature, PL/C was never too popular, not even as an educational language. The automatic error corrector would often fail, detecting errors correctly but not fixing them as it should have, generating even more errors than it corrected. The fact that it turned errors to output statements when it could not correct them was not very intuitive either, as debug statements often got garbled or useless.

PL/C wasn't too widely used outside the Cornell University. However, it remains a notable programming language because it was the first one to try an alternative to the usual write-compile-fix-run cycle. It was also a programming language that tried to simplify the PL/I without losing its initial scope.