It's PL/I, promoted by IBM as the successor to FORTRAN, Algol 60, and COBOL. That's actual code as far as I recall, not pseudocode.
PL/I had abbreviations for keywords; "DCL" is "DECLARE".
It starts off by defining a procedure (routine) named P with one parameter, named MODE, which is a Boolean variable - BIT(1), then defines a bunch of 16-bit signed integers allocated on the stack, and some statically-allocated arrays.