Standard (ISO/IEC 7185) Pascal specifies that whenever the required identifiers input and output are referenced in a program, they must appear as program parameters. When the auto-declare input and output extension is enabled, Irie Pascal does not require that input and output appear as program parameters.
For example the following program:
program hello; begin writeln('Hello!!') end.
is equivalent to
program hello(output); begin writeln('Hello!!') end.
The first program is not valid in Standard Pascal because the required identifier output is indirectly referenced by the use of the writeln procedure without specifying a file variable, but output does not appear as a program parameter.