When this extension is enabled (it is by default), the Irie Pascal compiler will automatically declare the built-in identifiers input and output, when they are not declared in your program.
Standard Pascal (i.e. ISO/IEC 7185) specifies that whenever the required identifiers input and output are referenced in a program, that they must by declared (i.e. appear as program parameters). However because some Pascal compilers do not enforce this requirement many Pascal programs do not meet this specification. NOTE: ISO/IEC 7185 is the standard for the Pascal porgramming language published by the Internation Organization for Standardization.