What are actual and formal parameters?

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Actual Parameters: Actual parameters are the variables or expressions referenced in the parameter list of a subprogram.

Let’s see a procedure call which lists two actual parameters named empno and amt:

raise_sal(empno, amt);
Formal Parameters: Formal parameters are variables declared in a subprogram specification and referenced in the subprogram body.

Following procedure declares two formal parameters named empid and amt:

PROCEDURE raise_sal(empid INTEGER, amt REAL) IS current_salary REAL;