Actual And Formal Arguments

Actual And Formal Arguments

The arguments may be classified under two groups, actual and formal arguments.

(a)  Actual arguments  An actual argument is a variable or an expression contained in a function call that replaces the formal parameter which is a part of the function declaration.

      Sometimes, a function may be called by a portion of a program with some parameters and these parameters are known as the actual arguments.

      For example,

             #include <iostream.h>

           void main ()

           {

                 int x,y;

                 void output (int x, int y) ; / / function declaration 

                                             

            

                  output (x,y) ; / / x and y are the actual arguments

           }

(b)  Formal arguments  Formal arguments are the parameters presents in a function definition which may also be called as dummy arguments or the parametric variables. When the function is invoked, the formal parameters are replaced by the actual parameters.

     For example,

          #include <iostream.h>

         void main ()

           {

                 int x,y;

                 void output (int x, int y) ;

                output (x,y) ;

           }

           void output (int a, int b)  / / formal or dummy arguments

           {

                   / /body of the function

           }

  Formal arguments may be declared by the same name or by different names in calling a portion of the program or in a called function but the data types should be the same in both blocks.

For example, the following function declaration is invalid.

       #include <iostream.h>

      void main ()

      {

            void funct (int x, int y, char s1, char s2) ;

            int x,y;

            char s1, s2;

                         

               funct (x,y,s1,s2) ;

      }

      funct (char c1, char c2, int a, int b) / / data type mismatch

      {

             / / body of a function

      }