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Next: Functions that return values
Up: Introduction to User-defined functions
Previous: Functions with no parameters
The function of the previous section is not very useful, what if four lines were to be skipped, or two lines? It would be much more useful if it was possible to tell the function how many lines to skip. That is the function should have an input parameter which indicates how many lines should be skipped.
The function skipthree() is now changed to the function
skip which has a parameter
n indicating how many lines have to be skipped as follows:
void skip(int n)
// Function skips n lines on output
{
int i; // a local variable to this function
// now loop n times
for (i = 0; i < n; i++)
cout << endl;
}
Download program.
As before this function does not return a value hence it is declared
as having type void. It now takes an integer parameter
n which indicates the number of lines to be skipped. The
parameter list then consists of a type and a name for this formal
parameter. Inside the body of the function (enclosed in {}) a
loop control variable i is declared. This variable is a
local variable to the function. A local variable defined
within the body of the function has no meaning, or value, except
within the body of the function. It can use an identifier name that
is used elsewhere in the program without there being any confusion
with that variable. Thus changing the value of the local variable
i in the function skip will not affect the value of any other
variable i used elsewhere in the program. Similarly changing
the value of a variable i used elsewhere in the program will
not affect the value of the local variable
i in skip.
The function is called in the same manner as skipthree() above,
but a value must be given for the parameter n. Thus all the
following calls are acceptable:
void main()
{
int m = 6, n = 3;
...............;
skip(m);
.......;
skip(m + n);
............;
skip(4);
.......;
}
however the call:
skip (4.0);
would not be acceptable because the actual parameter type
must match the formal parameter type given in the definition
of the function.
In writing the function prototype for a function with parameters it is
not necessary to detail the formal names given to the parameters of the
function, only their types. Thus a suitable function prototype for the
parameterised version of skip would be:
void skip(int); // function prototype