0 Function Call - Function and Recursion

Function can be called either by value or by reference .A function can be called by specifying its name followed by a list of arguments enclosed in parentheses and separated by commas.

From the above example the following line is used as a function call:

sum=add(a,b); /* function call */

Call by value: Call by value means directly pass value within the function.

An example program of call by value:

Out put of the program

Call by reference: Call by reference means sending the addresses of the argument to the called function.

In this method the addresses of actual arguments in the calling function are copied into formal arguments of the called function. (later discussed in pointer section)

The Return Statement

Information is returned from the function to the calling portion of the program via return statement.

General form of return statement:

return;

or

return(expression);

Storage Classes

There are two different ways to characterize variables:

1. By data type

2. By storage Class

Data type refers to the type of information while storage class refers to the life time of a variable and its scope within the program.

A variable in c can have any one of the four storage classes:

1. Automatic Variable:

It is created when the function is called and destroy when the function is exited. Hence the name is Automatic. By default a variable is declared Automatic.

2. External Variable:

It is also known as Global Variable. This variables can be accessed from any function that falls within their scope.

3. Static Variable:

A static variable may be either internal or external type , depending on the place of declaration.

Internal static variable extends up to the function in which they are defined and external static variable is declared outside of all function and is available to all the functions in the program.

4. Register Variable:

We can tell the compiler that a variable should be kept in one of the machine's registers, instead of keeping in the memory (where normal variables are stored ).

Since, a register access is much faster than a memory access and keeping the frequently accessed variables in the register will lead to faster execution of programs.

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