User Defined Function :
è Users can also define
and write small program as function to do a task relevant to their programs
such function are called user defined
functions. main() as the specially recognized user define function in C.
è To use the user define
function in program need to establish following three elements:
1.
Function definition
2.
Function call
3.
Function declaration.
è Function definition is
an independent program module that is specially written to implement the
requirements of the function.
è To access the function
need to call it. It can be called at the where it needed. It is known as
function call. The program that calls the function is referred to as the
calling program or calling function.
è The declaration
specifies the prototype of function including the declaration of variable. The
calling program should declare any function that is to be used later in the program.
Function Definition
è The function definition
or function implementation shall includes following elements:
1.
function name.
2.
function type or return type
3.
parameter list
4.
local variable list
5.
function statement
6.
return statement
The general format of
function definition is as follow
return_type function_name (parameter list)
parameter declaration;
{
Local
variable declarations;
Executable
statement 1;
Executable
statement 2;
------------------
------------------
return
(expression);
}
According to the above
syntax the main elements of the function definition is grouped into two parts
1. Function header
2. Function
body
Function header
è Return type: Return type specifies
the type of returned value by function if the function does not return a value the type is
defined as void.
è Function_name : The function name is any
legal identifier followed by the parentheses
without any space in between.
è Parameter list : The parameters are given inside the parentheses
preceded by their data types & separated by commas. They serves as input
data to the function to carry out the specified task. The parameter may
declared inside the parentheses or first list them and declare them out side of
parentheses before starting the body of the function.
Function Body
è The function body contains
the declaration and statements necessary for performing the required task.
è The body enclosed in
braces, contains three parts as following
1. Local declarations
that specify the variables needed by function.
2. Executable
statements that performs the task of function.
3. A return statement
that returns the value evaluated by function. If function does not return any
value omit the return statement and must specify the return type as void.
Ex
void drawline()
{
Printf(“\n---------------------------“);
}
Function call
è A user define function
is invoked or called from the main program or any other function simply by
using the name of the function including the parentheses followed by a semi
colon.
è It contains the list of
actual parameter in parentheses.
Ex
void main()
{
printf(“\n
SMT R.O.Patel Women’s colege :”);
drawline(); // Function call
printf(“\n Morbi :”);
drawine(); // Function call
}
// function definition
void drawline()
{
printf(“\n ---------------------------------------“);
}
As shown in above example here the function drawline()
print the line on the screen & calling from main function.
Function declaration
Like variables, all
functions in a c program must be declared, before they invoked. It is also called
function prototype. They are coded in following format.
return_type
function_name(parameter list);
It is very similar to
the function header line except the terminationg semicolon
Ex,
void drawline(); // Declaration
void main()
{
printf(“\n
SMT R.O.Patel Women’s colege :”);
drawline(); // calling
printf(“\n Morbi :”);
drawine(); // calling
}
void drawline() //
Definition
{
printf(“\n
---------------------------------------“);
}
Posted By : Ruchita Pandya
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