- User defined functio
- Built-in function
User Defined Function
User defined function
is defined by C and C++ programmer to complete a task into a block statement.
The basic structure of a user defined function is given below.
return_data_type
function_name(argument1, argument1, …)
{
return return_value;
}
Example of a user defined function
int sum(int a, int b)
{
int c;
c=a+b;
return c;
}
In the above example,
a user defined function named sum() is declared. The sum() function accepts two
integer arguments and do summation of these
two values and then return the summation
result to the calling function.
User defined function
must be called; otherwise the function will not be executed. The function has
to be called with the following rule.
function_name(argument1, argument2, …);
According to function
calling rule, you can call the above sum() function like below.
int
sum_result=sum(10,15);
Now the sum()
function will return the summation of its argument and put the result into
sum_result variable.
User defined function
must be declared before calling function; otherwise program will show an error
message. If you don’t declare user defined function before calling, you must
declare the function prototype. The function prototype declaration rule is
given below.
return_type function_name(argument1,
argument2, …);
So, the prototype of
your sum() function will be like below.
int sum(int, int);
Example of a user defined function
without prototype
#include<stdio.h>
#include<conio.h>
//
User defined function declration
int
sum(int a, int b)
{
int c;
c=a+b;
return c;
}
void
main()
{
clrscr();
int sum_result=sum(10,15);
printf("The summation is:
%d",sum_result);
getch();
}
Example of a user define function with
prototype
#include<stdio.h>
#include<conio.h>
int
sum(int,int);
void
main()
{
clrscr();
int sum_result=sum(10,15);
printf("The summation is:
%d",sum_result);
getch();
}
//
User defined function declration
int
sum(int a, int b)
{
int c;
c=a+b;
return c;
}
Program Output
Built-in function
C/C++ provides a lot
of built-in functions which help C/C++ programmer to do their task so easily. Built-in functions are those functions whose definition is predefined and store in the header file. To use built-in function, C/C++ programmers have to know only the function name
and functionality and the header file of that function. Do Google and find required
function name and functionality and the header file that function. Now you are
able to use that function to your program. Some built-in functions those are
frequently used in C/C++ programming are given below.
printf(), cprintf(), puts(),
putchar(), scanf(), gets(), getchar(), getch(), getche(), clrscr(), abs(), sqrt(),
pow(), pow10() ,log(), log10(), sin(), asin(), sinh(), cos(), acos(), cosh() , tan(),
atan(), tanh(), rand(), arand(), randomize()
