Programming in C++

Prewritten Functions

C++ doesn't offer many built in keywords or functions, and that's alright because with many compilers comes standard header files. These header files contain functions that we can use to enhance our programs and not write new functions. To call a function we either use an output statement or store it in a variable. We put the function name and then enter parenthases and put in the required parameters. A parameter is what is being passed down to the function. Assuming we already initialized the variables and have the proper heading file, to call the pow function and put into a variable x would be:

x=pow(2.0, 9)

The pow will take the 2.0 and put it to the 9th power. Below is a table which lists some useful functions, the type of parameters, and which header file they're in.

Function	Header File	Purpose	Parameter(s) Type	Result
abs(x)	cmath	Returns the absolute value	int (some compilers like .NET 2005 will allow other numerical data)	int (unless other numerical data was accepted)
sin(x)	cmath	Returns the sine	double	double
cos(x)	cmath	Returns the cosine	double	double
tan(x)	cmath	Returns the tangent	double	double
pow(x, y)	cmath	Returns x to the yth power	double	double
sqrt(x)	cmath	Returns square root of x	float	float
toupper(x)	cctype	Returns the uppercase of a char	char	char
tolower(x)	cctype	Returns the lowercase of a char	char	char
clock()	ctime	Returns CPU time taken for the program to run		double
strcmp(x, y)	string	Returns int < 0 when y is < x, 0 when x and y are equal and int > 0 when x > y	string, string	int
char(x)		Returns a character	int	char
double(x)		Returns a double	int	double
rand()		Returns a random number		double

There are many more prewritten functions that come with the compilers, and many more that you can download from the web. I have just listed what I feel are the most useful prewritten functions. In the next section you'll learn how to write your own.

Next Section: Writing Your Own Functions

Free Advertising