MELJUN CORTES C++_Functions

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USINGFUNCTIONS

IN VISUAL C++

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FUNCTION

A function is a group of computer instructionsthat performs a well-defined task inside a computerprogram.

Functions provide a way to break up a large

program into more manageable parts. Functionsalso make it possible to perform the same task atvarious points within the program without repeatingthe code.

In computer programming, functions are alsocalled subprograms. Basically, a function is aprogram by itself it may have input(s), output(s)and will perform some kind of processing steps.


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CALLING THE FUNCTION

In Visual C++ the act of transferring control to afunction is known as calling the function. When

a function is called, you supply a function name

and list of parameters, if any.


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CALLING THE FUNCTION

The following steps take place when a function iscalled:

The compiler makes a note of the location from which

the function was called and makes a copy of the

parameter list, if any.

Any storage required for the function to execute is

temporarily created.

The called function starts executing, using copies of the

data that was supplied in the parameter list.

After the function has finished executing, control is

returned to the calling function and memory used by the

function is released.


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TYPES OF FUNCTIONS

Pre-defined functions are those functionsprogrammers can already use without having to

write codes for them. Some examples of pre-

defined functions in C++ are cout and cin library

functions.

User-defined functionsare function that we are

going to write/implement by ourselves. The main()

function is a good example of a user-definedfunction although we are not limited to writing just

one user-defined function.


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USER-DEFINED FUNCTIONS

User-defined functions are group of statements that is executedwhen it is called from some point of the program. The following isits format:

type name ( parameter1, parameter2, ...) { statements }

type the data type specifier of the data returned by the

function. name is the identifier by which it will be possible to call thefunction.

parameter consists of a data type specifier followed by anidentifier, like any regular variable declaration (for example: int x)and which acts within the function as a regular local variable. They

allow to pass arguments to the function when it is called. Thedifferent parameters are separated by commas. You can use themas many as needed.

statements the function's body. It is a block of statementssurrounded by braces { }.


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// user-defined function example#include using namespace std;

int addition (int a, int b){ int r;

r=a+b;

return (r); }

int main (){ int z;

z = addition (5,3);cout



// user-defined function example#include using namespace std;

int addition (int a, int b);

int main (){ int z;

z = addition (5,3);cout



PREDEFINED FUNCTIONS

Pre-defined functions (also called built-infunctions) are stored in what we calllibraries. In C++, a library is a collection offunctions related to a particular application.

To be able to use these functions in ourprograms, we have to declare their librarythrough the #include (read as macro

include) directive.- have written by for us



STANDARD C++ LIBRARY



MATH FUNCTIONS

The C++ math functions provides quite anumber of math functions. In order to use mathfunctions, header file or isincluded into the program.



Most commonly used functions (from cmath)Funct ion s Returns Examples

abs(x) the absolute value of x abs(-12) is 12

(an int) abs(3) is 3ceil(x) the smallest integer not ceil (5.1) is 6.0

less than x ceil (-0.9) is 0.0

floor(x) the largest integer not floor (5.9) is 5.0

greater than x floor (99.99) is 99.00pow(x,y) x to the y power (x^y) pow(2,5) (=2^5) 32.0

sqrt(x) the square root of x sqrt(81) is 9.0

labs(l) the absolute value of l labs(-40000)is40000

(a long)

ceil (5.1) return 6.0

ceil (6.0)

floor(5.0) return 5.0

floor(5.9)

Except for abs &

labs, all arguments

and return values

are of type double



# include

#include

using namespace std;

int main()

{

int x;x = 2;

cout


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CHARACTER FUNCTIONS

The C++ char functions are extremely

useful for testing and transforming characters.

These functions are widely used and accepted.

In order to use character functions headerfile or is included into the

program. Some of the commonly used

character functions are:


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CHARACTER FUNCTIONS

isalnum() - The function isalnum() returns nonzero value if its argument

is either an alphabet or integer. If the character is not an integer or alphabetthen it returns zero.

isalpha() - The function isalpha() returns nonzero if the character is anuppercase or lower case letter otherwise it returns zero.

isdigit() - The function isdigit() returns nonzero if the character is a digit,i.e. through 0 to 9. It returns zero for non digit character.

islower() - The function islower() returns nonzero for a lowercase letterotherwise it returns zero.

ispunct() - The function ispunct() returns nonzero for punctuationcharacters otherwise it returns zero. The punctuation character excludesalphabets, digits and space.

isupper()- The function isupper() returns nonzero for an uppercase letterotherwise it returns zero.


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isxdigit()- The function isxdigit() returns nonzero for hexadecimaldigit i.e. digitfrom 0 to 9, alphabet 'a' to 'f' or 'A' to 'F' otherwise it returns zero.

tolower() - The function tolower() changes the upper case letter to itsequivalent lower case letter. The character other than upper case letter remains

unchanged.

toupper()-The function toupper() changes the lower case letter to itsequivalent upper case letter. The character other than lower case letter remainsunchanged.

iscntrl() - The function iscntrl() returns nonzero if the character is a controlcharacter otherwise it returns zero.

isgraph() - The function isgraph() returns nonzero if the character is anyprintable character other than space otherwise it returns zero.

isprint() - The function isprint() returns nonzero for printable characterincluding space otherwise it returns zero.

isspace() - The function isspace() returns nonzero for space, horizontal tab,newline character, vertical tab, formfeed, carriage return; otherwise it returns zero.
http://en.wikipedia.org/wiki/Hexadecimalhttp://en.wikipedia.org/wiki/Hexadecimal


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STRING FUNCTIONS

It stores a collection of functions for stringmanipulation . In order to use stringfunctions, header file or isincluded into the program.


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MELJUN CORTES C++_Functions

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