Built-in functions in C++

Library function:

• C language provides built-in functions called library function.
• The C standard library consists of a wide verity of header files which can be included in a programmer’s project with a single directive.
• Each header file contains one or more function declarations, data type definition, and macros.
• The following library functions are,

1. sqrt(x):

• This function evaluates the square root of ‘x’. Note that the argument must be non-negative.
• Example: sqrt(25)
•                 Here the square root of 25 evaluated as 5.

2. log(x):

• Where the argument ‘x’ must be real. Here log_e x is evaluated.
• Example:   log(7.5-x*y) this evaluate log_e(7.5-xy)

3. exp(x):

This function evaluates e^x. The argument must be of real quantity.

• Example:   exp(7.5) this evaluate e^7.5

4. pow(a,b):

• Where the arguments ‘a’ and ‘b’ are maybe integer or float values.
• This evaluates the value of a^b_.
• Example:   pow(4,2) this evaluate (4)².

5. ceil(x):

• It is used to rounding x to the next integer value.
• Example.    Ceil(5.6) evaluates 6

6. fmod(x,y):

• It returns the remainder of x/y.
• Example:   fmod(7,3) evaluates 1, because, when 7 is divided by 3 the remainder is 1.

7. sin(x):

• This evaluates the trigonometric sine value.
• Example:   sin(30) evaluate 0.5

8. cos(x):

• This evaluates the trigonometric cosine value.
• Example:    cos(30) evaluate 0.75

9. tan(x):

• This evaluate the trigonometric tangent(  )value.
• Example:    tan(30) evaluate 0.577

10. toascii(x):

• Returns the integer value for the particular character.
• Example:    toascii(a)     evaluates 97

11. tolower(x):

• It is used to convert the character capital letter into a small letter.
• Example:    tolower(‘Z’) evaluates z

12. toupper(x):

• It is used to convert the character small letter into a capital letter.
• Example:    toupper(‘z’) evaluates Z.

13. ctime(t):

• It is used to show the current time in your system.
• Using #include<time.h> header file and time_t datatype.       

Example program for library function:

#include<iostream.h>

#include<conio.h>

#include<math.h>//all mathematic calculations

#include<ctype.h>//to find ascii value

#include<time.h>//To display time

void main()

{

          time_t t; //time data type

          time(&t);//calling current time

clrscr();

cout<<" The current date and time is : \n"<<ctime(&t));

cout<<" The sequre root of 25 value is : \n"<<sqrt(25));

cout<<" The log(5.6) value is : \n"<<log(5.6));

cout<<" The exp(12.0) value is : \n"<<exp(12.0));

cout<<" The power 4 of 2 is : \n"<<pow(4,2));

cout<<" The round of 5.6 value is : \n"<<ceil(5.6));

cout<<" The modulo of 7/3 value is : \n"<<fmod(7,3));

cout<<" sin(90) value is : \n"<< sin(90));

cout<<" cos(90) value is : \n"<<cos(90));

cout<<" tan(45) value is : \n"<< tan(45));

cout<<" The ASCII chacter w value is :  \n"<< toascii('w'));

cout<<" The lower value of chacter H is : \n"<<tolower('H'));

cout<<" The upper value of chacter e is : \n"<<toupper('e'));

getch();

}

Output:

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