Built‒in (Library) C Programming Functions

BUILT‒IN (LIBRARY) FUNCTIONS

The ANSI C standard library consists of wide range of C header files which can be included into a programmer's project with a single directive. Each header file contains one or more function declarations, data type definitions and macros.

The library provides a basic set of mathematical functions, string manipulation, type conversions, and file and console‒based I/O.

C language provides built‒in functions or intrinsic functions called Library Functions. The complier itself evaluates these functions. The following table shows some popular library functions.

1. sqrt(x): This function evaluates square root 'x'. Note that the argument must be non‒negative.

Example:

sqrt(25)

sqrt (b*b‒4*a*c)

Here √25 is evaluated as 5

Here √[b²‒4ac] is evaluated. If b²‒4ac is negative an error message is displayed.

2. log(x): Where the argument 'x' must be real. Here log_e x is evaluated.

Example:

log (7.5‒x*y)

Evaluate log_e (7.5‒xy)

3. abs(x): The absolute value of 'x' is the value of 'x' without sign. The abs() function evaluates the absolute value of an integer quantity.

Example: abs(‒75)

Here the absolute value of ‒75 is 75

4. fabs(x): The fabs() function evaluates the absolute value of a floating point quantity.

5. exp(x): This function evaluates e^x. Its general form is exp(). The argument x must be a real quantity. 'e' is a mathematical constant between 2 and 3.

Example: exp (7.5)

Evaluates e^7.5

6. pow(a,b): Where the arguments 'a' and 'b' are may be integer or float values. This evaluates the value of a^b.

Example: pow(3,2)

Evaluates (3)²

7. ceil(x): The argument 'x' may be integer or float. This evaluates the ceiling of the value x. Ceiling of a number 'x' is the smallest integer greater than or equal to 'x'.

Example: ceil(5.6)

Evaluates 6

8. fmod(x,y): Where the arguments may be integer or float values. This functions returns the remainder, when 'x' is divided by 'y':

Example: fmod(7,3)

Evaluates 1, because, when 7 is divided by 3 the remainder is 1.

9. rand(): This will return a random positive integer number. Note that no arguments are necessary here.

10. srand(u): Where the argument is quantity. This initializes the random number generator.

11. sin(x): This evaluates the trigonometric sine value of a real or integer quantity given in radian measure.

Example: sin(30)

Evaluates 0.5

12. cos(x): This evaluates the trigonometric cosine of a real or integer quantity. The argument 'x' must be given in radian measure.

Example : cos(30)

Evaluates the cosine value of 0.75 radians i.e., 0.866

13. tan(x): This evaluates the trigonometric tangent of a real or integer quantity given in radian measure.

Example: tan(30)

Evaluates tan(30), i.e., 0.577

14. toascii(x): Where the argument is a character or integer value. This function returns the ASCII value of the argument.

Example: toascii(a)

Evaluates 97

15. tolower(x): Where the arguments is either a character or integer value. If the argument is an alphabet, its lowercase alphabet is returned. If the argument is an integer, and it is ASCII value of the alphabet, its lower case alphabet is returned.

Example: tolower('Z')

Evaluates z

16. toupper(x): This is similar to the tolower function. This function converts small letter into the capital letter, where 'x' is a character.

Example : toupper('a')

Evaluates A