=== Library/Built-in/standard Functions ===

A function is a block of statement is a block of that performs a specific task or return single/multiple new/modified

values of a function is as follows:

values to out side. The structure of a function is given below:

function_return_type fun_name ([parameter list]){

fun_body;

}

Every function must have a useful name.

The parameter list is optional but a pair of parenthesis is must which differentiate

the function name from the variable/named constant.The use of parameters is to

receive/supply value(s) from/to outside.

Function return type may be void (means returns nothing using return st),constant name

or any standard data type(may be int, long, unsigned int/long, char or unsigned char,

float, double, long double), which is the type of the value that the

function returns using return statement.

The body contains single/multiple st(s) under a pair of block markers.

Functions are of two types:

a) built-in/standard/simple type

b) user defined type.

We will study in this class the built-in functions of different classes/categories.

All the built-in types are called value return function that means they return a value

to the calling statement using return statement. This type of function is treated as

a value.You must call/use them as an operand of an other statement/expression.

**=== Algebric functions===**

#include <stdio.h>

#include <conio.h>

#include <math.h>//for math functions

void pause(){printf(“\nPress any key to continue..”); getch();}

void ex1(){

/*abs(n) absolute function that returns the absolute value of x, where

x in an int value.

fabs(x)where x is float value */

printf(“\nThe absolute value of an int value -3 is %d”,abs(-3)); //could be a int var/expr

pause();float b=-12.45;

printf(“\nThe value b is %.2f”,b);

printf(“\nThe absolute value of float var b is %.2f”,fabs(b));//error

/*sqrt(x) returns the square root of x, x can never be negative*/

//printf(“\nsquare root of b is %.2f”,sqrt(b));//b can’t be -ve, gives garbage value

printf(“\ncorrect sqrt(b) should be sqrt(fabs(b)) is %.2f”,sqrt(fabs(b)));

/*exp(x) returns the value of e to the power x*/

printf(“\ne to the power 1.0 is %.2f”,exp(1.0));//2.72, do the same for b

/*log(x): Its a natural log*/

printf(“\nlog(10.0) is %.2f”,log(10.0));//ans is 2.30

/*log10(x) : it is ten base log*/

printf(“\nlog10(10.0) is %.2f”,log10(10.0));//ans is 1

/*NOTE: log(n)=2.30*log10(n)==*/

//==floor(x): x rounded down to the nearest integer

float f=2.34;printf(“\nfloor(2.54) is %.f)”, floor(2.54));//2

//==cell(x) x rounded up to the nearest integer

printf(“\nceil(2.53) is %f”,ceil(2.53)); //3

//==pow(x,n) returns the x to the power n

f=pow(2,2.34); printf(“\n2 to the power 2.54 is %f”, pow(2,2.54));

//arguments of pow() are float/double/int

**/*==character functions===*/**

void ex2(){

/*getch(), getche() returns a character from the keyboard. They don’t need

to press ENTER key while supplying the value from the keyboard. Thery are

call unbuffered function. */

printf(“\nPress any key to continue pl…”);

getch(); //waits to press a character. The character will not echo on the screen.

printf(“\nPress another key to continue pl…”);

getche(); //will the character you press in the keyboard

//In the above we did not preserve/store any where the value you pressed.

//U can use these two functions using another way..

printf(“\nPress a key third times to continue pl…”);

char ch=getch(); printf(“\nThe character u pressed is %c”,ch);

/*getcha(ch) read a character from the keyboard, need to press ENTER after

pressing the character. putchar(ch) display/put the character on the screen. */

printf(“\nGive me a character pl”);

char ch1=getchar(); printf(“\nThe given character is: “);putchar(ch1);

}

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