tk1913-c programming1 tk1913-c programming 1 c library functions c provides a collection of library...

TK1913-C ProgrammingTK1913-C Programming 11

C Library FunctionsC Library Functions C provides a collection of library functions for

programmers

If these library functions are used in a program,

be sure to include their prototypes. Library

function prototypes are placed in specific header

files.

Example: Function prototypes of printf() and

scanf() can be found in header file stdio.h.


To include a function prototype defined in a

header file into our program, use the

preprocessor instruction #include.

Example,

#include <stdio.h>

#include <math.h>


math math Library functionLibrary function One type of library functions which

provides several functions for execution of mathematic operations is math

Prototypes of these functions are declared in a header file named math.h


Example: sqrt() function This function can be used to attain the square root of a given number The function declaration:

Example:double num; printf(“Input a number: ");scanf("%lf", &num);printf(“Square root of %.2lf: %.2lf\n”, num, sqrt(num));

double sqrt(double n);

The number its square root you

want to get

The data type returned by

function sqrt()

math math Library functionLibrary function


Example: abs() function This function is used to get the absolute value of a

number The function declaration:

Example:int num, abs_value; printf(“Input number: ");scanf("%d", &num);abs_value = abs(num);printf(“Absolute value for %d: %d\n”, num, abs_value);

int abs(int n);

The number its absolute value you want to get

The data type returned by abs()

function

math math Library functionLibrary function


Variable scopeVariable scope There are two types of scope for variables: local

and global Local variable :

May only be accessed and manipulated in the block where it is declared

Global variable : May be accessed and manipulated anywhere in a

program, including in user-defined functions Must be declared outside a function definition Is not encouraged because program readability may

be compromised and maintenance more tedious


#include <stdio.h>

void negative(int);int main( ) {

int num;scanf("%d", &num);negative(num);printf(“Value of num is now: %d\n", num);

}void negative(int number) {

number = -number;}

Example:

???

num

???

number

Variable scope : local variablesVariable scope : local variables


In the following example, the variable number in main() and variable number in negative() are not referring to the same memory location. Both are local variable

Variable scope : local variablesVariable scope : local variables

number

#include <stdio.h>void negative(int);int main( ) {

int number;scanf("%d", &number);negative(number);printf(“Value of number is now: %d\n", number);

}void negative(int number) {

number = - number;}

void negative(int number)number

int main( )


In the following example, number in main() and negative() are referring to the same memory location #include <stdio.h>void negative();int number;int main( ) {

scanf("%d", &number);negative();printf(“Value of number is now : %d\n", number);

}void negative() {

number = -number;}

Variable scope : global variablesVariable scope : global variables

numberint main( )

void negative()


Can a function call itself ?

A function that calls itself is known as recursive

function

Recursive function is used to handle problem that

can be broken into sub-problem which resembles

the original problem, repeatedly until the solution

is achieved

Recursive FunctionRecursive Function


Example : Factorial formula can be written as :

1, when n = 0

n! =

n * (n-1) * … * 2 * 1 , when n

>= 1

In other words,

1, when n = 0

n! =

n * (n-1)! , when n >= 1

Recursive FunctionRecursive Function


factorial(5) = 5 * factorial(4)

Getting the value of factorial(5) using recursion

Recursive Function Example : factorialRecursive Function Example : factorial




















factorial(0) = 1





factorial(1) = 1 * 1

factorial(0) = 1





factorial(1) = 1





factorial(1) = 1




factorial(2) = 2




factorial(2) = 2



factorial(3) = 6



factorial(3) = 6


factorial(4) = 24


factorial(4) = 24

factorial(5) = 120


#include <stdio.h>int factorial(int n);int main() {

int n;printf(“Input n : ");scanf("%d", &n);printf(“Value of %d! = %d\n", n, factorial(n));

}int factorial( int n ) {

if (n == 0)return 1;

elsereturn (n * factorial(n - 1));

}

This is a recursive function becausea function call in its body calls itself.

factorial function (using recursion)factorial function (using recursion)




}int factorial( int n ) {



}

0! = 1

n! = n * (n – 1)!

factorial function (using recursion)factorial function (using recursion)




}int factorial(int n ) {



}

???

n

_

int main()

Input n :_

5

Input n : 5

5n1

Caller Called P/m passed Returned value

main fac-1 5

fac-1







}

5

n

Input n : 5

5n1int factorial(int n) {


main fac-1 5


main fac-1 5 5 * factorial(4)

fac-2 (4)

n2 4



fac-1 fac-2 4







}

5

n

Input n : 5


fac-3 (3)

n2 4



fac-1 fac-2 4



fac-1 fac-2 4 4 * factorial(3)

3n3




fac-2 fac-3 3







}

5

n

Input n : 5


fac-4 (2)

n2 4

3n3




fac-2 fac-3 3





n4 2





fac-3 fac-4 2







}

5

n

Input n : 5


fac-5 (1)

n2 4

3n3

n4 2





fac-3 fac-4 2






n5 1






fac-4 fac-5 1







}

5

n

Input n : 5

5n1

int factorial(int n) {

fac-6 (0)

n2 4

3n3

n4 2

n5 1






fac-4 fac-5 1







n6 0







fac-5 fac-6 0

1







fac-5 fac-6 0 1







}

5

n

Input n : 5

5n1

int factorial(int n) { n2 4

3n3

n4 2

n5 1






fac-4 fac-5 1 1 * 1

1






fac-4 fac-5 1 1







}

5

n

Input n : 5

5n1


3n3

n4 22





fac-3 fac-4 2 2 * 1





fac-3 fac-4 2 2




fac-2 fac-3 3 3 * 2







}

5

n

Input n : 5

5n1


3n36




fac-2 fac-3 3 3 * 2




fac-2 fac-3 3 6







}

5

n

Input n : 5

5n1


24



fac-1 fac-2 4 4 * 6



fac-1 fac-2 4 24







}

5

n

Input n : 5

5n1

int factorial(int n) {

120


main fac-1 5 5 * 24


main fac-1 5 120

Input n : 5

Value of 5! = 120

int main()






elsereturn (n * factorial(n -1));

}

Input n : 5

Value of 5! = 120

tk1913-c programming1 tk1913-c programming 1 c library functions c provides a collection of library...

Documents

variable number

given number

int number scanf

number variable scope

c library functions

local variables number

value printfinput number

int num scanf