Get the mantissa and exponent form of a given number

37. Allocating memory for a 3-D array

#include "alloc.h"

#define MAXX 3

#define MAXY 4

#define MAXZ 5

main( )

{

int ***p, i, j, k ;

p = ( int *** ) malloc ( MAXX * sizeof ( int ** ) ) ;

for ( i = 0 ; i <>

{

p[i] = ( int ** ) malloc ( MAXY * sizeof ( int * ) ) ;

for ( j = 0 ; j <>

p[i][j] = ( int * ) malloc ( MAXZ * sizeof ( int ) ) ;

}

for ( k = 0 ; k <>

{

for ( i = 0 ; i <>

{

for ( j = 0 ; j <>

{

p[i][j][k] = i + j + k ;

printf ( "%d ", p[i][j][k] ) ;

}

printf ( "\n" ) ;

}

printf ( "\n\n" ) ;

}

}

Data Structures

How to distinguish between a binary tree and a tree?

Ans: A node in a tree can have any number of branches. While a binary tree is a tree structure in which any node can have at most two branches. For binary trees we distinguish between the subtree on the left and subtree on the right, whereas for trees the order of the subtrees is irrelevant.

Consider the following figure...

This above figure shows two binary trees, but these binary trees are different. The first has an empty right subtree while the second has an empty left subtree. If the above are regarded as trees (not the binary trees), then they are same despite the fact that they are drawn differently. Also, an empty binary tree can exist, but there is no tree having zero nodes.

38. How do I use the function ldexp( ) in a program?

Ans: The math function ldexp( ) is used while solving the complex mathematical equations. This function takes two arguments, a double value and an int respectively. The order in which ldexp( ) function performs calculations is ( n * pow ( 2, exp ) ) where n is the double value and exp is the integer. The following program demonstrates the use of this function.

#include 

#include 

void main( )

{

double ans ;

double n = 4 ;

ans = ldexp ( n, 2 ) ;

printf ( "\nThe ldexp value is : %lf\n", ans ) ;

}

Here, ldexp( ) function would get expanded as ( 4 * 2 * 2 ), and the output would be the ldexp value is : 16.000000

39. Can we get the mantissa and exponent form of a given number?

Ans: The function frexp( ) splits the given number into a mantissa and exponent form. The function takes two arguments, the number to be converted as a double value and an int to store the exponent form. The function returns the mantissa part as a double value. Following example demonstrates the use of this function.

#include 

#include 

void main( )

{

double mantissa, number ;

int exponent ;

number = 8.0 ;

mantissa = frexp ( number, &exponent ) ;

printf ( "The number %lf is ", number ) ;

printf ( "%lf times two to the ", mantissa ) ;

printf ( "power of %d\n", exponent ) ;

return 0 ;

}

40. How do I write code that executes certain function only at program termination?

Ans: Use atexit( ) function as shown in following program.

#include 

main( )

{

int ch ;

void fun ( void ) ;

atexit ( fun ) ;

// code

}

void fun( void )

{

printf ( "\nTerminate program......" ) ;

getch( ) ;

}

43. If the result of an _expression has to be stored to one of two variables, depending on a condition, can we use conditional operators as shown below?

( ( i <>

Ans: No! The above statement is invalid. We cannot use the conditional operators in this fashion. The conditional operators like most operators, yields a value, and we cannot assign the value of an _expression to a value. However, we can use conditional operators as shown in following code snippet.

main( )

{

int i, j, k, l ;

i = 5 ; j = 10 ; k = 12, l = 1 ;

* ( ( i <>

printf ( "i = %d j = %d k = %d l = %d", i, j, k, l ) ;

}

The output of the above program would be as given below:

i = 5 j = 16 k = 12 l = 1

44. How can I find the day of the week of a given date?

Ans: The following code snippet shows how to get the day of week from the given date.

dayofweek ( int yy, int mm, int dd )

{

/*Monday = 1 and Sunday = 0 */

/* month number >= 1 and <= 12, yy > 1752 or so */

static int arr[ ] = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 } ;

yy = yy - mm <>

return ( yy + yy / 4 - yy / 100 + yy / 400 + arr[ mm - 1] + dd ) % 7 ;

}

void main( )

{

printf ( "\n\n\nDay of week : %d ", dayofweek ( 2002, 5, 18 ) ) ;

}

45. What's the difference between these two declarations?

struct str1 { ... } ;

typedef struct { ... } str2 ;

Ans : The first form declares a structure tag whereas the second declares a typedef. The main difference is that the second declaration is of a slightly more abstract type -- its users don't necessarily know that it is a structure, and the keyword struct is not used when declaring instances of it.