Delete a line from text displayed on the screen

64.How do I get the time elapsed between two function calls ?

Ans: The function difftime( ) finds the difference between two times. It calculates the elapsed time in seconds and returns the difference between two times as a double value.

#include 

#include 

#include 

main( )

{

int a[] = { 2, -34, 56, 78, 112, 33, -7, 11, 45, 29, 6 } ;

int s ;

time_t t1, t2 ; // time_t defines the value used for time function

s = sizeof ( a ) / 2 ;

t1 = time ( NULL ) ;

sel_sort ( a, s ) ; // sort array by selection sort

bub_sort ( a, s ) ; // sort array by bubble sort method

t2 = time ( NULL ) ;

printf ( "\nThe difference between two function calls is %f", difftime (

t2, t1 ) ) ;

}

In the above program we have called difftime( ) function that returns the time elapsed from t1 to t2. 

65. How do I use swab( ) in my program ?

Ans: The function swab( ) swaps the adjacent bytes of memory. It copies the bytes from source string to the target string, provided that the number of characters in the source string is even. While copying, it swaps the bytes which are then assigned to the target string.

#include 

#include 

#include 

main ( )

{

char *str1 = "hS eesll snsiasl not eh es as oher " ;

char *str2 ;

clrscr( ) ;

swab ( str1, str2, strlen ( str1 ) ) ;

printf ( "The target string is : %s\n", str2 ) ; // output -- She sells

snails on the sea shore

getch( ) ;

}

66. Turbo C provides various command line compiler options which we can use through TCC. The compiler options include : displaying specific warning messages, generating 8087 hardware instructions, using a filename for generating assembly code, etc. Instead of compiler options being executed at command line we can use these compiler options in our program. This can be achieved using #pragma options. We can use various flags with #pragma options to use the compiler options. All these flags are available in turbo C's online help.

67. I have an array declared in file 'F1.C' as,

int a[ ] = { 1, 2, 3, 4, 5, 6 } ;

and used in the file 'F2.C' as,

extern int a[ ] ;

In the file F2.C, why sizeof doesn't work on the array a[ ]?

Ans: An extern array of unspecified size is an incomplete type. You cannot apply sizeof to it, because sizeof operates during compile time and it is unable to learn the size of an array that is defined in another file. You have three ways to resolve this problem:

1. In file 'F1.C' define as,

int a[ ] = { 1, 2, 3, 4, 5, 6 } ;

int size_a = sizeof ( a ) ;

and in file F2.C declare as,

extern int a[ ] ;

extern int size_a ;

2. In file 'F1.H' define,

#define ARR_SIZ 6

In file F1.C declare as,

#include "F1.H"

int a[ ARR_SIZ ] ;

and in file F2.C declare as,

#include "F1.H"

extern int a[ ARR_SIZ ] ;

3. In file 'F1.C' define as,

int a[ ] = { 1, 2, 3, 4, 5, 6, -1 } ;

and in file 'F2.C' declare as,

extern int a[ ] ;

Here the element -1 is used as a sentinel value, so the code can

understand the end without any explicit size.

68. How to delete a line from text displayed on the screen?

Ans: Sometimes, specially when we are creating a text editor like program we may wish to allow user to delete a line. We can do so by using two functions namely clreol( ) and delline( ). The clreol( ) function deletes the line from the current cursor position to the end of line. The delline() function deletes the entire line at the current cursor position and

moves up the following line. Following program shows how to use these functions.

#include 

main( )

{

int i ;

for ( i = 1 ; i <= 20 ; i++ )

printf ( "This is Line %d\n", i ) ;

getch( ) ;

gotoxy ( 1, 7 ) ;

clreol( ) ;

getch( ) ;

gotoxy ( 1, 12 ) ;

delline( ) ;

getch( ) ;

}

69. How do I programmatically insert lines in the text window?

Ans: We can insert a blank line in the text window using the insline( ) function. This function inserts line at current cursor position. While doing so, it shifts down the lines that are below the newly inserted line.

#include 

void main( )

{

printf ( "The little snail was slowly moving up. She wanted\r\n" ) ;

printf ( "to reach the top of the tree. It was chilly\r\n" ) ;

printf ( "winter season. Most of the animals were resting in\r\n" ) ;

printf ( "their nests as there was a heavy snow fall.\r\n" ) ;

printf ( "\r\nPress any key to continue:" ) ;

gotoxy ( 10, 2 ) ;

getch( ) ;

insline( ) ;

getch( ) ;

}

70. What will be the output of the following program?

main( )

{

unsigned int num ;

int i ;

printf ( "\nEnter any number" ) ;

scanf ( "%u", &num ) ;

for ( i = 0 ; i <>

printf ( "%d", ( num <<>

}

Ans: The output of this program is the binary equivalent of the given number. We have used bitwise operators to get the binary number.