Answer: /* Use printf () to print the first 11 characters of source_str. */
printf (“First 11 characters: ‘%11.11s’n”, source_str);
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printf() Function What is the output of printf("%d")? 1. When we write printf("%d",x); this means compiler will print the value of x. But as here, there is nothing after %d so compiler will show in output window garbage value. 2. When we use %d the compiler internally uses it to access the argument in the stack (argument stack). Ideally compiler determines the offset of the data variable depending on the format specification string. Now when we write printf("%d",a) then compiler first accesses the top most element in the argument stack of the printf which is %d and depending on the format string it calculated to offset to the actual data variable in the memory which is to be printed. Now when only %d will be present in the printf then compiler will calculate the correct offset (which will be the offset to access the integer variable) but as the actual data object is to be printed is not present at that memory location so it will print what ever will be the contents of that memory location. 3. Some compilers check the format string and will generate an error without the proper number and type of arguments for things like printf(...) and scanf(...).
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C interview question1:If we have declared an array as global in one file and we are using it in another file then why doesn't the sizeof operator works on an extern array?
Answer: An extern array is of incomplete type as it does not contain the size. Hence we cannot use sizeof operator, as it cannot get the size of the array declared in another file. To resolve this use any of one the following two solutions:
1. In the same file declare one more variable that holds the size of array. For example,
array.c
int arr[5] ;
int arrsz = sizeof ( arr ) ;
myprog.c
extern int arr[] ;
extern int arrsz ;
2. Define a macro which can be used in an array
declaration. For example,
myheader.h
#define SZ 5
array.c
#include "myheader.h"
int arr[SZ] ;
myprog.c
#include "myheader.h"
extern int arr[SZ] ;
C interview question2:How do I write printf( ) so that the width of a field can be specified at runtime?
Answer: This is shown in following code snippet.
main( )
{
int w, no ;
printf ( "Enter number and the width for the
number field:" ) ;
scanf ( "%d%d", &no, &w ) ;
printf ( "%*d", w, no ) ;
}
Here, an '*' in the format specifier in printf( ) indicates that an int value from the argument list should be used for the field width.
C interview question3:How to find the row and column dimension of a given 2-D array?
Answer: Whenever we initialize a 2-D array at the same place where it has been declared, it is not necessary to mention the row dimension of an array. The row and column dimensions of such an array can be determined programmatically as shown in following program.
void main( )
{
int a[][3] = { 0, 1, 2,9,-6, 8,7, 5, 44,23, 11,15 } ;
int c = sizeof ( a[0] ) / sizeof ( int ) ;
int r = ( sizeof ( a ) / sizeof ( int ) ) / c ;
int i, j ;
printf ( "\nRow: %d\nCol: %d\n", r, c ) ;
for ( i = 0 ; i < r ; i++ )
{
for ( j = 0 ; j < c ; j++ )
printf ( "%d ", a[i][j] ) ;
printf ( "\n" ) ;
}
}
C interview quesion4:What is access( ) function...
Answer:The access( ) function checks for the existence of a file and also determines whether it can be read,written to or executed. This function takes two arguments the filename and an integer indicating the access mode. The values 6, 4, 2, and 1 checks for read/write, read, write and execute permission of a given file, whereas value 0 checks whether the file exists or not. Following program demonstrates how we can use access( ) function to check if a given file exists.
#include
main( )
{
char fname[67] ;
printf ( "\nEnter name of file to open" ) ;
gets ( fname ) ;
if ( access ( fname, 0 ) != 0 )
{
printf ( "\nFile does not exist." ) ;
return ;
}
} C interview question5:How do I convert a floating-point number to a string?
Answer: Use function gcvt( ) to convert a floating-point number to a string. Following program demonstrates the use of this function.
#include
main( )
{
char str[25] ;
float no ;
int dg = 5 ; /* significant digits */
no = 14.3216 ;
gcvt ( no, dg, str ) ;
printf ( "String: %s\n", str ) ;
}
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