C Program to determine a file’s attributes.

How to determine a file’s attributes?

The file attributes are stored in the find_t.attrib structure member. This structure member is a single character, and each file attribute is represented by a single bit. Here is a list of the valid DOS file attributes:

C Program to sort filenames in a directory?

How do you sort filenames in a directory?

The below example shows how to get a list of files one at a time. The example uses the _dos_findfirst() and _dos_findnext() functions to walk through the directory structure. As each filename is found, it is printed to the screen.

When you are sorting the filenames in a directory, the one-at- a-time approach does not work. You need some way to store the filenames and then sort them when all filenames have been

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 15

Predict the output or error(s) for the following:

1)

main()

{

int i=_l_abc(10);

printf("%d\n",--i);

}

int _l_abc(int i)

{

 return(i++);

}

Answer:

9

Explanation:

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 14

Predict the output or error(s) for the following:

1)

struct point

{

 int x;

 int y;

 };

struct point origin,*pp;

main()

{

pp=&origin;

printf("origin is(%d%d)\n",(*pp).x,(*pp).y);

printf("origin is (%d%d)\n",pp->x,pp->y);

}

Answer:

origin is(0,0)

origin is(0,0)

Explanation:

How do you list a file’s date and time?

A file’s date and time are stored in the find_t structure returned from the _dos_findfirst() and _dos_findnext() functions.

The date and time stamp of the file is stored in the find_t.wr_date and find_t.wr_time structure members. The file date is stored in a two-byte unsigned integer as shown here:

Because DOS stores a file’s seconds in two-second intervals, only the

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 13

Predict the output or error(s) for the following:

1)

#include<stdio.h>

main()

{

  int a[2][2][2] = { {10,2,3,4}, {5,6,7,8}  };

  int *p,*q;

  p=&a[2][2][2];

  *q=***a;

  printf("%d..%d",*p,*q);

}

Answer:

garbagevalue..1

Explanation:

How do you list files in a directory?

Unfortunately, there is no built-in function provided in the C language such as dir_list() that would easily provide you with a list of all files in a particular directory. By utilizing some of C’s built-in directory functions, however, you can write your own dir_list() function.

First of all, the include file dos.h defines a structure named find_t, which represents the structure of the DOS file entry block. This

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 12

Predict the output or error(s) for the following:

1)

int i=10;

main()

{

extern int i;

{

int i=20;

{

const volatile unsigned i=30;

printf("%d",i);

}

printf("%d",i);

}

printf("%d",i);

}

Answer:

30,20,10

Explanation:

What is the difference between text and binary modes?

Streams can be classified into two types: text streams and binary streams. Text streams are interpreted, with a maximum length of 255 characters. With text streams, carriage return/line feed combinations are translated to the newline \n character and vice versa. Binary streams are uninterpreted and are treated one byte at a time with no translation of characters. Typically, a text stream would be used for reading and writing standard text files, printing

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 11

Predict the output or error(s) for the following:

1)

main()

{

int k=1;

printf("%d==1 is ""%s",k,k==1?"TRUE":"FALSE");

}

Answer:

1==1 is TRUE

Explanation:

How can you restore a redirected standard stream?

The preceding example showed how you can redirect a standard stream from within your program. But what if later in your program you wanted to restore the standard stream to its original state? By using the standard C library functions named dup() and fdopen(), you can restore a standard stream such as stdout to its original state.

The dup() function duplicates a file handle. You can use the dup() function to save the file handle corresponding to the stdout standard

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 10

Predict the output or error(s) for the following:

1)

main()

{

char *str1="abcd";

char str2[]="abcd";

printf("%d %d %d",sizeof(str1),sizeof(str2),sizeof("abcd"));

}

Answer:

2 5 5

Explanation:

If errno contains a nonzero number, is there an error?

The global variable errno is used by many standard C library functions to pass back to your program an error code that denotes specifically which error occurred. However, your program should not check the value of errno to determine whether an error occurred.

Usually, the standard C library function you are calling returns with a return code which denotes that an error has occurred and that the

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 9

Predict the output or error(s) for the following:

1)

main()

{

char *cptr,c;

void *vptr,v;

c=10;  v=0;

cptr=&c; vptr=&v;

printf("%c%v",c,v);

}

Answer:

Compiler error (at line number 4): size of v is Unknown.

Explanation:

What is hashing?

To hash means to grind up, and that’s essentially what hashing is all about. The heart of a hashing algorithm is a hash function that takes your nice, neat data and grinds it into some random-looking integer.

The idea behind hashing is that some data either has no inherent ordering (such as images) or is expensive to compare (such as images). If the data has no inherent ordering, you can’t perform comparison searches. If the data is expensive to compare, the

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 8

Predict the output or error(s) for the following:

1)

int i,j;

for(i=0;i<=10;i++)

{

j+=5;

assert(i<5);

}

Answer:

Runtime error: Abnormal program termination.

assert failed (i<5), <file name>,<line number>

Explanation:

What is the quickest searching method to use?

A binary search, such as bsearch() performs, is much faster than a linear search. A hashing algorithm can provide even faster searching. One particularly interesting and fast method for searching is to keep the data in a “digital trie.” A digital trie offers the prospect of being able to search for an item in essentially a constant amount of time, independent of how many items are in the data set.

A digital trie combines aspects of binary searching, radix searching, and hashing. The term “digital trie” refers to the data structure used to hold the items to be searched. It is a multilevel data structure that

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 7

Predict the output or error(s) for the following:

1)

main ( )

{

 static char *s[ ]  = {“black”, “white”, “yellow”, “violet”};

 char **ptr[ ] = {s+3, s+2, s+1, s}, ***p;

 p = ptr;

 **++p;

 printf(“%s”,*--*++p + 3);

}

Answer:

ck

Explanation:

What is the easiest searching method to use?

Just as qsort() was the easiest sorting method, because it is part of the standard library, bsearch() is the easiest searching method to use.

Following is the prototype for bsearch():

void *bsearch(const void *key, const void *buf, size_t num, size_t size, int (*comp)(const void *, const void *));

The bsearch() function performs a binary search on an array of sorted data elements. A binary search is another “divide and conquer” algorithm. The key is compared with the middle element of

Frequently Asked Questions in Technical Round at MNCs like TCS, WIPRO, INFOSYS,..etc – 6

Predict the output or error(s) for the following:

1)

main( )

{

 void *vp;

 char ch = ‘g’, *cp = “goofy”;

 int j = 20;

 vp = &ch;

 printf(“%c”, *(char *)vp);

 vp = &j;

 printf(“%d”,*(int *)vp);

 vp = cp;

 printf(“%s”,(char *)vp + 3);

}

Answer:

g20fy

Explanation: