Languages-C & C Plus Plus [3i Infotech Placement]: Sample Questions 141 - 142 of 354

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Question 141

Describe in Detail Essay▾

What is the problem with the following code segment?

While ( (fgets (receiving array, 50, file_ptr) ) ! = EOF) ;

Edit

Explanation

  • fgets returns a string pointer not file pointer (string pointer can be NULL not EOF) . So the correct end of file check is checking for! = NULL.
  • Function char ⚹ fgets (char ⚹ str, int n, FILE ⚹ stream) reads a line from the specified stream and stores it into the string pointed to by str.
  • It stops when (n-1) characters are read, the newline character is read, or the end-of-file is reached, whichever comes first.

Example:

Example Shows the Usage of Fgets () Function
  • Let us assume, we have a text file file. txt, which has the following content. This file will be used as an input for our example program:

    “We are in 2017”

  • Now, let us compile and run the above program that will produce the following result:

We are in 2017

Question 142

Describe in Detail Essay▾

Find the output for the following C program

  1. #define swap1 (a, b)a =a +b; b =a-b; a =a-b;
  2. void main ()
  3. {
  4. int x =5, y =10;
  5. swap1 (x, y);
  6. printf ( “%d %d”, x, y);
  7. swap2 (x, y);
  8. printf ( “%d %d” ,x, y);
  9. }
  10. int swap2 (int a, int b)
  11. {
  12. int temp;
  13. temp =a;
  14. a=b;
  15. b =temp;
  16. return;
  17. }
Edit

Explanation

  • In the program
Table Showing the Program
#define swap1 (a, b) a = a + b; b = a-b; a = a-b;
  • define the swap1 () function using preprocessor directive- swap the value of x and y
  1. int swap2 (int a, int b)
  2. {
  3. int temp;
  4. temp =a;
  5. b =a;
  6. b =temp;
  7. return;
  8. }
  • define the swap2 () function using actual function- swaps the values
  • define the integer variable temp
  • Temp variable stores the value of a
  • b stored in the a
  • b stored in temp
int x = 5, y = 10;
  • define the integer variable x = 5 and y = 10
swap1 (x, y) ;
  • Apply the swap1 () function
printf ( “% d % d” , x, y) ;
  • printf prints the value of x and y swapped by swap1 () function
swap2 (x, y) ;
  • Apply the swap2 () function
printf ( “% d % d” , x, y) ;
  • swap2 changes the value inside the function but does not change it outside