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

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Question 141

C & C Plus Plus
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Describe in Detail

Essay▾

What is the problem with the following code segment?

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

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

C & C Plus Plus
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Describe in Detail

Essay▾

Find the output for the following C program

  1. #defineswap1 (a, b)a =a +b; b =a-b; a =a-b;
  2. voidmain ()
  3. {
  4.     intx =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. intswap2 (inta, intb)
  11. {
  12.     inttemp;
  13.     temp =a;
  14.     a=b;
  15.     b =temp;
  16.     return;
  17. }

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. intswap2 (inta, intb)
  2. {
  3.     inttemp;
  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

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