fflush example in C

Header file:

     stdio.h

Synopsis:

     int fflush(FILE *stream);

     

Description:

     For output streams, fflush() makes any buffered unwritten data to be written.  And the behavior is undefined for input stream.  fflush(NULL) flushes all output streams.  Returns 0 on success.  Otherwise, EOF is returned.

fflush function C example:

  /* Please try this program in Turbo C to get the exact output */

 #include<stdio.h>

  #include<string.h>

  int main() {

        char ch1, ch2;

        printf("Enter your 1st character:\n");

        scanf("%c", &ch1);

        /* flushes standard i/p. So the \n will get flushed */

        fflush(stdin);

        printf("Enter your 2nd character:\n");

        scanf("%c", &ch2);

        printf("ch1:%c\tascii of ch1:%d\n", ch1, ch1);

        printf("ch2:%c\tascii of ch2:%d\n", ch2, ch2);

        return 0;

  }

  Output:

 jp@jp-VirtualBox:~/cpgms/exp$ ./a.out
  Enter your 1st character:
  a
  Enter your 2nd character:

  b
  ch1:a    ascii of ch1:97
  ch2:b    ascii of ch2:98

In the above program, fflush() flushes the input stream('\n' newline character is wiped off).


Lets rewrite the above program without fflush(stdin) and check the output.

  #include<stdio.h>

  #include<string.h>

  int main() {

        char ch1, ch2;

        printf("Enter your 1st character:\n");

        scanf("%c", &ch1);

        printf("Enter your 2nd character:\n");

        scanf("%c", &ch2);

        printf("ch1:%c\tascii of ch1:%d\n", ch1, ch1);

        printf("ch2:%c\tascii of ch2:%d\n", ch2, ch2);

        return 0;

  }

  Output:

  jp@jp-VirtualBox:~/cpgms/exp$ ./a.out

  Enter your 1st character:

  a

  Enter your 2nd character:

  ch1:a    ascii of ch1:97

  ch2:

    ascii of ch2:10

Here, ch2 takes '\n' as its input and the same is printed on the output screen.