how to end the cycle

[dragon fishy]

1 #include <stdio.h>
  2         
  3 void main() 
  4         
  5 {       
  6     unsigned int i;
  7     int c;
  8           
  9     printf("\nThis is a test start...\n");
 10 
 11     c=getchar();
 12     while(c!=EOF){
 13         putchar(c);
 14         c=getchar();
 15     }
 16 
 17 
 18 
 19     printf("This is the end of the test. \n");
 20 
 21 }

what should i input to end the cycle?
please help ,thanks.

[Banfa]

You will never get EOF from stdin because all the input functions wait for input if there is current none in the buffer. The stream never ends, or more accurately only ends when the program closes.

However you have not given an accurate enough (or any in fact) description of what "the cycle" is or what your program is meant to do. You should halt the look when the program is completed its purpose is the best I can say from the available information.

[dragon fishy]

Thanks a lot .You answer is good enough to help me out,and I appriciate your patience and kindness to make such an precise description.I wish you can understand my meaning,because I am a Chinese boy for whom Enlish is not that easy.Thank you again.

[Banfa]

OK well this is a simple program, it looks like to are just playing around while learning which is fair enough.

What your program basically does is read a character from the keyboard and write that character to the screen, repeatedly. You need to understand how the input stream works a little. Data does not (normally) enter the input stream as soon as the user presses a key but rather all the data the user has entered, including the new line, is put on the input stream when the user presses "Enter".

So how are you expecting the user to enter data? Are you expecting them to enter a few characters and press enter repeatedly, for example as if entering a list of numbers

4
356
34
64

Or are you expecting the user user to just enter a line of text with only a single press of "Enter"?

These are 2 distinct cases (and there are others) and require different handling. The second case is the simplest, the user is expected to enter a single line of data followed by "Enter". The defining feature of this is that "Enter" is pressed once so you can look for that in you input stream. Your loop condition can be c != '\n' i.e. as long as the character end is not the newline character, generated by the "Enter" key, then continue.

On the other hand the first example, entering a list of numbers is more complex. There is no defining feature, there is nothing that occurs only once at the end of the list. The normal way to get round this is to use a sentinel character, that is a character that is defined for the specific purposes of the program as indicating the end. In the case entering a list of numbers you could use the character q, the program will except a list on numbers up until it reads the character q and then it will quit. The input would look something like

4
356
34
64
q

and the loop condition might look something like c != 'q'.

[dragon fishy]

Ok.I can undertand what you said and I know the method can totally fix the problem of endless cycle.The program is from the book 《The C Progamming Language》,and I just test it and that is all.

I supposed there is a charater I can input to end the loop( Of cause I konw this can not happen now) because I thought there can be a character equal 'EOF' (ie -1). According to what you said ,now I know stdio can not do that.I will study further into the input stream staff.Thanks for explaining for me.

O(∩_∩)O~

Tell you a joke,I even input '-1' to expect the loop to come to an end...

wish you a good night.

sorry ,I should say wish you a good say.because the time zone is diffrent
-_-|||