While Loop in C

This is a discussion on While Loop in C within the C Programming forums, part of the General Programming Boards category; Hi, I am trying to create a log table to use with a uC. My program is below. It works ...

  1. #1
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    Apr 2008
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    3

    While Loop in C

    Hi,

    I am trying to create a log table to use with a uC.
    My program is below. It works for tables up to about 300 lines.
    If I increase it, I lose the top lines in the table in the CMD window
    How can I make it so it will do 4096 lines.
    Also what would be the best way to output it in a .txt file?

    Thanks

    Code:
    #include <math.h>
    #include <stdio.h>
    
    int main( void )
    {
    
    int i=1;
    double x = 1.0, y = 1.0067, z;
    
    z= (x*y);
    printf("%d  %1f  \n",i,x);
    i++;
    while (i<=100) {
    printf("%d  %1f  \n",i,z);
    
    z= (z*y);
     i++;}
    
    
      return 0;
    }

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    14,185
    If you want 4096 lines in your command prompt window, you'll have to fiddle with your command prompt. To get a file, you need to look at fopen and fprintf.

  3. #3
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    Output to .txt

    Thanks for the tip on the CMD window. That is much better now.

    I have looked at the fopen and tried a few things but I am having trouble incorporating
    into the loop. All I can get it to do is print the last line to a file.

    Any code examples would be helpful. I am a real beginner and am not
    getting it.

    Thanks

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Nov 2007
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    14,185
    You shouldn't keep opening/closing the file inside the loop -- open it before the loop starts, then each pass through the loop should just add one line.

  5. #5
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    I got it now thanks

    Here is how I did it.



    Code:
    #include <math.h>
    #include <stdio.h>
    
    int main( void )
    {
    
      int i=1;
      double x = 1.0, y = 1.0020, z;
    
      FILE *fp;
    fp=fopen("test.txt", "w");
    
    
    z= (x*y);
        printf("%d  %1f \n",i,x);
    	fprintf(fp,"%d  %1f \n",i,x);
    	i++;
      while (i<=4096) {
    	  	    printf("%d  %1f\n",i,z);
    				  	    fprintf(fp,"%d  %1f\n",i,z);
    
    z= (z*y);
     i++;}
     
      return 0;
    }

  6. #6
    Registered User
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    Apr 2008
    Posts
    2
    Make sure you call:
    Code:
    fclose(fp);
    before your program ends. You should put that before the return.

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