Data Transfer Question

[maiios]

I was writing a program that had a whole bunch of data transfer, when I realized that I have almost no idea what goes on behind the scenes of such an endevor. I am not the type of person who likes to have things happen "magically" so I was wondering if anyone knew how it worked. I have already scoured the web but have not found much of anything on this topic. But here is what I am talking about.

For example;

#include <stdio.h>
main &#40;&#41;
&#123;
   char c ;
   FILE *fp;
   if &#40;&#40; fp = fopen &#40;"output.txt", "w"&#41;&#41; == NULL &#41;
      printf &#40;"\n Cannot open the file&#58; output.txt\n"&#41;;
   else
      &#123;
         c = 'a';
         fputc &#40; c, fp&#41;;
         fclose &#40;fp&#41;;
      &#125;
&#125;

When this program begins to execute, the character 'a' will be placed in memory by the C run-time environment. This character will then be sent to a file "output.txt".

I want to know how 'a' is bound to a particular place in memory. I also want to know what happens to get this character to a particular physical record on a physical disk unit.

I know this is kind of an advanced question, but I would love it if someone knew the answer, or if someone could point me in the right direction (because my searches didn't bring up anything close to what I wanted).

[lakerdonald]

#include <stdio.h>
main &#40;&#41;
&#123;
   char c ;
   FILE *fp;
   if &#40;&#40; fp = fopen &#40;"output.txt", "w"&#41;&#41; == NULL &#41;
      printf &#40;"\n Cannot open the file&#58; output.txt\n"&#41;;
   else
      &#123;
         c = 'a';
         fputc &#40; c, fp&#41;;
         fclose &#40;fp&#41;;
      &#125;
&#125;

1. 1 byte of memory is automagically allocated. It can hold one character ( integers -127 through 127 ) and is referenced by the label c
2. A pointer to a FILE structure is created, and given the name 'fp'
3. Several things happen:
First, output.txt is open()'d. If doesn't exist, it is created. If it already exists, then it is next truncated.
Then, fp is set to point to that memory
4. c now contains the integer 0x61 ( decimal 97, which is the ASCII code for the letter 'a' )
5. c, which contains the integer 0x61 ( decimal 97, ASCII a ), is copied to the file stream ( output.txt ) pointed to by the FILE pointer fp
6. The FILE descriptor fp is closed
-lakerdonald