C file function questions

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I am taking a C++ class this semester. It is right now covering C material*and will switch to C++ material mid-semester. Anyway, in the textbook, there is the following code:

 

#include

 

int main(void)

{

 

int a, sum = 0;

FILE *ifp, *ofp;

 

ifp = fopen("my_file", "r");

ofp = fopen("outfile", "w");

...

 

The textbook then explains*the above code, saying that*it opens*two files in the current*directory. Is the current directory by default*the directory of the executable or the root directory?

 

It then proceeds to say that if my_file contains integers, we want to sum them and put the result in outfile, we can write:

 

while(fscanf(ifp, "%d", &a) == 1)

*** sum += a;

fprintf(ofp, "The sum is %d.\n", sum);

 

Since this is in the textbook, I would expect it to sum all of the values and print the growing sum as the summation occurs, but it looks like an infinite loop to me.*I can see how it could end, being that the pointer reaches the end of file, but I do not see how it increments itself. Does this code even work and if it does, how does it work?

 

After this it calls fclose().

 

 

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