struct elements erasing itself - c

Question

Ok so I am reading some things from files with this code:
for (i=0; i<start;i++)
{
filename=files[i];
if((fp=fopen(filename, "r"))==NULL)
{
printf("unable to open %s\n", filename);
exit(1);
}
while(fgets(buffer, sizeof(buffer), fp) !=NULL)
{
d[counter].id=atoi(strtok(buffer, del));
strcpy(buffer2, strtok(NULL, del));
len=strlen(buffer2);
if(buffer2[len-1]=='\n')
buffer2[len-1]='\0';
strcpy(d[counter].name, buffer2);
counter++;
}
token = strtok (filename, del1);
holder=token;
token = strtok (NULL, del1); /* section*/
token2 = strtok(holder, del2);
token2 = strtok(NULL, del2); /*course name */
for(x=z;x<counter;x++)
{
d[x].section=atoi(token);
printf("%d ", d[x].section);
strcpy(d[x].course, token2);
printf("%s %d %s %d\n", d[x].course, d[x].section, d[x].name, d[x].id);
}
z=counter;
}
Struct definition:
struct student {
char course[8];
int section;
char name[19];
int id;
};
Everything prints fine except for the "section" in the struct, for some reason the elements makes itself 0 after a certain amount.
Here is the output:
1 CSE1325 1 Sally 3233
1 CSE1325 1 George 9473
2 CSE1325 2 Tom 1234
2 CSE1325 2 Ralph 3540
2 CSE1325 2 Mary 5678
1 CSE2312 1 Tom 1234
1 CSE2312 1 Ralph 3540
1 CSE2312 1 Mary 5678
1 CSE2315 1 Tom 1234
1 CSE2315 1 Ralph 3540
1 CSE2315 1 Mary 5678
2 CSE2315 2 Sally 3233
2 CSE2315 2 George 9473
4 ENGL1301 0 Tom 1234
4 ENGL1301 0 Sally 3233
4 ENGL1301 0 Ralph 3540
4 ENGL1301 0 Mary 5678
4 ENGL1301 0 George 9473
1 HIST1311 0 Tom 1234
1 HIST1311 0 Sally 3233
1 HIST1311 0 Ralph 3540
1 HIST1311 0 Mary 5678
1 HIST1311 0 George 9473
5 MATH1426 0 Sally 3233
5 MATH1426 0 George 9473
This is the expected output:
1 CSE1325 1 Sally 3233
1 CSE1325 1 George 9473
2 CSE1325 2 Tom 1234
2 CSE1325 2 Ralph 3540
2 CSE1325 2 Mary 5678
1 CSE2312 1 Tom 1234
1 CSE2312 1 Ralph 3540
1 CSE2312 1 Mary 5678
1 CSE2315 1 Tom 1234
1 CSE2315 1 Ralph 3540
1 CSE2315 1 Mary 5678
2 CSE2315 2 Sally 3233
2 CSE2315 2 George 9473
4 ENGL1301 4 Tom 1234
4 ENGL1301 4 Sally 3233
4 ENGL1301 4 Ralph 3540
4 ENGL1301 4 Mary 5678
4 ENGL1301 4 George 9473
1 HIST1311 1 Tom 1234
1 HIST1311 1 Sally 3233
1 HIST1311 1 Ralph 3540
1 HIST1311 1 Mary 5678
1 HIST1311 1 George 9473
5 MATH1426 5 Sally 3233
5 MATH1426 5 George 9473
See how the numbers match? But for mine it doesn't, when I print d[x].section in the for loop as a standalone it prints the correct thing, but when I use it in that combined print statement for some reason it prints out 0 when reaching ENGL1301.

Answer 1

The course number can be eight characters, and strings in C are by convention null-terminated. Since your declaration is char course[8], when there are eight characters in the course number, the terminating null is being put off the end of course which lands in the section number, making it zero.
Declaring char course[9] should do the trick.

Answer 2

The 0 is almost certainly the null terminator from this value (and the other values of the same length):
"ENGL1301"
This 8 character string is 9 characters when you include the null terminator at the end of the string. In this case, the null terminator is being written past the end of the string, which happens to be where the section is stored.
To fix this, declare course as char course[9]