Parsing a CSV File Problems - c

Question

I tried this to parse data given in a csv file into ID, AGE, and GPA fields in a "data" file, but I don't think I'm doing this right (when I tried printing the data, its printing weird numbers). What am I doing wrong?
char data[1000];
FILE *x = fopen("database.csv","rt");
char NAME[300];
int ID[300],AGE[300],GPA[300];
int i,j;
i = 0;
while(!feof(x)) {
fgets(data,999,x);
for (j = 0; j < 300 && data[i] != ','; j++, i++) {
ID[j] = data[i];
i++;
}
for (j = 0; j < 300 && data[i] != ','; j++, i++) {
NAME[j] = data[i];
i++;
}
for (j = 0; j < 300 && ( data[i] != '\0' || data[i] != '\r' || data[i] != data[i] != '\n'); j++, i++) {
GPA[j] = data[i];
}
}

Answer 1

First of all: for what you're doing, you probably want to look carefully at the function strtok and the atoi macro. But given the code you posted, that's perhaps still a bit too advanced, so I'm taking a longer way here.
Supposing that the line is something like
172,924,1182
then you need to parse those numbers. The number 172 is actually represented by two or four bytes in memory, in a very different format, and the byte "0" is nothing like the number 0. What you'll read is the ASCII code, which is 48 in decimal, or 0x30 in hex.
If you take the ASCII value of a single digit and subtract 48, you will get a number, because fortunately the numbers are stored in digit order, so "0" is 48, "1" is 49 and so on.
But you still have the problem of converting the three digits 1 7 2 into 172.
So once you have 'data':
(I have added commented code to deal with a unquoted, unescaped text field inside the CSV, since in your question you mention an AGE field, but then you seem to want to use a NAME field. The case when the text field is quoted or escaped is another can of worms entirely)
size_t i = 0;
int number = 0;
int c;
int field = 0; // Fields start at 0 (ID).
// size_t x = 0;
// A for loop that never ends until we issue a "break"
for(;;) {
c = data[i++];
// What character did we just read?
if ((',' == c) || (0x0c == c) || (0x0a == c) || (0x00 == c)) {
// We have completed read of a number field. Which field was it?
switch(field) {
case 0: ID[j] = number; break;
case 1: AGE[j] = number; break;
// case 1: NAME[j][x] = 0; break; // we have already read in NAME, but we need the ASCIIZ string terminator.
case 2: GPA[j] = number; break;
}
// Are we at the end of line?
if ((0x0a == c) || (0x0c == c)) {
// Yes, break the cycle and read the next line
break;
}
// Read the next field. Reinitialize number.
field++;
number = 0;
// x = 0; // if we had another text field
continue;
}
// Each time we get a digit, the old value of number is shifted one order of magnitude, and c gets added. This is called Horner's algorithm:
// Number Read You get
// 0 "1" 0*10+1 = 1
// 1 "7" 1*10+7 = 17
// 17 "2" 17*10+2 = 172
// 172 "," Finished. Store 172 in the appropriate place.
if (c >= '0' && c <= '9') {
number = number * 10 + (c - '0');
}
/*
switch (field) {
case 1:
NAME[j][x++] = c;
break;
}
*/
}