day1010110

Hi!
I'm a newbie at programming c. I'm currently working thru the steps of a introduction to c, as preparation for future assignments for a neural networks course. Unfortantly the steps in the introduction aren't really suited for someone who's new to the programming language I'm trying to write a program that reads in two vectors/arrays and computes their dot product. Most is working, but I have no idea how to create a datafile like the following: So, generate a file (with a header and with data) something like:

5
0.3 4.5
1.9 2.3
3.3 1.178
3.2 4.5
0.19 99.99

First of, what's a header? Is it the #include <stdio.h> stuff, should I put that at the beginning of the data file? Or does it mean i should make some kind of .h file for libaries (read something like that in a tutorial on the web)? And can I simple copy paste this data into the file? So far I have the following program to read the datafile:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main (int argc, char *argv[])
{
FILE *fp;
int n;

if (argc!=2) {
fprintf(stderr,"use: inprod 'fname'!\n");
exit(1);
}
if ((fp=fopen(argv[1],"r"))==NULL) {
fprintf(stderr,"unable to open '%s' for reading!\n",argv[1]);
exit(1);
}
fp = fopen(argv[1], "r");
fscanf(fp,"%d",&n);
printf("%d",n);

/* and here you should loop over n to read the x[i] and w[i] */
}
The printf is meant to check what it's reading and shoul produce the number 5, but instead I get 1108551892, which I guess is some kind of memory location(?).
Can anybody here please explain to me (in baby steps :o ) what I need to do or am doing wrong? I'll be eternally gratefull!
For completeness sake, below the computing part of my programm:
(BTW I have a sneaking suspicion that it won't work on the datafile in it's current format, even if I can read it in)
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define MAXLENGTH 16
double w[MAXLENGTH], x[MAXLENGTH], y[MAXLENGTH];

int main (int argc, char *argv[])
{

int n;
int i;
double z;
double total = 0;

printf("Welcome to my first C-program!");
printf("please type the length of the vector 'w':");
fflush(stdout);

for (i = 0; i < MAXLENGTH; i++)
scanf ("%lf",&w[i]);
for (i = 0; i < MAXLENGTH; i++)
printf("w [%d] = %lf \n", i, w[i]);

printf("please type the length of the vector 'x':");
fflush(stdout);

for (i = 0; i < MAXLENGTH; i++)
scanf ("%lf",&x[i]);
for (i = 0; i < MAXLENGTH; i++)
printf("x [%d] = %lf \n", i, x[i]);

/*maakt een lijst y met de producten van de elementen uit lijst w en x */
for (i=0; i<MAXLENGTH; i++)
y[i] = w[i] * x[i];

for (i=0; i<MAXLENGTH; i++)
printf ("y[%d] = %lf\n",i, y[i]);

/*Telt de elementen uit lijst y bij elkaar op */
for (i=0; i<MAXLENGTH; i++)
total += y[i];

printf ("het inproduct is %lf\n",total);

return 0;

}

day1010110

Yeeh, I solved it myself! Am over the moon right now....what a good feeling
This is my final, working code:
with the accompanying data file(test.dat):

Probably not the most compact code to do this, but I'm just so happy it works!