Need help on my assignment !!! - about file streams :((
 

I got this code here, i wonder why it doesnt put in the file "in.dat" in the same folder.

#include <stdio.h>

#include <stdlib.h>

#define N 20 //Number of trials



void main(void)

{

FILE * pFile;

float data[N][2];

int i,j ;

char overwrite;



for(i=0;i <= N ; i++)                                                               /* Initinalize the array */

{

        for (j=0; j <= 1; j++)

     data[i][j]= 0;

}





for(i=0; i<=N ; ++i)

{

        printf("%d %5f %5f\n", i, data[i][0], data[i][1]);

}



data[0][1] = -0.545 ;

data[1][1] = 0 ;

data[2][1] = 0 ;

data[3][1] = 0 ;

data[4][1] = 0 ;

data[5][1] = 0 ;

data[6][1] = 0 ;

data[7][1] = 0 ;

data[8][1] = 0 ;

data[9][1] = 0 ;

data[10][1] = 0 ;

data[11][1] = 0 ;

data[12][1] = 0 ;

data[13][1] = 0 ;

data[14][1] = 0 ;

data[15][1] = 0 ;

data[16][1] = 0 ;

data[17][1] = 0 ;

data[18][1] = 0 ;

data[19][1] = 0 ;

data[20][1] = 0 ;



pFile= fopen("C:\\Documents and Settings\\<snipped name>\\My Documents\\Uni Stuff\\Eng Computing\\Sourcecodes\\in.dat","rb");



for(i=0; i<=N; i++)

{

//value[i] = ftell(pFile);

data[i][0] = 5*i;



printf("%f %f\n", data[i][0], data [i][1]);

fprintf(pFile,"%f %f\n", data[i][0], data [i][1]);

}

fclose(pFile);





scanf( "%c", &overwrite);

}

2. Im trying to do this(as said in the assignment):
- Type in the experimental data in a text file and save the file as “in.dat”.

- In the data entry part, use the fscanf() function to read the data from “ïn.dat" file. It is very important that you store the data in a suitable array ( data[N][2] for example). Make sure that all the array's elements are set to zero before you use the array.

This is what i need to put in the file:

0   -0.545

5   0.462

10  2.163

15  4.446

20  7.304

25  10.781

30  14.962

35  19.613

40  25.034

45  30.882

50  37.558

55  44.505

60  52.241

65  60.568

70  69.435

75  78.947

80  89.156

85  99.876

90  111.294

95  123.2

100 135.618

Thanks for helps guys :( I really need it ><

Re: Need help on my assignment !!! - about file streams :((
 

you opened the file for reading, not writeing.

Re: Need help on my assignment !!! - about file streams :((
 

Thanx i realized that. The reason im doing that to input in the file is to get the pointer position so that i can read from the file and get the data in to my arrays. Is there any easier way to do that ?

Re: Need help on my assignment !!! - about file streams :((
 

Open it for reading and writing?

Re: Need help on my assignment !!! - about file streams :((
 

Wat i did is i write the data in first, then open it for reading the data in the file to the array. ;( Trying to figure out, any help ? ><

Re: Need help on my assignment !!! - about file streams :((
 

Just open it for reading and writing. Write to it, read from it.

What's the problem? You can find how fopen works for reading and writing on numerous C reference sites.

Re: Need help on my assignment !!! - about file streams :((
 

Nah thats alright dw about it i fixed the writing reading problem. This is another approach. Index.txt is the file that has the data above.

#include <stdio.h>



#define M 21

#define N 2



void main ()

{

        float a[M][M], x, y;

   FILE *ifp, ;

   int i, j;



   for(i=0; i<M; i++)

   {

           for(j=0;j<N;j++)

      {

              a[i][j]=0;

      }

   }



   ifp=fopen("input.txt", "r");





   for(i=0; i<M; i++)

   {

           for(j=0;j<N;j++)

      {

              fscanf(ifp," %f", &a[i][j]);

         printf("%f\t", a[i][j]);

      }

      printf("\n");

   }









   fclose(ifp);





   getchar();

}

With this code, if M = N then it works (providing the data is in square matrix, which is not suitable for me.

My goal: Input the data from index.txt to the array a[M][N] with M is row and N is collumn.
index.txt

0.000000 -0.545000

5.000000 0.000000

10.000000 0.000000

15.000000 0.000000

20.000000 0.000000

25.000000 0.000000

30.000000 0.000000

35.000000 0.000000

40.000000 0.000000

45.000000 0.000000

50.000000 0.000000

55.000000 0.000000

60.000000 0.000000

65.000000 0.000000

70.000000 0.000000

75.000000 0.000000

80.000000 0.000000

85.000000 0.000000

90.000000 0.000000

95.000000 0.000000

100.000000 0.000000

Re: Need help on my assignment !!! - about file streams :((
 

Instead of using the loops to initialize the array, you can also do it when the array is declared, like this:

float a[M][M] = {0};

The above will initialize all elements of the array to 0.

Re: Need help on my assignment !!! - about file streams :((
 

I still dont understand how my code doesnt work for 21*2 Matrix. , it doesnt read from the file and put in the matrix. Thx for the short way of initializing arrays :p

Re: Need help on my assignment !!! - about file streams :((
 

Two things:
This is a typo:

FILE *ifp, ;

Remove the comma:

FILE *ifp ;

And you might want to read this about void main

The rest of the code looks fine to me. What doesn't work?