Thread: Writing C

Hi,

I am new to C programming and MATLAB but I have a class and an assignment to write a C program for following:

a. read a data file (filename.txt) which has 2 arrays A and B
- A is 5x4 and B is 4x5 matrix
b. calculate F=AxB and solution should be 5x5 matrix
c. print F into a filename.txt

This is what I have as shown by prof in a way...is this correct and how do I do b. and c.? Thnx

Code:

#include "stdio.h"
main()

FILE *fin;
fopen(fin)
fscanf(fin, '%d %d', &row, &column);
for (i=0; i<row; i++);
    {
        fscanf(fin, '%f %f %f %f', &a, %b, %c, %d);
    ArrayA[i][0]=a;
    ArrayB[i][1]=b;
    ArrayC[i][2]=c;
    ArrayD[i][3]=d;
    }
for (i=0; i<column; i++);
    {
        fscanf(fin, '%f %f %f %f %f', &a, &b, &c, &d, &e);
    ArrayA[i][0]=a;
    ArrayB[i][1]=b;
    ArrayC[i][2]=c;
    ArrayD[i][3]=d;
    ArrayE[i][4]=e;
    }

Originally Posted by quzah

Does it work? No. Then it's not the right way to do it.

1. main returns an int, and so you need a return 0; at the bottom of your main function.

2. main, if it is to take no argumetns, should be main( void ).

3. Functions needs a pair of braces to enclose their contents, you don't have any.

4. You don't assign the return value of fopen so you can't do anything with the file in the event it actually opens.

5. You haven't actually declared any arrays. Even if you did, you'd be declaring way too many.

6. You didn't declare i either. (or a, b, c, ...)

7. You didn't even try to compile this, because if you had, your compiler would be having a fit.


Quzah.

Thank you for reply.
I know it doesn't work but I it is all confusing to me as I never did this, total newbie. I'm searching how to read a file which has matrix in it and calculating it into another file. Everybody has some different ways of writing these codes; makes no sense to me.

This guy that teaches us doesn't really give us much besides already done examples and nothing on how to begin to write a program.

I have written this now. Any inputs on how to continue on with the problem? Thanks

Code:

#include "mex.h"
#include "stdio.h"

//void mexFunction (int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
main(void)

{
    File *fin;
    int i, j;
    float A[5],B[4];
    float a,b;
    
    fin = fopen("et7450hw1inA.txt","r");
    
    fscanf(fin, "%d %d", &row, &column);
    for(i=0; i<row; i++)
    {
        fscanf(fin, "%f %f %f %f", &a, &b, &c, &d);
        ArrayA[i][0]=a;
        ArrayB[i][1]=b;
    }

You should ever check the return-value from fscanf.

Originally Posted by Zvezda

This guy that teaches us doesn't really give us much besides already done examples and nothing on how to begin to write a program.

You're best choices...

1) Get a different teacher.
2) Get an actual textbook and study it.
3) Do both.


I'm beginning to think that a lot of the people out there teaching C have never actually programmed in C... they're following a curriculum and spouting crap from some ancient textbook... Not exactly the best start to a programming career... (Which is why I've always thought that programming should be learned by apprentiship...)

Originally Posted by CommonTater

You're best choices...

1) Get a different teacher.
2) Get an actual textbook and study it.
3) Do both.


I'm beginning to think that a lot of the people out there teaching C have never actually programmed in C... they're following a curriculum and spouting crap from some ancient textbook... Not exactly the best start to a programming career... (Which is why I've always thought that programming should be learned by apprentiship...)

I think that too but we can't do much about it. We don't have a book for the class; just what he gives us. Anyhow, I don't have time to learn this thing from scratch. I did read some stuff of net but it's confusing to put everything together.
I'm not in programming business but it's my masters class. I don't plan on working with this or anything; just need to pass and go on.

Originally Posted by Zvezda

I think that too but we can't do much about it. We don't have a book for the class; just what he gives us. Anyhow, I don't have time to learn this thing from scratch. I did read some stuff of net but it's confusing to put everything together.
I'm not in programming business but it's my masters class. I don't plan on working with this or anything; just need to pass and go on.

How much is your future worth to you? Amazon.com: C Programming Language

Originally Posted by ChipS

I agree with CommonTater, I've recently graduated and I have to say that my programming professors at university were just shy of horrible. My community college professors with actual work experience were much better. I'm in the process of reteaching myself C and C++ in order to fill the many gaps my formal education has left me with.

And even then you need to realize that texts such as K&R's C Programming Language do not cover the entirety of the language or it's capabilities. They are excellent introductions but there is at least equal value in compiler related documentation which is generally a full disclosure of what the compiler and it's libraries can do for you... Contary to common belief programmers don't memorize everything, or even try to, it's all about "looking stuff up" when you need it.

Originally Posted by CommonTater

And even then you need to realize that texts such as K&R's C Programming Language do not cover the entirety of the language or it's capabilities. They are excellent introductions but there is at least equal value in compiler related documentation which is generally a full disclosure of what the compiler and it's libraries can do for you... Contary to common belief programmers don't memorize everything, or even try to, it's all about "looking stuff up" when you need it.

Agreed. I forgot to mention that I also have a C reference book that I never plan on reading cover to cover and I'm sure I'll need to add to my reference collection throughout my career. I feel that introductory texts are extremely helpful though.

Thank you very much for info guys. I appreciate it.

Anyhow, here is my latest code, which still needs a lot code added to but it could be a good start.
Again, this code needs to run a program which does:
a. read a data file (filename.txt) which has 2 arrays A and B
- A is 5x4 and B is 4x5 matrix
b. calculate F=AxB and solution should be 5x5 matrix
c. print F into a filename.txt

Code:

#include "stdio.h"

main(void)
{
    FILE *Fin, *Fout;
    int row, column, i, j;
    float ArrayA[5][4];
    float ArrayB[4][5];
    
    Fin = fopen("et7450hw1inA.txt","r");
    fscanf(Fin, '%d %d', &row, &column);
    for (i=0; i<row; i++);
    {
        if ArrayA[1][2]==0
        {
            break;
        }
    }
    {   
fscanf(fin, "%f %f %f %f", &a, &b, &c, &d);
ArrayA[i][0]=a;
ArrayB[i][1]=b;
ArrayC[i][2]=c;
ArrayD[i][3]=d;
    
    fclose(Fin);
    return 0;
    }
}

Question: At the end, I'm not sure if I have to use fclose or return?
Also, when I try to run it, it says Undefined function or variable?? Why?

Help much appreciated.

Originally Posted by ChipS

Agreed. I forgot to mention that I also have a C reference book that I never plan on reading cover to cover and I'm sure I'll need to add to my reference collection throughout my career. I feel that introductory texts are extremely helpful though.

Trust me... a deliberate study --cover to cover-- is an enormous benfit, even if you already think you're pretty good.
You just never know what you might actually learn...