Thread: looked at tutorial and still confused

i have file pointer and i think an array, i just dnt know what number to use in the brackets.
the i have to filepoint this file to my program.
inputf.dat which is the following matrix or set of numbers

1.0 1.0 -4.0 -0.5
-2.0 1.5 1.0 2.1
-1.1 0.7 -2.5 4.2
2.4 0.3 0.4 -1.9
0.8 1.2 -0.9 -0.5

input_1=fopen("inputf.dat", "r")
if(input_1==NULL) exit(1);

int m=0; j, i, n;
char line[?]; <-this is my question. what number do i type here?

by the way if this is what im suppose to do.
By using a pointer to pointer **A and the function calloc()
allocate the memory for the 4x4 matrix A[][].
By using a pointer *x and the function malloc()
allocate the memory for the 4-dimensional vector x[].
Read the components of A and x from the given input file inputf.dat
(which is in the public directory; you need to copy it into your directory).
The last line of the input file contains the components of x. The rows of
matrix A are the first four lines of the input file. Print the components
of A[][] and x[]
all i need to know is what number belongs in the bracket

the purpose is to input the data into my program right?

Well, what do you suppose the maximum length of a line will be from your file? That array has to be large enough to hold that length.

And if you're asking these questions, this assignment probably exceeds your capabilities.

well this is the other part i didnt add hopefully this helps

char line[?];
double **A, *x;
A=(double **)calloc(4,sizeof(double *));
for(i=0;i<4;i++)
A[i]=(double *)calloc(4 ,sizeof(double));
x=(double *)malloc(4*sizeof(double));

okay that helps thanks, i finished the rest but the thing is now, i do not know how to write the program for the transpose A_s. which the formula used ismatrix A_s=(A+A_t)/2

the normal matrix i obtained with this
insert

Code:

 char line[64];
 double **A, *x;
 A=(double **)calloc(4,sizeof(double *));
 for(i=0;i<4;i++)
 A[i]=(double *)calloc(4 ,sizeof(double));
 x=(double *)malloc(4*sizeof(double));
 
 while(fgets(line,64,input_1,) != NULL
 {
  if(k==4) sscanf(line, "%lf %lf %lf %lf", &x[0],&x[1],&x[2],&x[3]);
  else
   {
   sscanf(line, "%lf %lf %lf %lf", &A[m][0],&A[m][1],&A[m][2],&A[m][3]);
   }
  m++;
 
 }
 
printf("Matrix A is:");
printf("\n\n");
for(q=0;q<4;q++)
printf("%6.3f ",A[0][q]);
printf("\n");

for(j=0;j<4;j++)
printf("%6.3f ",A[1][q]);
printf("\n");

for(j=0;j<4;j++)
printf("%6.3f ",A[2][q]);
printf("\n");

for(j=0;j<4;j++)
printf("%6.3f ",A[3][q]);
printf("\n\n");

printf("Vector x is:");
printf("\n\n");
printf(" x[] =  ");
for(j=0;j<4;j++)
printf("%6.3f  ",x[q]);
printf("\n\n");

and then its

smatrix(A,x,n);
here is where i dnt know how to make it transpose
am i just suppose to switch A[#][q] to [q]A[#]

the class is called mae9 c/c++

we are using c++