I have written a program which calculates matrices. Now I want to use those calculated matrices. So I want my C++ programm to generate a file on my computer and to copy the calculated matrix to this new file. Does anybody know how to do this?

Have you tried using a map of vectors? map being your columns and the vector holding data for each column

#include<stdio.h> int mat[3][3] = {{1, 2, 3}, {4,5,6},{7,8,9}}; main() { int i, j; mat2[3][3]; /*Write matrix to file*/ FILE *fp = fopen("matrix.txt", "w"); for(i=0; i<3; i++) for(j=0;j<3; j++) fprinf(fp, "%d\n", mat[i][j]); fclose(fp); /*Read matrix back from file*/ fp = fopen("matrix.txt", "r"); for(i=0; i<3; i++) for(j=0;j<3; j++) fscanf(fp, "%d", &mat2[i][j]); fclose(fp); } Santanu Sen National Institute of Technology Durgapur India