Compilare: user.c: In function ‘main’: user.c:15:1: warning: implicit declaration of function ‘fabs’ [-Wimplicit-function-declaration] fprintf(file2, "%.8lf", fabs(M-X)/X); ^ user.c:15:25: warning: incompatible implicit declaration of built-in function ‘fabs’ [enabled by default] fprintf(file2, "%.8lf", fabs(M-X)/X); ^ user.c:12:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%lf", &X); ^ user.c:13:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(file1, "%lf", &M); ^