Compilare: user.c: In function ‘main’: user.c:9:18: warning: passing argument 1 of ‘fopen’ from incompatible pointer type [-Wincompatible-pointer-types] f1=fopen(stdin,"r"); ^~~~~ In file included from user.c:1:0: /usr/include/stdio.h:272:14: note: expected ‘const char * restrict’ but argument is of type ‘struct _IO_FILE *’ extern FILE *fopen (const char *__restrict __filename, ^~~~~ user.c:10:18: warning: passing argument 1 of ‘fopen’ from incompatible pointer type [-Wincompatible-pointer-types] f2=fopen(stdout,"w"); ^~~~~~ In file included from user.c:1:0: /usr/include/stdio.h:272:14: note: expected ‘const char * restrict’ but argument is of type ‘struct _IO_FILE *’ extern FILE *fopen (const char *__restrict __filename, ^~~~~ user.c:17:5: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f1,"%d%d",&A,&B); ^~~~~~~~~~~~~~~~~~~~~~~ user.c:18:22: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] for(i=0;i<A;i++) fscanf(f1,"%d",&a[i]); ^~~~~~~~~~~~~~~~~~~~~ user.c:19:22: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] for(i=0;i<B;i++) fscanf(f1,"%d",&b[i]); ^~~~~~~~~~~~~~~~~~~~~