Eroare de compilare: user.c: In function 'main': user.c:6: warning: implicit declaration of function 'freopen' user.c:6: error: 'stdin' undeclared (first use in this function) user.c:6: error: (Each undeclared identifier is reported only once user.c:6: error: for each function it appears in.) user.c:7: error: 'stdout' undeclared (first use in this function) user.c:9: warning: implicit declaration of function 'scanf' user.c:9: warning: incompatible implicit declaration of built-in function 'scanf' user.c:16: error: 'ok' undeclared (first use in this function) user.c:23: error: expected expression before '<<' token user.c:26: warning: implicit declaration of function 'printf' user.c:26: warning: incompatible implicit declaration of built-in function 'printf' user.c:29:4: warning: no newline at end of file