c'è stato un problema di copia e incolla,nonostante tutto questi sono gli errori che mi dava:
	codice:
	#include <iostream>
#include <time.h>
#include <stdlib.h>
#include <iomanip>
int main()
{
    srand(time(NULL));
    int x=rand()%6+1;
    switch (x) {
        case 1:
            cout<<x<<") Lunedi";
            break;
        case 2:
            cout<<x<<") Martedi";
            break;
        case 3:
           cout<<x<<") Mercoledi";
            break;
        case 4:
            cout<<x<<") Giovedi";
            break;
        case 5:
            cout<<x<<") Venerdi";
            break;
        case 6:
            cout<<x<<") Sabato";
            break;
        case 7:
            cout<<x<<") Domenica";
            break;
    }
        return 0;
}
 
	codice:
	prog.cpp: In function ‘int main()’:
prog.cpp:13:13: error: ‘cout’ was not declared in this scope
             cout<<x<<") Lunedi";
             ^
prog.cpp:13:13: note: suggested alternative:
In file included from prog.cpp:1:0:
/usr/include/c++/4.8/iostream:61:18: note:   ‘std::cout’
   extern ostream cout;  /// Linked to standard output