View Compilation Error

0_0_33091035_26908.c:2:1: error: expected identifier or '(' before '/' token
 // using namespace std;
 ^
0_0_33091035_26908.c: In function 'main':
0_0_33091035_26908.c:16:5: error: expected expression before '/' token
     // printf("%d",f(5,2));
     ^
0_0_33091035_26908.c:17:5: error: expected expression before '/' token
     // return 0;
     ^
0_0_33091035_26908.c:18:5: error: expected expression before '/' token
     // printf("1234");
     ^