/in/foo.cc: In function 'int main()':
/in/foo.cc:7:8: error: expected ';' before 'C'
  scanf C=5*(f-32)/9;
        ^
/in/foo.cc:7:20: warning: statement is a reference, not call, to function 'scanf' [-Waddress]
  scanf C=5*(f-32)/9;
                    ^
/in/foo.cc:7:20: warning: statement has no effect [-Wunused-value]
/in/foo.cc:8:18: warning: comparison with string literal results in unspecified behavior [-Waddress]
  printf ("%d%d"=="f"=="%d%d%d%d%d")  
                  ^~~
/in/foo.cc:8:23: warning: comparison with string literal results in unspecified behavior [-Waddress]
  printf ("%d%d"=="f"=="%d%d%d%d%d")  
                       ^~~~~~~~~~~~
/in/foo.cc:8:23: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
/in/foo.cc:8:16: warning: suggest parentheses around comparison in operand of '==' [-Wparentheses]
  printf ("%d%d"=="f"=="%d%d%d%d%d")  
          ~~~~~~^~~~~
/in/foo.cc:8:35: error: cannot convert 'bool' to 'const char*' for argument '1' to 'int printf(const char*, ...)'
  printf ("%d%d"=="f"=="%d%d%d%d%d")  
                                   ^
/in/foo.cc:6:6: warning: unused variable 'C' [-Wunused-variable]
  int C;
      ^