Miscellany

blah.cpp: In function ‘int main()’:
blah.cpp:20:21: error: no match for ‘operator<=’ in ‘grade <= 60’
blah.cpp:25:20: error: no match for ‘operator>’ in ‘grade > 61’
blah.cpp:25:35: error: no match for ‘operator<=’ in ‘grade <= 70’
blah.cpp:27:50: error: no match for ‘operator<=’ in ‘std::basic_string<_CharT, _Traits, _Alloc>::substr(std::basic_string<_CharT, _Traits, _Alloc>::size_type, std::basic_string<_CharT, _Traits, _Alloc>::size_type) const [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>, std::basic_string<_CharT, _Traits, _Alloc> = std::basic_string<char>, std::basic_string<_CharT, _Traits, _Alloc>::size_type = unsigned int](1u, 1u) <= 3’
blah.cpp:28:32: error: ‘strcat’ is not a member of ‘std’
blah.cpp:28:59: error: expected ‘;’ before ‘}’ token
blah.cpp:29:61: error: expected ‘)’ before ‘{’ token
blah.cpp:53:55: error: could not convert ‘std::basic_string<_CharT, _Traits, _Alloc>::substr(std::basic_string<_CharT, _Traits, _Alloc>::size_type, std::basic_string<_CharT, _Traits, _Alloc>::size_type) const [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>, std::basic_string<_CharT, _Traits, _Alloc> = std::basic_string<char>, std::basic_string<_CharT, _Traits, _Alloc>::size_type = unsigned int](1u, 1u).std::basic_string<_CharT, _Traits, _Alloc>::operator= [with _CharT = char, _Traits = std::char_traits<char>, _Alloc = std::allocator<char>, std::basic_string<_CharT, _Traits, _Alloc> = std::basic_string<char>](1)’ to ‘bool’
blah.cpp:56:1: error: expected primary-expression before ‘}’ token
blah.cpp:56:1: error: expected ‘;’ before ‘}’ token