You may have a look at some C++ specification (or if you do not want to spend money for it, on a draft of it, e.g.
Working Draft, Standard for Programming Language C++[
^]).
See section "17.6.1.2 Headers":
[...] the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in the C standard library [...]. In the C++ standard library, however, the declarations (except for names which are defined as macros in C) are within namespace scope [...] of the namespace std. [...]
The C++ headers as well as the C headers then are listed in separate tables:
C++ library headers
| <algorithm> | <fstream> | <list> | <regex> | <typeindex> |
| <array> | <functional> | <locale> | <set> | <typeinfo> |
| <atomic> | <future> | <map> | <sstream> | <type_traits> |
| <bitset> | <initializer_list> | <memory> | <stack> | <unordered_map> |
| <chrono> | <iomanip> | <mutex> | <stdexcept> | <unordered_set> |
| <codecvt> | <ios> | <new> | <streambuf> | <utility> |
| <complex> | <iosfwd> | <numeric> | <string> | <valarray> |
| <condition_variable> | <iostream> | <ostream> | <strstream> | <vector> |
| <deque> | <istream> | <queue> | <system_error> |
| <exception> | <iterator> | <random> | <thread> |
| <forward_list> | <limits> | <ratio> | <tuple> |
C library headers
| <cassert> | <cinttypes> | <csignal> | <cstdio> | <cwchar> |
| <ccomplex> | <ciso646> | <cstdalign> | <cstdlib> | <cwctype> |
| <cctype> | <climits> | <cstdarg> | <cstring> |
| <cerrno> | <clocale> | <cstdbool> | <ctgmath> |
| <cfenv> | <cmath> | <cstddef> | <ctime> |
| <cfloat> | <csetjmp> | <cstdint> | <cuchar> |
Appendix D.5 details using the "old-style" C header files.
[...] For compatibility with the C standard library [...], the C++ standard library provides the 25 C headers [...]
C headers
| <assert.h> | <inttypes.h> | <signal.h> | <stdio.h> | <wchar.h> |
| <complex.h> | <iso646.h> | <stdalign.h> | <stdlib.h> | <wctype.h> |
| <ctype.h> | <limits.h> | <stdarg.h> | <string.h> |
| <errno.h> | <locale.h> | <stdbool.h> | <tgmath.h> |
| <fenv.h> | <math.h> | <stddef.h> | <time.h> |
| <float.h> | <setjmp.h> | <stdint.h> | <uchar.h> |
[...] Every C header, each of which has a name of the form name.h, behaves as if each name placed in the standard library namespace by the corresponding cname header is placed within the global namespace scope. [...]
Cheers
Andi
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