[讨论]关于头文件写法的疑惑

紫色＆飘蓝ぁ

#include<iostream.h>
和
#include<iostream>
using namespace std;
这两种写法我以前用都可以的 可是最近不知道为什么我用前面的那中写法 老是会出现以下的错误提示
d:\microsoft visual studio\vc98\include\streamb.h(90) : error C2027: use of undefined type 'ios'
d:\microsoft visual studio\vc98\include\streamb.h(67) : see declaration of 'ios'
d:\microsoft visual studio\vc98\include\streamb.h(90) : error C2061: syntax error : identifier 'seek_dir'
d:\microsoft visual studio\vc98\include\istream.h(64) : error C2504: 'ios' : base class undefined
d:\microsoft visual studio\vc98\include\istream.h(118) : error C2027: use of undefined type 'ios'
d:\microsoft visual studio\vc98\include\streamb.h(67) : see declaration of 'ios'
d:\microsoft visual studio\vc98\include\istream.h(118) : error C2061: syntax error : identifier 'seek_dir'
d:\microsoft visual studio\vc98\include\istream.h(118) : error C2535: 'class istream &__thiscall istream::seekg(long)' : member function already defined or declared
d:\microsoft visual studio\vc98\include\istream.h(117) : see declaration of 'seekg'
d:\microsoft visual studio\vc98\include\istream.h(140) : error C2664: 'class ios &(class ios &)' : cannot convert parameter 1 from 'class istream' to 'class ios &'
A reference that is not to 'const' cannot be bound to a non-lvalue
d:\microsoft visual studio\vc98\include\istream.h(155) : error C2065: 'lock' : undeclared identifier
d:\microsoft visual studio\vc98\include\istream.h(155) : error C2065: '