View Compilation Error

In file included from 0_0_15495676_8945.cpp:1:0:
0_0_15495676_8945.cpp: In function 'int main()':
0_0_15495676_8945.cpp:5:20: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
     while(gets(a)!=EOF)
                    ^
0_0_15495676_8945.cpp:7:25: error: 'strlen' was not declared in this scope
         int i,b=strlen(a);
                         ^