View Compilation Error

0_0_20730208_8052.cpp: In function 'int main()':
0_0_20730208_8052.cpp:12:25: error: 'strlen' was not declared in this scope
         int m = strlen(s),a[5] = {0};  
                         ^
0_0_20730208_8052.cpp:16:21: error: 'a' was not declared in this scope
                     a[0]++;  
                     ^
0_0_20730208_8052.cpp:18:21: error: 'a' was not declared in this scope
                     a[1]++;  
                     ^
0_0_20730208_8052.cpp:20:21: error: 'a' was not declared in this scope
                     a[2]++;  
                     ^
0_0_20730208_8052.cpp:22:21: error: 'a' was not declared in this scope
                     a[3]++;  
                     ^
0_0_20730208_8052.cpp:24:21: error: 'a' was not declared in this scope
                     a[4]++;  
                     ^
0_0_20730208_8052.cpp:26:21: error: 'a' was not declared in this scope
         cout<<"a:"<<a[0]<<endl;  
                     ^