View Compilation Error

0_0_21679001_1476.cpp: In function 'int main()':
0_0_21679001_1476.cpp:20:29: error: 'strlen' was not declared in this scope
         len=strlen(matrix[0]);
                             ^
0_0_21679001_1476.cpp: At global scope:
0_0_21679001_1476.cpp:55:2: error: expected unqualified-id before '<' token
 }</textarea> 
  ^