View Compilation Error

0_0_30828359_12825.cpp: In function 'void boss_newboss()':
0_0_30828359_12825.cpp:12:24: error: 'strlen' was not declared in this scope
  newbosskey=strlen(boss)/2;
                        ^
0_0_30828359_12825.cpp: In function 'void boss_news(int)':
0_0_30828359_12825.cpp:33:23: error: 'strlen' was not declared in this scope
  for(i=0;i<strlen(boss);i++)
                       ^
0_0_30828359_12825.cpp:39:39: error: 'strlen' was not declared in this scope
  int pass[MAX];int passkey=strlen(boss)/2;
                                       ^
0_0_30828359_12825.cpp: In function 'int main()':
0_0_30828359_12825.cpp:121:43: error: 'strlen' was not declared in this scope
   boss_newboss();int i=1;int n=strlen(boss);int sameflag=1;
                                           ^