View Compilation Error

0_0_35146639_8560.cpp: In function 'int main()':
0_0_35146639_8560.cpp:31:23: error: 'strlen' was not declared in this scope
         buf[strlen(buf)-1] = '\0';
                       ^
0_0_35146639_8560.cpp:32:29: error: 'strcmp' was not declared in this scope
         if (strcmp(buf, "-1") == 0)
                             ^
0_0_35146639_8560.cpp:42:28: error: 'strcpy' was not declared in this scope
         strcpy(words[0], "");
                            ^
0_0_35146639_8560.cpp: In function 'void process(char*)':
0_0_35146639_8560.cpp:140:24: error: 'strlen' was not declared in this scope
     int    l = strlen(p);
                        ^
0_0_35146639_8560.cpp:150:31: error: 'strcpy' was not declared in this scope
             strcpy(words[k], p);
                               ^