View Compilation Error

0_0_18398050_12181.cpp: In function 'int findd(char*)':
0_0_18398050_12181.cpp:15:30: error: 'strcmp' was not declared in this scope
         if(strcmp(s,nn[i].str)==0)
                              ^
0_0_18398050_12181.cpp:21:25: error: 'strcpy' was not declared in this scope
     strcpy(nn[num].str,s);
                         ^
0_0_18398050_12181.cpp: In function 'int main()':
0_0_18398050_12181.cpp:49:30: error: 'strlen' was not declared in this scope
             int len=strlen(ss);
                              ^