View Compilation Error

0_0_27863940_20996.cpp: In function 'int main()':
0_0_27863940_20996.cpp:13:64: error: 'strlen' was not declared in this scope
         for(i=0;i<n;i++)p[i]=i,gets(dic[i]),tlen+=strlen(dic[i]);
                                                                ^
0_0_27863940_20996.cpp:24:37: error: 'strcat' was not declared in this scope
                 strcat(tmp,dic[p[i]]);
                                     ^
0_0_27863940_20996.cpp:26:28: error: 'strcpy' was not declared in this scope
             strcpy(ttmp,tmp);
                            ^
0_0_27863940_20996.cpp:27:28: error: 'strcat' was not declared in this scope
             strcat(ttmp,tmp);
                            ^
0_0_27863940_20996.cpp:33:37: error: 'strcmp' was not declared in this scope
                 if(strcmp(ttmp+i,tmp)==0)
                                     ^