View Compilation Error

0_0_36270822_2589.cpp: In function 'int main()':
0_0_36270822_2589.cpp:14:27: error: 'strcmp' was not declared in this scope
 while(gets(s),strcmp(s,"0"))
                           ^
0_0_36270822_2589.cpp:16:18: error: 'strlen' was not declared in this scope
 for(i=(j=strlen(s))-1;i>=0;i--)
                  ^