View Compilation Error

0_0_13763176_13113.cpp: In function 'int main(int, char**)':
0_0_13763176_13113.cpp:12:25: error: 'memset' was not declared in this scope
   memset(c3,0,sizeof(c3));
                         ^
0_0_13763176_13113.cpp:16:18: error: 'strlen' was not declared in this scope
   for(i=strlen(c1)-1,j=strlen(c2)-1;i>=0&&j>=0;){
                  ^