View Compilation Error

0_0_35379838_2829.cpp: In function 'int main()':
0_0_35379838_2829.cpp:14:16: error: 'strlen' was not declared in this scope
   len1=strlen(a);
                ^
0_0_35379838_2829.cpp:18:13: error: 'strcp' was not declared in this scope
    strcp(c,a);
             ^
0_0_35379838_2829.cpp:23:13: error: 'strcp' was not declared in this scope
    strcp(c,b);
             ^