View Compilation Error

0_0_20798187_10559.cpp:1:1: error: 'include' does not name a type
 include <stdio.h>
 ^
0_0_20798187_10559.cpp: In function 'int main()':
0_0_20798187_10559.cpp:7:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&t)!=EOF)  
                        ^
0_0_20798187_10559.cpp:7:27: error: 'EOF' was not declared in this scope
     while(scanf("%d",&t)!=EOF)  
                           ^
0_0_20798187_10559.cpp:13:26: error: 'gcd' was not declared in this scope
             while(gcd(a,c)!=b)  
                          ^
0_0_20798187_10559.cpp:15:28: error: 'printf' was not declared in this scope
             printf("%d\n",c);  
                            ^