Pray god guide!!!!!!
The first file

//external. CPP -- -- external variables 
//the compile with support. CPP 
#include  
using namespace std; 
//external variable 
Double warming=0.3;//warming defined 
//function as 
Void the update (double dt); 
Void local (); 

Int main () 
{
cout <"Global warming is" & lt; The update (0.1); 
cout <"Global warming is" & lt; Local (); 
cout <"Global warming is" & lt; return 0; 
} 

The second file

//support. The CPP -- -- use external variable 
//the compile with external. CPP 
#include  
Extern double warming;//use warming form another file 

//function as 
Void the update (double dt); 
Void local (); 

Using STD: : cout; 
Void the update (double dt) 
{
Extern double warming;//optional redeclaration 
Warming +=dt;//USES global warming 
cout <"Updating global warming to" & lt; cout <"Degrees. \ n"; 
} 

Void local () 
{
Double warming=0.8; 

cout <"Local warming=" & lt; cout <"But global warming=" & lt; <: : warming & lt; <"Degrees. \ n"; 
} 

Compilation is not through, this problem!!!!!!


Still need to debug after


C: \ Users \ wulc1 \ AppData \ Local \ Temp \ cczMrAQE o: function In ` main ':
F:/git/9.5 _external. CPP: 14: undefined reference to ` update (double)
'F:/git/9.5 _external. CPP: 16: undefined reference to ` local ()
'Collect2. Exe: error: ld returned 1 exit status
Pray god guide!!!!!!