Add extern notes to C.

1 files changed, 7 insertions, 1 deletions

diff --git a/c.html.markdown b/c.html.markdown
index ee60d168..2a828ab7 100644
--- a/c.html.markdown
+++ b/c.html.markdown
@@ -99,7 +99,7 @@ int main() {
     unsigned int ux_int;
     unsigned long long ux_long_long;
 
-    // chars inside single quotes '*' are ASCII versions of  
+    // chars inside single quotes '*' are character constants. 
     '0' //==> 48 on the ASCII table. 
     'A' //==> 65 on the ASCII table. 
 
@@ -472,6 +472,12 @@ while ((c = getchar()) != EOF) { // EOF constant "end of file".
     char c = getchar(); 
 }
 
+//if referring to external variables outside function, must use extern keyword.
+int i = 0;
+void testFunc() {
+    extern int i; //i here is now using external variable i
+}
+
 /*
 char c[] = "This is a test.";
 str_reverse(c);