Update 557-data-isfile.markdown

Author: Joe7M

_build/reference/557-data-isfile.markdown

@@ -1,7 +1,12 @@
 # ISFILE
 
-> ISFILE (x)
+> b = ISFILE (file)
 
-Returns true if x is a regular file.
+Returns true if the string "f" is a regular file.
 
+### Example
 
+```
+print IsFile("C:\windows\EXPLORER.EXE")        ' Output 1 on Windows, otherwise 0
+print IsFile("/etc/passwd")                    ' Output 1 on Linux, otherwise 0
+```