kc3-lang/kc3

diff --git a/doc/1_KC3/1.10_Bool.en.md b/doc/1_KC3/1.10_Bool.en.md
index 8d65f13..dd9588e 100644
--- a/doc/1_KC3/1.10_Bool.en.md
+++ b/doc/1_KC3/1.10_Bool.en.md
@@ -1 +1,37 @@
 # 1.10 Bool
+
+Booleans can have only two values : `false` or `true`.
+
+They can be casted to integer types, `false` being `0` and
+true being `1`.
+
+You can cast any type to a boolean : integers `0` and character NUL
+being `false` and everything else being `true`. This is useful for
+boolean operations : accept any tag as a condition and if it
+evaluates to `true` after a cast then proceed. This is how
+`if_then_else` and `while` and many KC3 operators are implemented.
+
+## 1.10.1 Examples
+
+```
+ikc3> true && true
+true
+ikc3> true && false
+false
+ikc3> if "" do "ok" else "ko" end
+"ok"
+ikc3> if 1 do "ok" else "ko" end
+"ok"
+ikc3> if 0 do "ko" else "ok" end
+"ok"
+ikc3> (Bool) ""
+true
+ikc3> (Bool) 1
+true
+ikc3> (Bool) 0
+false
+ikc3> "ok" == "ok"
+true
+ikc3> "ok" == "ko"
+false
+```