diff --git a/topics/exercises/README.txt b/topics/exercises/README.txt
new file mode 100644
index 00000000..2052f917
--- /dev/null
+++ b/topics/exercises/README.txt
@@ -0,0 +1,8 @@
+while1	- a DCG parser for a fragment of While
+while2	- a DCG parser for While
+while3	- big step semantics for While (+ a DCG parser)
+while4	- small step semantics for While (+ a DCG parser)
+xml1	- a DCG parser for XML subset (elements only)
+xml2	- a DCG parser for XML subset (elements and attributes)
+nb1	- abstract syntax for NB
+nb1	- typed NB abstract syntax
diff --git a/topics/exercises/nb1/Makefile b/topics/exercises/nb1/Makefile
new file mode 100644
index 00000000..97d32b09
--- /dev/null
+++ b/topics/exercises/nb1/Makefile
@@ -0,0 +1,6 @@
+test:
+	swipl -f syntax.pro -t "term(`cat input.txt`)"
+
+prompt:
+	swipl -s syntax.pro
+
diff --git a/topics/exercises/nb1/input.txt b/topics/exercises/nb1/input.txt
new file mode 100644
index 00000000..f477d97d
--- /dev/null
+++ b/topics/exercises/nb1/input.txt
@@ -0,0 +1 @@
+if(iszero(zero),true,succ(zero))
diff --git a/topics/exercises/nb1/syntax.pro b/topics/exercises/nb1/syntax.pro
index b6120594..49a971ea 100644
--- a/topics/exercises/nb1/syntax.pro
+++ b/topics/exercises/nb1/syntax.pro
@@ -1,5 +1,7 @@
+% see slides #109, #113
 term(true).
 term(false).
+term(zero).
 term(succ(T)) :- term(T).
 term(pred(T)) :- term(T).
 term(iszero(T)) :- term(T).
diff --git a/topics/exercises/nb2/Makefile b/topics/exercises/nb2/Makefile
new file mode 100644
index 00000000..179c7355
--- /dev/null
+++ b/topics/exercises/nb2/Makefile
@@ -0,0 +1,7 @@
+test:
+	swipl -f types.pro -t "type(`cat input1.txt`,T),write(T),nl"
+	swipl -f types.pro -t "type(`cat input2.txt`,T),write(T),nl"
+
+prompt:
+	swipl -s types.pro
+
diff --git a/topics/exercises/nb2/input1.txt b/topics/exercises/nb2/input1.txt
new file mode 100644
index 00000000..0843cecc
--- /dev/null
+++ b/topics/exercises/nb2/input1.txt
@@ -0,0 +1 @@
+if(iszero(zero),zero,succ(succ(zero)))
diff --git a/topics/exercises/nb2/input2.txt b/topics/exercises/nb2/input2.txt
new file mode 100644
index 00000000..974ed1ba
--- /dev/null
+++ b/topics/exercises/nb2/input2.txt
@@ -0,0 +1 @@
+if(iszero(zero),iszero(succ(zero)),true)
diff --git a/topics/exercises/nb2/syntax.pro b/topics/exercises/nb2/syntax.pro
new file mode 100644
index 00000000..49a971ea
--- /dev/null
+++ b/topics/exercises/nb2/syntax.pro
@@ -0,0 +1,9 @@
+% see slides #109, #113
+term(true).
+term(false).
+term(zero).
+term(succ(T)) :- term(T).
+term(pred(T)) :- term(T).
+term(iszero(T)) :- term(T).
+term(if(T1,T2,T3)) :- term(T1), term(T2), term(T3).
+
diff --git a/topics/exercises/nb2/types.pro b/topics/exercises/nb2/types.pro
new file mode 100644
index 00000000..d5f79cff
--- /dev/null
+++ b/topics/exercises/nb2/types.pro
@@ -0,0 +1,27 @@
+:- ['syntax.pro'].
+
+%% see slide 126
+% T-True
+type(true,bool).
+
+% T-False
+type(false,bool).
+
+% T-If
+type(if(T1,T2,T3),T) :-
+ type(T1,bool),
+ type(T2,T),
+ type(T3,T).
+
+% T-Zero
+type(zero,nat).
+
+% T-Succ
+type(succ(T),nat) :- type(T,nat).
+
+% T-Pred
+type(pred(T),nat) :- type(T,nat).
+
+% T-Iszero
+type(iszero(T),bool) :- type(T,nat).
+
diff --git a/topics/exercises/while3/mappings.pro b/topics/exercises/while3/mappings.pro
index 7928218e..ec642ea1 100644
--- a/topics/exercises/while3/mappings.pro
+++ b/topics/exercises/while3/mappings.pro
@@ -4,6 +4,8 @@ lookup(M,X,Y) :- append(_,[(X,Y)|_],M).
 % Function update in one position
 update([],X,Y,[(X,Y)]).
 update([(X,_)|M],X,Y,[(X,Y)|M]).
-update([(X1,Y1)|M1],X2,Y2,[(X1,Y1)|M2]) :- \+ X1 = X2, update(M1,X2,Y2,M2).
+update([(X1,Y1)|M1],X2,Y2,[(X1,Y1)|M2]) :-
+ \+ X1 = X2,
+ update(M1,X2,Y2,M2).