diff --git a/.patches/registers/registers02.cairo.patch b/.patches/registers/registers02.cairo.patch
index ce23b8ad..87e1dc5e 100644
--- a/.patches/registers/registers02.cairo.patch
+++ b/.patches/registers/registers02.cairo.patch
@@ -1,78 +1,16 @@
---- exercises/registers/registers02.cairo	2022-05-18 12:53:44.000000000 -0400
-+++ .tmp_solution/registers02.cairo	2022-05-18 11:40:22.000000000 -0400
-@@ -3,0 +4 @@
-+
-@@ -9,6 +10,2 @@
--func sum_array(array_len : felt, array : felt*) -> (sum : felt):
--    # [ap] = [fp - 4]; ap++
--    # [ap] = [fp - 3]; ap++
--    # [ap] = 0; ap++
--    # call rec_sum_array
--    # ret
-+func sum_array(array_len: felt, array: felt*) -> (sum: felt):
-+    return rec_sum_array(array_len, array, 0)
-@@ -17,16 +14,6 @@
--func rec_sum_array(array_len : felt, array : felt*, sum : felt) -> (sum : felt):
--    # jmp continue if [fp - 5] != 0
--
--    # stop:
--    # [ap] = [fp - 3]; ap++
--    # jmp done
--
--    # continue:
--    # [ap] = [[fp - 4]]; ap++
--    # [ap] = [fp - 5] - 1; ap++
--    # [ap] = [fp - 4] + 1; ap++
--    # [ap] = [ap - 3] + [fp - 3]; ap++
--    # call rec_sum_array
--
--    # done:
--    # ret
-+func rec_sum_array(array_len: felt, array: felt*, sum: felt) -> (sum: felt):
-+    if array_len == 0:
-+        return (sum)
-+    end
-+    
-+    return rec_sum_array(array_len - 1, array + 1, sum + array[0])
-@@ -39,7 +26,31 @@
--func max{range_check_ptr}(a : felt, b : felt) -> (max : felt):
--    # let (res) = is_le(a, b)
--    # if res == 1:
--    #     return (b)
--    # else:
--    #     return (a)
--    # end
-+func max{range_check_ptr}(a: felt, b: felt) -> (max: felt):
-+    # Push arguments to the stack
-+    [ap] = [fp - 5]; ap++ # range_check_ptr
-+    [ap] = [fp - 4]; ap++ # a
-+    [ap] = [fp - 3]; ap++ # b
-+    
-+    # This call will return two values
-+    # 1) the updated range_check_ptr
-+    # 2) 0 or 1 depending on which of a and b is greater
-+    call is_le
-+    
-+    # Push return values to the stack
-+    # There is two of them to push: range_check_ptr and max
-+
-+    # Push the first one, the updated range_check_ptr, onto the stack
-+    [ap] = [ap - 2]; ap++
-+
-+    # Conditional jump
-+    # The following blocks are an assembly level equivalent of the if/else pattern
-+    jmp b_is_more if [ap - 2] !=0 # here [ap-2] is the second value returned by is_le, our boolean
-+    
-+    # Push either a or b to the stack 
-+    a_is_more:
-+    [ap] = [fp - 4]; ap++
-+    jmp done
-+    
-+    b_is_more:
-+    [ap] = [fp -3]; ap++
-+    
-+    done:
-+    ret
-@@ -79 +90 @@
--
-+    
+--- exercises/registers/registers02.cairo	2022-06-11 22:20:43.000000000 -0400
++++ ./registers02.cairo	2022-06-11 22:18:21.000000000 -0400
+@@ -17,3 +17,3 @@
+-    # [ap] = 42; ap++
+-    # [ap - 1] = 42
+-    # [ap - 1] = 21
++    tempvar x = 42
++    assert x = 42
++    assert x = 21
+@@ -27 +27 @@
+-    # assert number = 42
++    [fp -3] = 42
+@@ -37,0 +38 @@
++    assert [p_number] = 42
+@@ -45,0 +47 @@
++    assert 42 = [p_number]
diff --git a/.patches/registers/registers03.cairo.patch b/.patches/registers/registers03.cairo.patch
new file mode 100644
index 00000000..580e7564
--- /dev/null
+++ b/.patches/registers/registers03.cairo.patch
@@ -0,0 +1,78 @@
+--- exercises/registers/registers03.cairo	2022-05-18 12:53:44.000000000 -0400
++++ .tmp_solution/registers03.cairo	2022-05-18 11:40:22.000000000 -0400
+@@ -3,0 +4 @@
++
+@@ -9,6 +10,2 @@
+-func sum_array(array_len : felt, array : felt*) -> (sum : felt):
+-    # [ap] = [fp - 4]; ap++
+-    # [ap] = [fp - 3]; ap++
+-    # [ap] = 0; ap++
+-    # call rec_sum_array
+-    # ret
++func sum_array(array_len: felt, array: felt*) -> (sum: felt):
++    return rec_sum_array(array_len, array, 0)
+@@ -17,16 +14,6 @@
+-func rec_sum_array(array_len : felt, array : felt*, sum : felt) -> (sum : felt):
+-    # jmp continue if [fp - 5] != 0
+-
+-    # stop:
+-    # [ap] = [fp - 3]; ap++
+-    # jmp done
+-
+-    # continue:
+-    # [ap] = [[fp - 4]]; ap++
+-    # [ap] = [fp - 5] - 1; ap++
+-    # [ap] = [fp - 4] + 1; ap++
+-    # [ap] = [ap - 3] + [fp - 3]; ap++
+-    # call rec_sum_array
+-
+-    # done:
+-    # ret
++func rec_sum_array(array_len: felt, array: felt*, sum: felt) -> (sum: felt):
++    if array_len == 0:
++        return (sum)
++    end
++    
++    return rec_sum_array(array_len - 1, array + 1, sum + array[0])
+@@ -39,7 +26,31 @@
+-func max{range_check_ptr}(a : felt, b : felt) -> (max : felt):
+-    # let (res) = is_le(a, b)
+-    # if res == 1:
+-    #     return (b)
+-    # else:
+-    #     return (a)
+-    # end
++func max{range_check_ptr}(a: felt, b: felt) -> (max: felt):
++    # Push arguments to the stack
++    [ap] = [fp - 5]; ap++ # range_check_ptr
++    [ap] = [fp - 4]; ap++ # a
++    [ap] = [fp - 3]; ap++ # b
++    
++    # This call will return two values
++    # 1) the updated range_check_ptr
++    # 2) 0 or 1 depending on which of a and b is greater
++    call is_le
++    
++    # Push return values to the stack
++    # There is two of them to push: range_check_ptr and max
++
++    # Push the first one, the updated range_check_ptr, onto the stack
++    [ap] = [ap - 2]; ap++
++
++    # Conditional jump
++    # The following blocks are an assembly level equivalent of the if/else pattern
++    jmp b_is_more if [ap - 2] !=0 # here [ap-2] is the second value returned by is_le, our boolean
++    
++    # Push either a or b to the stack 
++    a_is_more:
++    [ap] = [fp - 4]; ap++
++    jmp done
++    
++    b_is_more:
++    [ap] = [fp -3]; ap++
++    
++    done:
++    ret
+@@ -79 +90 @@
+-
++    
diff --git a/exercises/registers/registers02.cairo b/exercises/registers/registers02.cairo
index 4f606c09..ee74d6e0 100644
--- a/exercises/registers/registers02.cairo
+++ b/exercises/registers/registers02.cairo
@@ -1,48 +1,46 @@
 %lang starknet
-from starkware.cairo.common.math_cmp import is_le
 
 # I AM NOT DONE
 
+# Cairo memory is immutable.
+# Once a memory cell has been assigned, its value CANNOT be changed.
+# The program will crash if someone tries to assign a new, different, value to an already initialized memory cell.
+# However, trying to assign a memory cell twice, or more, **with the same value** won't cause any harm.
+# This property can be used to assert the value of a cell.
+
 # TODO
-# Rewrite those functions with a high level syntax
-@external
-func sum_array(array_len : felt, array : felt*) -> (sum : felt):
-    # [ap] = [fp - 4]; ap++
-    # [ap] = [fp - 3]; ap++
-    # [ap] = 0; ap++
-    # call rec_sum_array
-    # ret
-end
+# Rewrite this function in a high level syntax, using tempvar and assert
+func crash():
+    # [ap] = 42; ap++
+    # [ap - 1] = 42
+    # [ap - 1] = 21
 
-func rec_sum_array(array_len : felt, array : felt*, sum : felt) -> (sum : felt):
-    # jmp continue if [fp - 5] != 0
+    ret
+end
 
-    # stop:
-    # [ap] = [fp - 3]; ap++
-    # jmp done
+# TODO
+# Rewrite this funtion in a low level syntax
+func assert_42(number : felt):
+    # assert number = 42
 
-    # continue:
-    # [ap] = [[fp - 4]]; ap++
-    # [ap] = [fp - 5] - 1; ap++
-    # [ap] = [fp - 4] + 1; ap++
-    # [ap] = [ap - 3] + [fp - 3]; ap++
-    # call rec_sum_array
+    return ()
+end
 
-    # done:
-    # ret
+# TODO
+# Write this function body so:
+# if the memory cell pointed by `p_number` is not initialized, set it to 42
+# else, if the value is initialized and different from 42, crash
+# else, do nothing and return
+func assert_pointer_42(p_number : felt*):
+    return ()
 end
 
 # TODO
-# Rewrite this function with a low level syntax
-# It's possible to do it with only registers, labels and conditional jump. No reference or localvar
-@external
-func max{range_check_ptr}(a : felt, b : felt) -> (max : felt):
-    # let (res) = is_le(a, b)
-    # if res == 1:
-    #     return (b)
-    # else:
-    #     return (a)
-    # end
+# Write this function body so:
+# if the memory cell pointed by `p_number` is set to 42, do nothing and return
+# else crash
+func assert_pointer_42_no_set(p_number : felt*):
+    return ()
 end
 
 #########
@@ -52,30 +50,82 @@ end
 from starkware.cairo.common.alloc import alloc
 
 @external
-func test_max{range_check_ptr}():
-    let (m) = max(21, 42)
-    assert m = 42
-    let (m) = max(42, 21)
-    assert m = 42
+func test_crash():
+    %{ expect_revert() %}
+    crash()
+
     return ()
 end
 
 @external
-func test_sum():
-    let (array) = alloc()
-    assert array[0] = 1
-    assert array[1] = 2
-    assert array[2] = 3
-    assert array[3] = 4
-    assert array[4] = 5
-    assert array[5] = 6
-    assert array[6] = 7
-    assert array[7] = 8
-    assert array[8] = 9
-    assert array[9] = 10
-
-    let (s) = sum_array(10, array)
-    assert s = 55
+func test_assert_42():
+    assert_42(42)
+
+    %{ expect_revert() %}
+    assert_42(21)
+
+    return ()
+end
+
+@external
+func test_assert_pointer_42_initialized():
+    let (mem_zone : felt*) = alloc()
+    assert mem_zone[0] = 42
+    assert mem_zone[1] = 21
+
+    assert_pointer_42(mem_zone)
+
+    %{ expect_revert() %}
+    assert_pointer_42(mem_zone + 1)
+
+    return ()
+end
+
+@external
+func test_assert_pointer_42_not_initialized_ok():
+    let (mem_zone : felt*) = alloc()
+    assert mem_zone[0] = 42
+    assert_pointer_42(mem_zone)
+
+    assert_pointer_42(mem_zone + 1)
+    assert mem_zone[1] = 42
+
+    return ()
+end
+
+@external
+func test_assert_pointer_42_not_initialized_revert():
+    let (mem_zone : felt*) = alloc()
+    assert mem_zone[0] = 42
+    assert_pointer_42(mem_zone)
+
+    assert_pointer_42(mem_zone + 1)
+    %{ expect_revert() %}
+    assert mem_zone[1] = 21
+
+    return ()
+end
+
+@external
+func test_assert_pointer_42_no_set():
+    let (mem_zone : felt*) = alloc()
+    assert mem_zone[0] = 42
+    assert mem_zone[1] = 21
+
+    assert_pointer_42_no_set(mem_zone)
+
+    %{ expect_revert() %}
+    assert_pointer_42_no_set(mem_zone + 1)
+
+    return ()
+end
+
+@external
+func test_assert_pointer_42_no_set_crash():
+    let (mem_zone : felt*) = alloc()
+
+    %{ expect_revert() %}
+    assert_pointer_42_no_set(mem_zone)
 
     return ()
 end
diff --git a/exercises/registers/registers03.cairo b/exercises/registers/registers03.cairo
new file mode 100644
index 00000000..4f606c09
--- /dev/null
+++ b/exercises/registers/registers03.cairo
@@ -0,0 +1,81 @@
+%lang starknet
+from starkware.cairo.common.math_cmp import is_le
+
+# I AM NOT DONE
+
+# TODO
+# Rewrite those functions with a high level syntax
+@external
+func sum_array(array_len : felt, array : felt*) -> (sum : felt):
+    # [ap] = [fp - 4]; ap++
+    # [ap] = [fp - 3]; ap++
+    # [ap] = 0; ap++
+    # call rec_sum_array
+    # ret
+end
+
+func rec_sum_array(array_len : felt, array : felt*, sum : felt) -> (sum : felt):
+    # jmp continue if [fp - 5] != 0
+
+    # stop:
+    # [ap] = [fp - 3]; ap++
+    # jmp done
+
+    # continue:
+    # [ap] = [[fp - 4]]; ap++
+    # [ap] = [fp - 5] - 1; ap++
+    # [ap] = [fp - 4] + 1; ap++
+    # [ap] = [ap - 3] + [fp - 3]; ap++
+    # call rec_sum_array
+
+    # done:
+    # ret
+end
+
+# TODO
+# Rewrite this function with a low level syntax
+# It's possible to do it with only registers, labels and conditional jump. No reference or localvar
+@external
+func max{range_check_ptr}(a : felt, b : felt) -> (max : felt):
+    # let (res) = is_le(a, b)
+    # if res == 1:
+    #     return (b)
+    # else:
+    #     return (a)
+    # end
+end
+
+#########
+# TESTS #
+#########
+
+from starkware.cairo.common.alloc import alloc
+
+@external
+func test_max{range_check_ptr}():
+    let (m) = max(21, 42)
+    assert m = 42
+    let (m) = max(42, 21)
+    assert m = 42
+    return ()
+end
+
+@external
+func test_sum():
+    let (array) = alloc()
+    assert array[0] = 1
+    assert array[1] = 2
+    assert array[2] = 3
+    assert array[3] = 4
+    assert array[4] = 5
+    assert array[5] = 6
+    assert array[6] = 7
+    assert array[7] = 8
+    assert array[8] = 9
+    assert array[9] = 10
+
+    let (s) = sum_array(10, array)
+    assert s = 55
+
+    return ()
+end
diff --git a/src/exercises/__init__.py b/src/exercises/__init__.py
index f4274ca9..91844698 100644
--- a/src/exercises/__init__.py
+++ b/src/exercises/__init__.py
@@ -25,6 +25,7 @@
     "registers/registers00",
     "registers/registers01",
     "registers/registers02",
+    "registers/registers03",
     "revoked_references/revoked_references01",
     "tricks/no_conditionals",
     "tricks/assert_bool",