diff --git a/bitutilities.py b/bitutilities.py
index e8179fe..8702e0d 100644
--- a/bitutilities.py
+++ b/bitutilities.py
@@ -68,7 +68,7 @@ def get_memory(variable_name: str) -> list[bool]:
 
 
 def binary_sum(first_term: BasicRegister, second_term: BasicRegister, return_remainder: bool = False)\
-        -> BasicRegister | tuple[BasicRegister, int]:
+        -> BasicRegister or tuple[BasicRegister, int]:
     """
     Sums two registers' values.
 
@@ -103,6 +103,37 @@ def binary_sum(first_term: BasicRegister, second_term: BasicRegister, return_rem
     c.memory[0] = bool(final_bit_sum & 1)
 
     if return_remainder:
-        return c, carry
+        final_carry = bool(final_bit_sum & 2)
+        return c, final_carry
     else:
         return c
+
+
+def binary_subtraction_1_complement(first_term: BasicRegister, second_term: BasicRegister) -> BasicRegister:
+    size_a = len(first_term)
+    size_b = len(second_term)
+
+    required_size = max(size_a, size_b)
+
+    a = first_term
+    b = second_term
+
+    if size_a != size_b:
+        a = a.adjusted_by_size(required_size)
+        b = b.adjusted_by_size(required_size)
+
+    b.reverse()
+
+    c: BasicRegister
+    final_carry: bool
+    c, final_carry = binary_sum(a, b, True)
+
+    if final_carry:
+        return binary_sum(c, BasicRegister([True]))
+    else:
+        c.reverse()
+        return c
+
+
+def binary_subtraction_2_complement(first_term: BasicRegister, second_term: BasicRegister) -> BasicRegister:
+    pass