diff --git a/2020-computer-science-igcse-prerelease-pseudocode.txt b/2020-computer-science-igcse-prerelease-pseudocode.txt
index bd4aacd..bef207c 100644
--- a/2020-computer-science-igcse-prerelease-pseudocode.txt
+++ b/2020-computer-science-igcse-prerelease-pseudocode.txt
@@ -1,4 +1,4 @@
-FUNCTION get_input( dict):
+FUNCTION get_input(dict):
    tmp <- None
    WHILE (not tmp):
        tmp <- input().upper().strip()
@@ -10,14 +10,14 @@ FUNCTION get_input( dict):
    RETURN tmp
 ENDFUNCTION
 
-FUNCTION print_details( dict):
+FUNCTION print_details(dict):
    FOR item in dict.keys():
        OUTPUT "%s: $%.2f, %s" % (item, dict[item][0], dict[item][1])
    ENDFOR
 ENDFUNCTION
 
   
-FUNCTION print_chosen( dict, item):
+FUNCTION print_chosen(dict, item):
    OUTPUT "%s: %s" % (item, dict[item][1])
    RETURN dict[item][0]
 ENDFUNCTION
@@ -45,19 +45,19 @@ run <- True
 devices <- 0
 WHILE run:
    OUTPUT "Choose an option:"
-   print_details( devices_dict)
-   device <- get_input( devices_dict)
+   print_details(devices_dict)
+   device <- get_input(devices_dict)
    devices += 1
    IF (device in phones_dict.keys()):
        OUTPUT "Choose an option:"
-       print_details( sims_dict)
-       sim_payg <- get_input( sims_dict)
+       print_details(sims_dict)
+       sim_payg <- get_input(sims_dict)
    ENDIF
    OUTPUT "Choose an option:"
-   print_details( case_dict)
-   case <- get_input( case_dict)
+   print_details(case_dict)
+   case <- get_input(case_dict)
    OUTPUT "Which charger(s) would you like? Enter the codes for those you want with a space between them, or enter nothing to choose neither"
-   print_details( charger_dict)
+   print_details(charger_dict)
    chargers <- input().upper().split(" ")
    FOR item in chargers:
        IF item not in charger_dict:
@@ -65,17 +65,17 @@ WHILE run:
        ENDIF
    ENDFOR
    IF (devices > 1):
-       total += 0.9 * print_chosen( devices_dict, device)
-       saving += 0.1 * print_chosen( devices_dict, device)
+       total += 0.9 * print_chosen(devices_dict, device)
+       saving += 0.1 * print_chosen(devices_dict, device)
    ELSE:
-       total += print_chosen( devices_dict, device)
+       total += print_chosen(devices_dict, device)
    ENDIF
    IF (device in phones_dict):
-       total += print_chosen( sims_dict, sim_payg)
+       total += print_chosen(sims_dict, sim_payg)
    ENDIF
-   total += print_chosen( case_dict, case)
+   total += print_chosen(case_dict, case)
    FOR charger in chargers:
-       total += print_chosen( charger_dict, charger)
+       total += print_chosen(charger_dict, charger)
    ENDFOR
    OUTPUT "Subtotal: $%.2f" % total
    run <- True IF (input("Would you like another device (y/n)?").lower().strip()[0] = "y") ELSE False
diff --git a/recursion-exercises.py b/recursion-exercises.py
new file mode 100644
index 0000000..03160da
--- /dev/null
+++ b/recursion-exercises.py
@@ -0,0 +1,40 @@
+# function to sum integers via recursion
+def total(numbers):
+	# if recursion not needed due to too few items
+	if len(numbers) == 1:
+		return numbers[0]
+	return numbers[0] + total(numbers[1:])
+
+# function to find if number is prime via recursion
+def prime(number, divisor = None):
+	# create initial divisor, only if it doesn't exist
+	if not divisor:
+		# divide by two because all factors are duplicated - searching through all numbers smaller than the given number would search all factor pairs twice
+		# floor divide because if it's not an integer, it's not a valid factor - so can be ignored
+		# if rounded up, the number's compliment will appear again later, in the reverse of the factor pair
+		divisor = number // 2
+	# number isn't a prime if less than two, or if it has a factor that's greater than one
+	if (number <= 1) or (divisor > 1 and number % divisor == 0):
+		return False
+	# all prime have been checked, and none are factors of the number
+	elif (divisor <= 1):
+		return True
+	else:
+		return prime(number, divisor - 1)
+
+# function for binary search via recursion
+def search(item, list):
+	# get middle index (-1 accounts for zero-based indexing)
+	midpoint = (len(list) + 1) // 2 - 1
+	# item found
+	if item == list[midpoint]:
+		return True
+	# all of list searched and item not found
+	elif (len(list) == 1):
+		return False
+	# item is larger than the middle item, so must be in the larger half of the list
+	elif item > list[midpoint]:
+		return search(item, list[midpoint + 1:])
+	# item is smaller than the middle item, so must be in the smaller half of the list
+	else:
+		return search(item, list[:midpoint])
\ No newline at end of file