diff --git a/13_functions/func.v b/13_functions/func.v
new file mode 100644
index 0000000..fb242bd
--- /dev/null
+++ b/13_functions/func.v
@@ -0,0 +1,30 @@
+struct User{
+	name string
+mut:
+	is_registered bool
+}
+
+fn (mut user User) register(){
+	user.is_registered = true
+}
+
+
+fn multiply_by_2(mut arr[] int){
+	for i in 0..arr.len{
+		arr[i] *= 2
+	}
+}
+
+pub fn main(){
+	
+	mut user := User{}
+	
+	println(user.is_registered)
+	user.register()
+	println(user.is_registered)
+
+	mut nums := [1,2,3]
+	multiply_by_2(mut nums)
+	println(nums)
+	
+}
\ No newline at end of file
diff --git a/13_functions/variable_number.v b/13_functions/variable_number.v
new file mode 100644
index 0000000..4314fe1
--- /dev/null
+++ b/13_functions/variable_number.v
@@ -0,0 +1,24 @@
+fn sum(a ...int) int{
+
+	mut total := 0
+
+	for x in a{
+		total += x
+	}
+
+	return total
+}
+
+pub fn main(){
+	println(sum())
+	println(sum(2,1))
+	println(sum(2,3,5,3))
+	println(sum(1))
+
+	a := [2,3,4]
+	println(sum(...a))
+
+	b := [4,5,6]
+	println(sum(...b))
+	
+}
\ No newline at end of file