diff --git a/Grade 10/ICS4U1/Class_1.md b/Grade 10/ICS4U1/Class_1.md
index e9b331b..3233c09 100644
--- a/Grade 10/ICS4U1/Class_1.md	
+++ b/Grade 10/ICS4U1/Class_1.md	
@@ -1,4 +1,4 @@
-# Class 1 notes
+# Class 1 Notes
 
 # Array Review
 
@@ -8,6 +8,8 @@
 - Each **cell** holds a value
 - All the values are the same **type**
 - It can store all kinds of data, `int`, `double`, `object`, etc, the type stored can be primitive (`int`) or reference (`object`)
+- Once an array has been created, the number of cells **cannot** be changed.
+
 
 ## Example
 
@@ -36,3 +38,59 @@
 </tr>
 </table>
 
+- The array name is `bowlingScores`, you can access specific value at a specific index: eg. `bowlingScores[3]` = 138.
+- If there are $`n`$ cells in the array the indexes will be from $`0`$ to $`n-1`$, arrays are 0-index based.
+- If we are acessing a value out of the range of the array, such as `bowlingScores[8]`, then we get an `ArrayOutOfBounds Error`.
+
+## Initializing Arrays
+- General syntax to declare an array:
+
+```java
+final int MAX = 8;
+int [] bowlingScores= new int[MAX];
+bowlingScores[0] = 180; // initializing
+bowlingScores[1] = 120; // initializing
+...
+```
+- To intialize all the values at once, we can do:
+
+```java
+int[] luckyNumbers = {2, 3, 10, 4, 17, 21}; // known values
+```
+
+## Summing Values In An Array
+
+### In Main 
+```java
+int sum; // declare an accumulator
+sum = 0;
+for(int i=0; i<MAX i++) {
+    sum = sum + list[i]; // sum += list[i];
+}
+System.out.println("The sum of all values in the array in the array is " + sum);
+```
+
+### As A Method
+```java
+public int findSum(int [] list) {
+    int sum; // declare an accumulator
+    sum = 0;
+    for(int i=0; i<MAX i++) {
+        sum = sum + list[i]; // sum += list[i];
+    }
+    System.out.println("The sum of all values in the array in the array is " + sum);
+}
+```
+
+## Method That Returns An Array
+
+```java
+public int[] getNewList() {
+    int [] list = new int[10];
+    for(int i=0; i<10; i++) {
+        list[i] = i;
+    }
+    return list;
+}
+```
+