Array indexing and access in C Sharp (C#) - Step-by-Step Execution

Concept Flow - Array indexing and access

Create array with elements

↓

Access element at index i

↓

Retrieve value stored at index i

↓

Use value (print, assign, etc.)

↓

End or repeat for other indices

This flow shows how an array is created, then an element is accessed by its index to retrieve and use its value.

Execution Sample

C Sharp (C#)

int[] numbers = {10, 20, 30, 40};
int value = numbers[2];
Console.WriteLine(value);

This code creates an array of integers, accesses the element at index 2, and prints it.

Execution Table

Step	Action	Index Accessed	Value Retrieved	Output
1	Create array 'numbers'	-	-	-
2	Access element at index 2	2	30	-
3	Assign value to variable 'value'	-	30	-
4	Print 'value'	-	30	30
5	End	-	-	-

💡 Program ends after printing the value at index 2.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
numbers	null	{10, 20, 30, 40}	{10, 20, 30, 40}	{10, 20, 30, 40}
value	undefined	undefined	30	30

Key Moments - 3 Insights

Why does accessing numbers[2] give 30 and not 20 or 40?

Array indexing starts at 0, so numbers[0] is 10, numbers[1] is 20, and numbers[2] is 30 as shown in step 2 of the execution table.

What happens if we try to access an index outside the array, like numbers[4]?

Accessing an index outside the array bounds causes a runtime error (IndexOutOfRangeException), because the array only has indices 0 to 3.

Is the value copied or referenced when we assign numbers[2] to 'value'?

For value types like int, the value is copied. So 'value' holds its own copy of 30, independent of the array.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'value' after step 3?

A 30

B 20

C undefined

D 40

💡 Hint

Check the 'Value Retrieved' column at step 3 in the execution table.

At which step is the array 'numbers' created?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Action' column in the execution table for array creation.

If we change the index accessed from 2 to 1, what value would be retrieved?

A 10

B 20

C 30

D 40

💡 Hint

Refer to the array contents in the variable tracker and the indexing rule explained in key moments.

Concept Snapshot

Array indexing starts at 0.
Access elements using array[index].
Index must be within 0 to length-1.
Access returns the value stored at that position.
Out-of-range index causes error.
Value types are copied on access.

Full Transcript

This lesson shows how arrays in C# store multiple values and how to access them using an index starting at zero. We create an array 'numbers' with four integers. Accessing numbers[2] retrieves the third element, which is 30. This value is assigned to a variable 'value' and printed. The execution table tracks each step, showing the array creation, index accessed, value retrieved, and output. Key points include understanding zero-based indexing, the importance of staying within array bounds, and that value types like int are copied when accessed. The visual quiz tests understanding of these steps and indexing rules.