Array limitations in Go - Step-by-Step Execution

Concept Flow - Array limitations

Declare array with fixed size

↓

Try to add more elements than size?

Yes→Error: cannot exceed size

No↓

Access elements by index

↓

Try to access index out of range?

Yes→Runtime panic: index out of range

No↓

Array size fixed, cannot resize

↓

END

Arrays have a fixed size set at declaration. You cannot add more elements than this size, and accessing outside the range causes errors.

Execution Sample

Go

package main
func main() {
  var arr [3]int
  arr[0] = 10
  arr[3] = 20
}

This code declares an array of size 3 and tries to assign a value to index 3, which is out of range.

Execution Table

Step	Action	Array State	Index Access	Result/Output
1	Declare array arr of size 3	[0, 0, 0]	N/A	Array created with default zeros
2	Assign arr[0] = 10	[10, 0, 0]	Index 0	Value 10 stored at index 0
3	Assign arr[3] = 20	Error	Index 3	Runtime panic: index out of range

💡 Execution stops due to runtime panic accessing index 3 which is outside array bounds

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
arr	N/A	[0, 0, 0]	[10, 0, 0]	Runtime panic - no change

Key Moments - 3 Insights

Why can't we add more elements than the declared size of an array?

Arrays in Go have a fixed size set at declaration, so trying to add beyond that size is not allowed and causes errors, as shown in step 3 of the execution_table.

What happens if we try to access an index outside the array range?

Accessing an index outside the array range causes a runtime panic (error) and stops the program, as seen in step 3 where arr[3] causes a panic.

Can we resize an array after it is declared?

No, arrays have a fixed size and cannot be resized. To have resizable collections, slices should be used instead.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of arr after step 2?

A [0, 0, 10]

B [10, 0, 0]

C [0, 10, 0]

D [10, 10, 10]

💡 Hint

Check the 'Array State' column in row for step 2 in execution_table

At which step does the program stop due to an error?

A Step 3

B Step 1

C Step 2

D Program does not stop

💡 Hint

Look at the 'Result/Output' column for each step in execution_table

If we try to assign arr[2] = 30 instead of arr[3], what would happen?

A Compile time error

B Runtime panic error

C Value 30 stored at index 2

D Array size increases

💡 Hint

Refer to variable_tracker and execution_table for valid index assignments

Concept Snapshot

Arrays have fixed size declared at creation.
Cannot add elements beyond this size.
Accessing out-of-range index causes runtime panic.
Arrays cannot be resized.
Use slices for flexible size collections.

Full Transcript

In Go, arrays have a fixed size set when you declare them. For example, var arr [3]int creates an array with exactly 3 elements. You can assign values to indexes 0, 1, and 2. Trying to assign or access index 3 causes a runtime panic because it is out of range. Arrays cannot grow or shrink after creation. If you need a flexible size, use slices instead. This example shows declaring an array, assigning a value to a valid index, and then trying to assign a value to an invalid index which causes the program to stop with an error.