Array declaration in Go - Step-by-Step Execution

Concept Flow - Array declaration

Start

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Declare array with size and type

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Memory allocated for fixed size

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Array elements initialized to zero values

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Array ready to use

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End

This flow shows how declaring an array in Go reserves fixed memory and initializes elements to zero values.

Execution Sample

Go

var arr [3]int
arr[0] = 10
arr[1] = 20
arr[2] = 30

Declare an integer array of size 3 and assign values to each element.

Execution Table

Step	Action	Array State	Explanation
1	Declare array var arr [3]int	[0 0 0]	Array of 3 ints created, all elements zero
2	Assign arr[0] = 10	[10 0 0]	First element set to 10
3	Assign arr[1] = 20	[10 20 0]	Second element set to 20
4	Assign arr[2] = 30	[10 20 30]	Third element set to 30
5	End	[10 20 30]	Array fully initialized with assigned values

💡 All array elements assigned, program ends

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
arr	undefined	[0 0 0]	[10 0 0]	[10 20 0]	[10 20 30]	[10 20 30]

Key Moments - 3 Insights

Why are all array elements zero after declaration?

In Go, arrays are initialized with zero values for their type automatically, as shown in execution_table step 1.

Can we assign values outside the declared size of the array?

No, arrays have fixed size. Trying to assign arr[3] would cause a runtime panic, as the array size is 3 (indices 0 to 2).

Is the array size changeable after declaration?

No, the size is fixed at declaration and cannot be changed later, as shown by the fixed array state in variable_tracker.

Visual Quiz - 3 Questions

Look at the execution_table, what is the array state after step 2?

A [0 10 0]

B [0 0 10]

C [10 0 0]

D [10 20 0]

💡 Hint

Check the 'Array State' column in execution_table row with Step 2.

At which step does the array become fully assigned with non-zero values?

A Step 2

B Step 4

C Step 3

D Step 1

💡 Hint

Look at the 'Array State' column in execution_table to see when all elements are non-zero.

If we declare var arr [5]int instead of [3]int, how would the initial array state change?

A [0 0 0 0 0]

B [0 0 0]

C [10 20 30 0 0]

D Array size would remain 3

💡 Hint

Refer to variable_tracker and concept_flow about array size and initialization.

Concept Snapshot

Array declaration in Go:
var arr [size]type
- Fixed size array
- Elements initialized to zero values
- Size cannot change after declaration
- Access elements by index arr[0], arr[1], ...

Full Transcript

In Go, declaring an array reserves fixed memory for a set number of elements of a specific type. The syntax is var arr [3]int which creates an array of 3 integers. All elements start with zero values automatically. You can assign values to each element by index, like arr[0] = 10. The array size is fixed and cannot be changed after declaration. Trying to access or assign outside the declared size causes an error. This example shows step-by-step how the array is created and updated.