Array length in Go - Step-by-Step Execution

Concept Flow - Array length

Declare array

↓

Array created with fixed size

↓

Use len(array) to get length

↓

Length returned as integer

↓

Use length in program

This flow shows how an array is declared with a fixed size, then the built-in len function returns its length as an integer.

Execution Sample

Go

package main
import "fmt"
func main() {
  arr := [5]int{1,2,3,4,5}
  fmt.Println(len(arr))
}

This code creates an array of 5 integers and prints its length using len.

Execution Table

Step	Action	Array Content	len(arr) Value	Output
1	Declare arr as [5]int{1,2,3,4,5}	[1 2 3 4 5]	N/A	N/A
2	Call len(arr)	[1 2 3 4 5]	5	N/A
3	Print length	[1 2 3 4 5]	5	5
4	Program ends	[1 2 3 4 5]	5	N/A

💡 Program ends after printing the length 5.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
arr	undefined	[1 2 3 4 5]	[1 2 3 4 5]	[1 2 3 4 5]
len(arr)	N/A	N/A	5	5

Key Moments - 2 Insights

Why does len(arr) return 5 even if we only use some elements?

len(arr) returns the fixed size of the array, not how many elements are 'used'. See execution_table step 2 where len(arr) is 5 regardless.

Can the length of an array change after declaration?

No, arrays have fixed length in Go. The length is set when declared, as shown in step 1.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of len(arr) at step 2?

A 0

B 5

C Undefined

D 1

💡 Hint

Check the 'len(arr) Value' column at step 2 in execution_table.

At which step is the array declared with its values?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look at the 'Action' column to find when arr is declared.

If the array was declared as [3]int{1,2,3}, what would len(arr) be at step 2?

A 3

B 5

C 0

D Undefined

💡 Hint

len returns the declared size of the array, see variable_tracker for len(arr) values.

Concept Snapshot

Array length in Go:
- Arrays have fixed size declared at creation.
- Use len(array) to get the size.
- Length is an int representing total elements.
- Length does NOT change during program.
- Example: arr := [5]int{...}; len(arr) == 5

Full Transcript

This example shows how to get the length of an array in Go. First, an array named arr is declared with 5 integers. The len function returns the fixed size of the array, which is 5. The program prints this length. Arrays in Go have fixed size, so len(arr) always returns the declared size, not how many elements are used. The execution table traces each step: declaration, calling len, printing, and program end. The variable tracker shows arr contents and len(arr) value. Key moments clarify common confusions about fixed size and length meaning. The quiz tests understanding of these steps and values.