Short variable declaration in Go - Step-by-Step Execution

Concept Flow - Short variable declaration

Start

↓

Use := to declare and assign

↓

Variable created with type inferred

↓

Variable ready to use

↓

End

The short variable declaration uses := to create and assign a variable in one step, with Go inferring the type automatically.

Execution Sample

Go

package main
import "fmt"
func main() {
  x := 10
  fmt.Println(x)
}

This code declares a variable x with value 10 using short declaration and prints it.

Execution Table

Step	Code Line	Action	Variable State	Output
1	x := 10	Declare x and assign 10	x = 10 (int)
2	fmt.Println(x)	Print value of x	x = 10 (int)	10
3	End	Program ends	x = 10 (int)

💡 Program ends after printing the value of x

Variable Tracker

Variable	Start	After 1	After 2	Final
x	undefined	10	10	10

Key Moments - 2 Insights

Why do we use := instead of = when declaring a variable?

The := operator both declares and assigns a variable in one step, as shown in execution_table step 1. Using = alone would require the variable to be declared first.

What type does the variable x have after declaration?

Go infers the type from the assigned value. In execution_table step 1, x is assigned 10, so its type is int.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of x after step 1?

A 10

B undefined

C 0

D nil

💡 Hint

Check the 'Variable State' column in row for step 1 in execution_table

At which step is the variable x printed?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

Look at the 'Code Line' and 'Action' columns in execution_table

If we replace := with = in line 1, what will happen?

A Variable x will be declared and assigned

B Compilation error because x is not declared

C x will be assigned zero value

D Program will print 0

💡 Hint

Recall that := declares and assigns, = only assigns to existing variables

Concept Snapshot

Short variable declaration uses := to declare and assign a variable in one step.
Go infers the variable type automatically from the assigned value.
Example: x := 10 declares x as int with value 10.
Use := only inside functions, not for package-level variables.
Trying to use = without prior declaration causes an error.

Full Transcript

This example shows how to use short variable declaration in Go. The := operator declares a variable and assigns a value at the same time. In the code, x := 10 creates an integer variable x with value 10. Then fmt.Println(x) prints the value 10. The execution table traces these steps clearly. The variable tracker shows x changes from undefined to 10 after declaration. Key moments clarify why := is needed and how Go infers types. The quiz tests understanding of variable state and declaration rules. This helps beginners see how short variable declaration works step-by-step.