Variable declaration using var in Go - Step-by-Step Execution

Concept Flow - Variable declaration using var

Start

↓

Declare variable with var

↓

Assign default zero value

↓

Use variable in code

↓

End

The program starts by declaring a variable using var, which assigns a default zero value. Then the variable can be used in the code.

Execution Sample

Go

package main
import "fmt"
var x int
func main() {
  fmt.Println(x)
}

Declares an integer variable x using var and prints its default value 0.

Execution Table

Step	Action	Variable	Value	Output
1	Declare variable x with var	x	0 (default int)
2	Enter main function	x	0
3	Print x	x	0	0
4	Program ends	x	0

💡 Program ends after printing the default value of x which is 0.

Variable Tracker

Variable	Start	After Declaration	After Print	Final
x	undefined	0	0	0

Key Moments - 2 Insights

Why does x have the value 0 even though we didn't assign anything?

In Go, when you declare a variable with var but don't assign a value, it automatically gets the zero value for its type. See execution_table step 1 where x is set to 0.

Can we use x before declaring it with var?

No, variables must be declared before use. The execution_table shows declaration happens first (step 1) before printing (step 3).

Visual Quiz - 3 Questions

Look at the execution table, what is the value of x right after declaration?

A undefined

B 1

C 0

D nil

💡 Hint

Check execution_table row 1 under Value column.

At which step does the program print the value of x?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look for the step with Action 'Print x' in execution_table.

If we change var x int to var x string, what would be the default value of x?

A "" (empty string)

B 0

C nil

D undefined

💡 Hint

Recall Go assigns zero value based on type; for string it's empty string.

Concept Snapshot

var declares a variable with a type.
If no value assigned, Go sets zero value by type.
Example: var x int sets x to 0.
Use variable after declaration.
Zero values: int=0, string="", bool=false.

Full Transcript

This example shows how to declare a variable in Go using var. When you write var x int, Go creates x as an integer variable and sets it to 0 automatically because no value was assigned. The program then prints x, showing 0. Variables must be declared before use. Different types have different zero values, like empty string for string type. This helps avoid errors from uninitialized variables.