Variable declaration using var in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of variable declaration with var and default value

What is the output of this Go program?

Go

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

A undefined

B nil

C 0

D 1

💡 Hint

Variables declared with var get a default zero value.

In Go, when you declare a variable with var but do not assign a value, it gets the zero value for its type. For int, the zero value is 0.

❓ Predict Output

intermediate

Output of multiple variable declaration using var

What will this Go program print?

Go

package main
import "fmt"
func main() {
    var a, b, c = 1, "hello", true
    fmt.Println(a, b, c)
}

A 1 0 true

B 1 hello true

C 0 hello false

D Compilation error

💡 Hint

var can declare multiple variables with initial values.

Variables a, b, c are declared with values 1, "hello", and true respectively, so printing them shows those values.

❓ Predict Output

advanced

Output of var declaration with explicit type and no initial value

What is the output of this Go program?

Go

package main
import "fmt"
func main() {
    var flag bool
    fmt.Println(flag)
}

A false

B true

C nil

D Compilation error

💡 Hint

Boolean variables default to false if not initialized.

The zero value for bool type in Go is false, so flag prints false.

❓ Predict Output

advanced

Output of var declaration with short variable declaration inside function

What will this Go program print?

Go

package main
import "fmt"
func main() {
    var x int = 10
    y := 20
    fmt.Println(x + y)
}

A 30

B 1020

C Compilation error

D 0

💡 Hint

The + operator adds integers.

x is 10 and y is 20, so x + y equals 30.

🧠 Conceptual

expert

Error caused by var declaration with conflicting types

What error will this Go code produce?

Go

package main
func main() {
    var x int = 5
    var x string = "hello"
}

A no error, compiles fine

B type mismatch error

C syntax error: missing semicolon

D cannot redeclare x

💡 Hint

You cannot declare two variables with the same name in the same scope.

The code tries to declare x twice in the same scope, which causes a redeclaration error.