Pointer declaration in Go - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a pointer to an integer variable.

Go

var p [1]int

Drag options to blanks, or click blank then click option'

A*

B&

C&&

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of * to declare a pointer type.

Using invalid symbols like && or #.

In Go, a pointer to a type is declared using the * symbol before the type.

2fill in blank

medium

Complete the code to assign the address of variable x to pointer p.

Go

p := [1]x

Drag options to blanks, or click blank then click option'

A&

B*

C&&

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Using * instead of & to get the address.

Using invalid symbols like && or #.

The address of a variable is obtained using the & operator in Go.

3fill in blank

hard

Fix the error in the pointer declaration to correctly declare a pointer to a string.

Go

var strPtr [1]string

Drag options to blanks, or click blank then click option'

A#

B&

C&&

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of * in type declaration.

Using invalid symbols like && or #.

The correct way to declare a pointer to a string is using *string.

4fill in blank

hard

Fill both blanks to declare a pointer to a float64 and assign it the address of variable f.

Go

var ptr [1]float64
ptr = [2]f

Drag options to blanks, or click blank then click option'

A*

B&

C#

D&&

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up * and & operators.

Using invalid symbols like # or &&.

Use * to declare a pointer type and & to get the address of a variable.

5fill in blank

hard

Fill all three blanks to declare a pointer to an int, assign it the address of n, and then dereference it to get the value.

Go

var p [1]int
p = [2]n
value := [3]p

Drag options to blanks, or click blank then click option'

A*

B&

Cp

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Using & instead of * for pointer declaration or dereferencing.

Using invalid symbols like #.

Declare pointer with *int, assign address with &n, and dereference with *p.

Practice

1. What does a pointer in Go store?

easy

A. The actual value of a variable

B. The memory address of a variable

C. The type of a variable

D. The size of a variable

Solution

1. Step 1: Understand what a pointer represents

   A pointer does not hold the value itself but the location where the value is stored in memory.

2. Step 2: Recall pointer definition in Go

   In Go, a pointer stores the address of a variable, not the variable's value directly.

3. Final Answer:

   The memory address of a variable -> Option B

4. Quick Check:

   Pointer = memory address [OK]

Hint: Pointers always hold addresses, not values [OK]

Common Mistakes:

• Thinking pointers store the actual value
• Confusing pointer with variable type
• Assuming pointer stores variable size

2. Which of the following is the correct way to declare a pointer to an int variable named num in Go?

easy

A. var p int = &num

B. var p *int = num

C. var p *int = &num

D. var p int = *num

Solution

1. Step 1: Understand pointer declaration syntax

   In Go, to declare a pointer to an int, use *int as the type.

2. Step 2: Assign the address of num to the pointer

   The address operator & gets the memory address of num, which can be assigned to the pointer.

3. Final Answer:

   var p *int = &num -> Option C

4. Quick Check:

   Pointer declaration uses *type and &variable [OK]

Hint: Pointer type uses * before type, assign with &variable [OK]

Common Mistakes:

• Forgetting the * in pointer type
• Assigning variable value instead of address
• Using *num instead of &num for assignment

3. What will be the output of this Go program?

package main
import "fmt"
func main() {
  x := 10
  p := &x
  *p = 20
  fmt.Println(x)
}

medium

A. 20

B. 10

C. Memory address of x

D. Compilation error

Solution

1. Step 1: Understand pointer assignment and dereferencing

   Variable p stores the address of x. Using *p = 20 changes the value at that address.

2. Step 2: Check the effect on x

   Since p points to x, changing *p changes x to 20.

3. Final Answer:

   20 -> Option A

4. Quick Check:

   Dereferencing pointer changes original variable [OK]

Hint: Changing *p changes the original variable [OK]

Common Mistakes:

• Thinking *p creates a new variable
• Expecting output to be address instead of value
• Confusing pointer declaration with dereferencing

4. Identify the error in this Go code snippet:

var a int = 5
var p *int = a
fmt.Println(*p)

medium

A. Cannot assign int to *int without & operator

B. Cannot print pointer value with * operator

C. Variable a must be a pointer

D. Missing import fmt

Solution

1. Step 1: Check pointer assignment rules

   Pointer variables must be assigned the address of a variable, not the variable's value.

2. Step 2: Identify missing & operator

   Assigning a directly to p is invalid; it should be p = &a.

3. Final Answer:

   Cannot assign int to *int without & operator -> Option A

4. Quick Check:

   Pointer assignment needs &variable [OK]

Hint: Use & to assign address to pointer variables [OK]

Common Mistakes:

• Assigning value instead of address to pointer
• Forgetting to import fmt for Println
• Thinking *p prints address instead of value

5. Given the code below, what will be the output?

package main
import "fmt"
func updateValue(p *int) {
  *p = *p + 5
}
func main() {
  val := 10
  updateValue(&val)
  fmt.Println(val)
}

hard

A. 10

B. Compilation error

C. Memory address of val

D. 15

Solution

1. Step 1: Understand function parameter as pointer

   The function updateValue takes a pointer to an int and modifies the value at that address.

2. Step 2: Trace the function call and modification

   Passing &val sends the address of val. Inside the function, *p = *p + 5 increases val by 5.

3. Step 3: Check final print output

   After the function call, val is updated to 15, so fmt.Println(val) prints 15.

4. Final Answer:

   15 -> Option D

5. Quick Check:

   Pointer parameter modifies original variable [OK]

Hint: Passing &variable lets function change original value [OK]

Common Mistakes:

• Passing value instead of address to function
• Expecting original variable unchanged
• Confusing pointer dereference syntax