Basic data types in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an int in Go?

An int is a basic data type in Go used to store whole numbers without decimals, like 1, 42, or -7.

beginner

What does the float64 type represent?

float64 is a data type for numbers with decimals, like 3.14 or -0.001. It uses 64 bits to store the value.

beginner

What is the string type used for in Go?

string stores text, like words or sentences, for example "hello" or "Go programming".

beginner

What is a bool type?

bool holds a value that is either true or false. It is used for yes/no or on/off decisions.

beginner

How do you declare a variable of type int in Go?

You can declare an int variable like this: var age int = 30. This creates a variable named age that holds the number 30.

Which Go data type would you use to store the number 42?

A string

B int

C bool

D float64

The number 42 is a whole number, so the int type is the best choice.

What value can a bool type hold?

A true or false

B Text strings

C Any number

D Decimal numbers

A bool type can only be true or false.

Which type is best for storing the text "hello"?

A float64

B int

C bool

D string

Text like "hello" is stored in a string type.

What is the difference between int and float64?

A int stores true/false, float64 stores numbers

B int stores text, float64 stores numbers

C int stores whole numbers, float64 stores decimal numbers

D int stores decimal numbers, float64 stores whole numbers

int is for whole numbers, float64 is for numbers with decimals.

How do you declare a variable named 'score' with value 100 as an int?

A var score int = 100

B score := "100"

C var score string = 100

D score = 100.0

The correct way is 'var score int = 100' to declare an int variable.

Explain the main basic data types in Go and give an example of each.

Think about numbers, text, and true/false values.

How do you declare and assign a variable of type string in Go?

Use 'var' and '=' to create the variable.

Practice

1. Which Go data type is used to store true or false values?

easy

A. float64

B. int

C. string

D. bool

Solution

1. Step 1: Understand the data types

   In Go, bool is used for true/false values, int for whole numbers, string for text, and float64 for decimals.

2. Step 2: Match the type to true/false

   Since true/false are boolean values, the correct type is bool.

3. Final Answer:

   bool -> Option D

4. Quick Check:

   Boolean type = bool [OK]

Hint: True/false values always use bool type in Go [OK]

Common Mistakes:

• Choosing int for true/false
• Using string for boolean values
• Confusing float64 with bool

2. Which of the following is the correct way to declare an integer variable named age in Go?

easy

A. int age

B. var age int

C. age := int

D. var int age

Solution

1. Step 1: Recall Go variable declaration syntax

   In Go, variables are declared with var followed by the name and then the type.

2. Step 2: Check each option

   var age int matches this syntax: var age int. Others do not follow Go syntax.

3. Final Answer:

   var age int -> Option B

4. Quick Check:

   Variable declaration = var name type [OK]

Hint: Use 'var name type' to declare variables in Go [OK]

Common Mistakes:

• Writing type before variable name
• Using := without initialization
• Mixing order of var and type

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

package main
import "fmt"
var x int = 10
var y float64 = 5.5
var z string = "Go"
func main() {
	fmt.Println(x, y, z)
}

medium

A. 10 5.5 Go

B. 10 5 Go

C. 10 5.5 "Go"

D. Error: cannot print variables

Solution

1. Step 1: Understand variable values

   Variable x is 10 (int), y is 5.5 (float64), and z is "Go" (string).

2. Step 2: Check fmt.Println output

   fmt.Println prints values separated by spaces without quotes for strings.

3. Final Answer:

   10 5.5 Go -> Option A

4. Quick Check:

   Print values as is, strings without quotes [OK]

Hint: fmt.Println prints strings without quotes by default [OK]

Common Mistakes:

• Expecting quotes around strings
• Confusing float64 with int
• Thinking fmt.Println causes error

4. Find the error in this Go code snippet:

var name string = 123
fmt.Println(name)

medium

A. fmt.Println requires parentheses

B. Missing semicolon after declaration

C. Cannot assign int to string variable

D. Variable name is a reserved keyword

Solution

1. Step 1: Check variable assignment types

   The variable name is declared as string but assigned the integer 123, which is a type mismatch.

2. Step 2: Verify other syntax

   Semicolons are optional in Go, fmt.Println is correctly used, and name is not a reserved keyword.

3. Final Answer:

   Cannot assign int to string variable -> Option C

4. Quick Check:

   Type mismatch error = assigning int to string [OK]

Hint: Match variable type and assigned value type exactly [OK]

Common Mistakes:

• Assigning wrong type value
• Thinking semicolon is mandatory
• Confusing reserved keywords

5. You want to store a person's age, height in meters, name, and if they are a student. Which Go variable declarations are correct?

hard

A. var age int
var height float64
var name string
var isStudent bool

B. var age float64
var height int
var name bool
var isStudent string

C. var age string
var height string
var name int
var isStudent int

D. var age bool
var height bool
var name float64
var isStudent int

Solution

1. Step 1: Match data types to real-world data

   Age is a whole number, so int. Height can have decimals, so float64. Name is text, so string. Student status is true/false, so bool.

2. Step 2: Check each option

   var age int var height float64 var name string var isStudent bool matches these types correctly. Others assign wrong types to variables.

3. Final Answer:

   var age int var height float64 var name string var isStudent bool -> Option A

4. Quick Check:

   Correct types for data = int, float64, string, bool [OK]

Hint: Use int for whole numbers, float64 for decimals, string for text, bool for true/false [OK]

Common Mistakes:

• Mixing int and float64
• Using bool for text
• Assigning string to boolean