Output using fmt.Println in Go - Step-by-Step Execution

Concept Flow - Output using fmt.Println

Start program

↓

Call fmt.Println

↓

Evaluate arguments

↓

Print output to console

↓

Move to next line

↓

Program ends

The program starts, calls fmt.Println to print values, outputs them to the console, then moves to the next line and ends.

Execution Sample

Go

package main
import "fmt"
func main() {
    fmt.Println("Hello, Go!")
}

This code prints the text "Hello, Go!" to the console using fmt.Println.

Execution Table

Step	Action	Evaluation	Output
1	Start program	N/A
2	Call fmt.Println with argument "Hello, Go!"	Argument evaluated as string "Hello, Go!"
3	Print output to console	Prints "Hello, Go!"	Hello, Go!
4	Move to next line	Newline added after output
5	Program ends	No more instructions

💡 Program ends after printing output and moving to next line.

Variable Tracker

Variable	Start	After fmt.Println	Final
N/A	N/A	N/A	N/A

Key Moments - 2 Insights

Why does fmt.Println add a new line after printing?

fmt.Println always adds a newline after printing, so the next output starts on a new line. See execution_table step 4.

What happens if we pass multiple arguments to fmt.Println?

fmt.Println prints all arguments separated by spaces, then adds a newline. This is shown in step 2 where arguments are evaluated.

Visual Quiz - 3 Questions

Look at the execution table, what is printed at step 3?

A fmt.Println function itself

B "Hello, Go!"

C No output

D A blank line

💡 Hint

Check the Output column at step 3 in the execution_table.

At which step does the program add a new line after printing?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the Action and Evaluation columns for step 4 in the execution_table.

If we add fmt.Println("Hi", "there"), how would the output change?

A Prints "Hithere" without space

B Prints only "Hi"

C Prints "Hi there" with a space and newline

D Causes an error

💡 Hint

Recall key_moments about multiple arguments and step 2 evaluation.

Concept Snapshot

fmt.Println prints values to the console followed by a newline.
Syntax: fmt.Println(value1, value2, ...)
Prints all arguments separated by spaces.
Always moves to next line after printing.
Used for simple output in Go programs.

Full Transcript

This example shows how Go's fmt.Println function outputs text to the console. The program starts and calls fmt.Println with the string "Hello, Go!". The argument is evaluated and printed. fmt.Println automatically adds a newline after printing, so the cursor moves to the next line. Finally, the program ends. This trace helps beginners see each step from calling the function to output appearing on screen.

Practice

1. What does the fmt.Println function do in Go?

easy

A. Creates a new package

B. Reads input from the user

C. Declares a new variable

D. Prints text or values to the screen with a new line

Solution

1. Step 1: Understand the purpose of fmt.Println

   The function fmt.Println is used to display output on the screen, automatically adding a new line after the output.

2. Step 2: Differentiate from other functions

   It does not read input, declare variables, or create packages; it only prints output.

3. Final Answer:

   Prints text or values to the screen with a new line -> Option D

4. Quick Check:

   fmt.Println prints output with newline [OK]

Hint: Remember: println means print with a new line [OK]

Common Mistakes:

• Confusing fmt.Println with input functions
• Thinking it declares variables
• Assuming it creates packages

2. Which of the following is the correct way to print "Hello, Go!" using fmt.Println?

easy

A. fmt.Println("Hello, Go!")

B. fmt.Println('Hello, Go!')

C. fmt.Println(Hello, Go!)

D. fmt.Println(Hello Go)

Solution

1. Step 1: Check string syntax in Go

   Strings must be enclosed in double quotes " ". Single quotes ' ' are for single characters.

2. Step 2: Validate the options

   fmt.Println("Hello, Go!") uses double quotes correctly. Options A, B, and C either use single quotes or no quotes, which causes errors.

3. Final Answer:

   fmt.Println("Hello, Go!") -> Option A

4. Quick Check:

   Strings need double quotes in fmt.Println [OK]

Hint: Use double quotes for strings in fmt.Println [OK]

Common Mistakes:

• Using single quotes for strings
• Omitting quotes around text
• Forgetting commas inside print

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

package main
import "fmt"
func main() {
    fmt.Println("Go", "is", "fun")
}

medium

A. Go is fun

B. Goisfun

C. "Go is fun"

D. Go, is, fun

Solution

1. Step 1: Understand fmt.Println with multiple arguments

   When multiple values are separated by commas, fmt.Println prints them separated by spaces automatically.

2. Step 2: Analyze the output

   The output will be the words separated by spaces: Go is fun, followed by a new line.

3. Final Answer:

   Go is fun -> Option A

4. Quick Check:

   fmt.Println adds spaces between arguments [OK]

Hint: Multiple arguments print with spaces automatically [OK]

Common Mistakes:

• Expecting no spaces between words
• Thinking commas print literally
• Confusing output with quotes

4. Find the error in this Go code snippet:

package main
import "fmt"
func main() {
    fmt.Println("Hello" + "World")
}

medium

A. Syntax error due to missing comma

B. Runtime error because + can't join strings

C. No error, it prints HelloWorld

D. fmt.Println requires parentheses

Solution

1. Step 1: Check string concatenation in Go

   Using + between strings concatenates them without spaces.

2. Step 2: Verify fmt.Println usage

   fmt.Println can print the concatenated string without error.

3. Final Answer:

   No error, it prints HelloWorld -> Option C

4. Quick Check:

   String + concatenates; fmt.Println prints result [OK]

Hint: String + joins text; no comma needed inside fmt.Println [OK]

Common Mistakes:

• Thinking + causes syntax error in print
• Expecting space between Hello and World
• Confusing + with comma separator

5. You want to print the numbers 1, 2, and 3 on the same line separated by spaces using fmt.Println. Which code snippet achieves this correctly?

hard

A. fmt.Println(1 2 3)

B. fmt.Println("1", "2", "3")

C. fmt.Println("1" "2" "3")

D. fmt.Println(1 + 2 + 3)

Solution

1. Step 1: Understand printing multiple values

   Using commas in fmt.Println prints each argument separated by spaces automatically.

2. Step 2: Analyze each option

   fmt.Println(1 2 3) causes syntax error (missing commas or operators).
   fmt.Println("1" "2" "3") concatenates adjacent strings to "123" without spaces.
   fmt.Println("1", "2", "3") prints 1 2 3 with spaces.
   fmt.Println(1 + 2 + 3) prints 6.

3. Step 3: Choose the best for printing numbers as strings separated by spaces

   fmt.Println("1", "2", "3") prints the numbers as strings separated by spaces, exactly as requested.

4. Final Answer:

   fmt.Println("1", "2", "3") -> Option B

5. Quick Check:

   Separate strings with commas to print spaced values [OK]

Hint: Use commas to separate values for spaced output [OK]

Common Mistakes:

• Using + to join numbers (adds them instead)
• Printing a single string instead of separate values
• Confusing string and integer printing