Writing first Go program - Step-by-Step Execution

Concept Flow - Writing first Go program

Start program

↓

Import fmt package

↓

Define main function

↓

Execute fmt.Println("Hello, world!")

↓

Print output to screen

↓

Program ends

The program starts, imports the fmt package for printing, runs the main function, prints the message, then ends.

Execution Sample

Go

package main

import "fmt"

func main() {
    fmt.Println("Hello, world!")
}

This program prints 'Hello, world!' to the screen.

Execution Table

Step	Action	Evaluation	Result
1	Start program	N/A	Program begins execution
2	Import fmt package	N/A	fmt package loaded for printing
3	Define main function	N/A	main function ready to run
4	Call fmt.Println with "Hello, world!"	fmt.Println("Hello, world!")	Prints Hello, world! to screen
5	End main function	N/A	Program finishes

💡 Program ends after printing the message.

Variable Tracker

Variable	Start	After Step 4	Final
N/A	N/A	N/A	N/A

Key Moments - 3 Insights

Why do we need to import the fmt package?

The fmt package provides the Println function used to print text. Without importing it, the program cannot print anything. See step 2 in the execution table.

What is the main function for?

The main function is the starting point of the program where execution begins. The code inside main runs first. See step 3 and 4 in the execution table.

Why does the program end after printing?

After the main function finishes running, the program has no more instructions and stops. See step 5 and exit note.

Visual Quiz - 3 Questions

Look at the execution table, what happens at step 4?

A The program ends

B The program imports the fmt package

C The program prints 'Hello, world!' to the screen

D The main function is defined

💡 Hint

Check the 'Action' and 'Result' columns at step 4 in the execution table.

At which step does the program finish running?

A Step 5

B Step 3

C Step 2

D Step 1

💡 Hint

Look at the 'Step' and 'Result' columns to find when the program ends.

If we remove the import statement, what will happen?

A The program will print 'Hello, world!' anyway

B The program will fail because fmt.Println is undefined

C The program will run but print nothing

D The program will end immediately

💡 Hint

Refer to the key moment about why importing fmt is necessary.

Concept Snapshot

Go program starts with package main
Import fmt package to print
Define main() function as entry point
Use fmt.Println() to print text
Program runs main, prints, then ends

Full Transcript

This Go program starts by declaring package main, which is required for executable programs. It imports the fmt package to use its Println function for printing text. The main function is defined as the program's entry point. Inside main, fmt.Println("Hello, world!") prints the message to the screen. After printing, the program ends because main finishes execution.