← Hashito System Home ToolsBlog日本語
FREE
Tall, high-resolution PNG posters that explain everyday technology in a simple, friendly way. Print and use them freely for classroom display, lessons, projects, or learning at home. No sign-up required.
📝 Note: the posters themselves are written in Japanese (designed for Japanese elementary and middle school students).
Learning poster explaining QR code settings for students (in Japanese)
QR Code

QR Code Settings

Illustrates how QR codes work — version, error-correction level, and masking — and the trade-off "more robust, but larger."

Learning poster explaining barcode types and settings for students (in Japanese)
Barcode

Barcode Basics

Covers barcode types (JAN/EAN-13, CODE128, CODE39), how a 13-digit JAN works, and tips for clean, scannable codes.

Learning poster explaining IP address and subnet mask for students (in Japanese)
IP Address

IP Address Basics

IP = address, subnet mask = the town boundary. Explains the "/24" notation, DHCP, the gateway, and what each part does.

Learning poster explaining the role and history of HTML (in Japanese)
HTML

HTML Basics

HTML builds the "skeleton" of a web page. Covers tag structure, semantics, and its history since 1991.

Learning poster explaining the role and history of CSS (in Japanese)
CSS

CSS Basics

CSS controls the "look" of a web page. Covers selectors, responsive design, and its history since 1996.

Learning poster explaining the role and history of JavaScript (in Japanese)
JavaScript

JavaScript Basics

JavaScript gives a web page its "behavior." Its role, what it can do, and its history since 1995, in one page.

Learning poster explaining how a web page is displayed (in Japanese)
How the web works

How a Page is Displayed

From entering a URL to seeing the page: the technical flow of DNS → connect → fetch → render, illustrated.

Learning poster explaining common server attacks and defenses (in Japanese)
Security

Server Attacks & Defense

How common attacks work — DDoS, SQL injection, XSS and more — and how to defend against them, from a defender's view.

Learning poster explaining vulnerabilities and CVE management (in Japanese)
Security

Vulnerabilities & CVE

What software vulnerabilities are. CVE IDs, CVSS, and the flow from discovery to fix and disclosure, illustrated.

Learning poster explaining open-source software development and history (in Japanese)
Development

Open Source (OSS) Basics

What OSS is, the GitHub development flow, everyday examples, and its history from GNU and Linux, in one page.

A learning poster explaining binary and hexadecimal for kids
Computer Science

How Binary & Hex Work

How 0s and 1s represent numbers, the link between binary, hex and decimal, and conversions like FF = 255.

A learning poster explaining hash functions for kids
Security

How Hash Functions Work

A one-way 'fingerprint' of data: how it differs from encryption, and how it is used for tamper detection and storing passwords.

A learning poster explaining color codes and the RGB primaries for kids
Web

Color Codes & RGB

Screen colors come from red, green and blue light: 0-255 strengths, HEX like #FF0000, and how RGB relates to HSL.

A learning poster explaining how to make a strong password, for kids
Security

How to Make a Strong Password

A password is your personal secret. The best protection is to make it long and never reuse it across sites.

A learning poster explaining Base64 for kids
Encoding

What Is Base64?

Base64 turns data such as images into text made only of letters, digits and symbols. It is not encryption.

A learning poster explaining JSON for kids
Data Formats

What Is JSON?

JSON is a human-readable format often used when computers exchange data.

A learning poster explaining UUIDs for kids
Identifiers

What Is a UUID?

A UUID is a long number that almost never collides, even when many devices create their own.

A learning poster explaining URL encoding for kids
Web

How URL Encoding Works

URLs allow only certain characters. URL encoding replaces the others with '%' plus a number so they travel safely.

A learning poster explaining Unix time for kids
Date & Time

Computer Time

Computers count time as the number of seconds since January 1, 1970. That is Unix time.

A learning poster explaining diff for kids
Algorithms

How Diff Works

Diff finds the differences between two texts: it lines up what is the same, then shows what was added or removed.

A learning poster explaining JWT for kids
Authentication

What Is a JWT?

A JWT is a 'pass' that shows you are really you after logging in. It has three parts.

A learning poster explaining HTML escaping and XSS for kids
Security

HTML Escaping and XSS

Showing user input as-is can let bad code run (XSS). We prevent it by converting special characters.

A learning poster explaining naming conventions for kids
Coding

Naming Conventions

In programming, names follow styles. Keeping them consistent makes code easier to read and reduces mistakes.

A learning poster explaining regular expressions for kids
Coding

What Are Regular Expressions?

A regular expression describes a pattern of characters - like 'digits only' or 'an email shape' - so you can find it.

A learning poster explaining CSV and JSON for kids
Data Formats

CSV and JSON

CSV and JSON are two popular ways to store and exchange table-like data, each good at different things.

A learning poster explaining character codes and UTF-8 for kids
Text & Encoding

Character Codes and UTF-8

Computers store characters as numbers too. Unicode and UTF-8 can represent characters from all over the world.

A learning poster explaining placeholder text for kids
Design

What Is Placeholder Text?

Placeholder text is meaningless 'dummy' text used to check how a design looks. The classic one is Lorem ipsum.

Usage