The apps on your phone are programs too — and you can build one without typing code, using a visual app builder. This chapter introduces mobile apps and block-based app development.
1Types of apps & their uses
A mobile application (app) is software made to run on phones/tablets. Three kinds:
| Type | What it is | Example |
|---|---|---|
| Native | Built for one platform (Android or iOS); fast, full device access | WhatsApp installed from the store |
| Web app | Runs in the browser; no install needed | A website that works like an app |
| Hybrid | A mix — one app that works on many platforms | Many store apps built with web tech |
Apps have huge social impact across categories: Educational (Vidaara), E-Commerce (shopping), Social (messaging), and Utilities (calculator, maps).
- An app is software for phones/tablets; types are native (one platform), web (in the browser), and hybrid (cross-platform).
- Native apps are fast with full device access; web apps need no install.
- App categories: educational, e-commerce, social and utilities.
2Visual app builders & UI design
Tools like MIT App Inventor and other blockly frameworks let you build apps by dragging blocks — no text coding. They have two sides:
| Part | You use it to |
|---|---|
| Designer | Lay out the screen (the user interface) |
| Blocks editor | Add the logic (what happens when you tap) |
UI components
You drag components onto the screen to design the user interface (UI):
- Button — something to tap.
- Label — text to display.
- Image — a picture.
- Text input — a box for the user to type.
- MIT App Inventor / blockly tools build apps by dragging blocks — no typing code.
- The Designer lays out the screen (UI); the Blocks editor adds the logic.
- UI components: buttons, labels, images and text inputs.
3Logic blocks & screens
In the Blocks editor you join puzzle-piece blocks to say what happens. The most common is reacting to a tap:
when Button1.Click do set Label1.Text to "Hello!"
This is an event ("when Button1 is clicked") with an action ("set the label's text"). Apps can also have several screens, and a block can navigate from one screen to another when a button is tapped.
- Logic is built by joining blocks: an event (when Button.Click) triggers an action (set Label.Text).
- Apps can have multiple screens; a block can navigate between them on a tap.
- It's the same 'when X happens, do Y' logic as code — just drawn as blocks.
★ Practical: plan a simple app
On paper (or in MIT App Inventor if available), plan a 'Greeting' app:
- List the UI components on the screen (a text input, a button, a label).
- Write the logic in plain words: when the button is clicked, set the label to a greeting using the typed name.
- Classify your app as native, web or hybrid and say why.
- Suggest a second screen the app could navigate to.
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