أنواع البرمجيات مع أمثلة من الحياة اليومية

Written Explanation

The sorting question: where does it run?

To classify software, ask: on which computer do these instructions run, and how did they get there?

Remember from Module 1 that software runs as a process on some machine, managed by an operating system. Different kinds of software simply run on different machines or in different places.

Here is the overview. We will take each kind in turn.

Desktop software

Desktop software (also called a desktop application) is installed on and runs on a personal computer: a PC or a laptop. It uses that computer's CPU, RAM, and storage directly, and it is managed by the computer's operating system.

Examples: a word processor, a code editor, a video editor, a calculator program on your PC.

Key properties:

• It is installed once and then can be started from the computer.
• Much of it can work without an internet connection, though some do need one.
• It runs as a process on your machine, which is the idea from Module 1.

Mobile software

Mobile software (a mobile app) is software installed on a phone or tablet. It is much like desktop software, but built for a different kind of device: a touch screen, a battery to save, and sensors such as a camera, GPS receiver, and microphone.

Examples: a camera app, a messaging app, a ride-hailing app, a banking app.

Key properties:

• Usually installed from an app store, a service run by the maker of the phone's operating system.
• Can use phone hardware such as the camera or GPS, with the user's permission.
• Many mobile apps need a connection to work fully. A ride app, for instance, needs to talk to other computers to find drivers.

A mobile app is in some ways only the "dining room" of a bigger product: the part you hold. We will return to that.

Web frontend

Now we come to the web. A website is shown inside a browser (such as Chrome, Firefox, Safari, or Edge). The part that runs in your browser is called the web frontend, or client side.

When you open a web page, your browser downloads files from a computer somewhere else. These typically include text and structure, pictures, styling (how it looks), and often small programs written in a language called JavaScript. The browser then shows the page and runs those programs on your own computer. MDN, the web documentation from Mozilla, describes this split: code that runs in the browser is client-side, and code that runs on a server is server-side.

Key properties:

• Nothing is installed: you just visit an address.
• It runs inside the browser's controlled space, with limited access to your computer.
• It is what you see and click: the page, the menus, the buttons.

Important: the web frontend is the visible part of a website. It is not the whole website, and it is certainly not the backend.

Backend software

Backend software runs on a server: a computer that is set up to answer requests from other computers. Servers are usually kept in data centers or rented from a cloud company, and their screens are rarely used. You never see this software directly.

The backend does the work that should not happen on your device:

• Stores data that must be kept permanently and shared (accounts, orders, messages).
• Applies the rules (checks a password, calculates the price, decides who may see what).
• Answers requests from frontends and apps.

Example: when you place an order in a food app, the order is sent from your phone to a backend. The backend checks it, saves it, and replies "order received". Your phone only displays the reply.

Why not do all of this on your own phone or in your own browser? Three reasons:

1. Shared data. Many users need to see the same data. A restaurant needs to see your order, which only exists on your phone otherwise.
2. Trust. Anything on your device can be changed by you. Rules such as prices and permissions must be enforced somewhere that users cannot tamper with.
3. Always on. Your phone sleeps and loses signal. A server is meant to be available all the time. The next lesson goes deep into this.

Embedded software

Embedded software lives inside a device that is not usually thought of as "a computer". The device contains a small computer (a processor, memory, and input and output parts) dedicated to a single job. The software that runs on it is often called firmware.

Examples: the controller of a washing machine, a microwave oven, a digital thermometer, a car's anti-lock braking system, the remote of your TV.

Key properties:

• It is shipped with the device. You do not install it like an app, and often you cannot see it.
• It does one specific job and often has limited memory and processing power.
• It talks directly to the hardware: motors, buttons, sensors, displays.

When you press "Start" on a washing machine, embedded software reads the button, turns on the motor, watches the water level, and stops at the right time.

One product, many kinds

Real products combine kinds. Take a food-ordering service:

• A mobile app for customers.
• A web frontend: the website of the same service, in a browser.
• A backend that holds restaurants, menus, and orders, used by both the app and the website.
• Perhaps embedded software in a tablet or printer in the restaurant that shows new orders.

All of these are separate pieces of software running in different places. They cooperate by sending messages to each other, and the backend is the shared center.

   Phone app ----\
                   >----  Backend (server)  ---- stores data, applies rules
   Website   ----/
   (browser)

This is why "a website" and "its backend" are not the same thing. The website you see in the browser is a frontend. The backend is a separate piece that you cannot see in the browser, which both the website and the app depend on.

How to decide: three questions

When you meet a new piece of software, ask in order:

1. Is it built into a device and shipped with it? If yes, it is likely embedded.
2. Does it run on my own device, which I installed, or in my browser? If installed on a PC, desktop. If installed on a phone or tablet, mobile. If it runs in the browser after I open a page, web frontend.
3. Does it run on a server that I do not see, answering requests? Then it is backend.

Gray cases

Boundaries are not always sharp. Be ready for these:

• A smart TV menu. The menu software runs on the TV itself, built into the device, so it is embedded. Streaming apps on the TV may also exist, installed like mobile apps, and the movies they show come from a backend.
• A smartwatch. Its basic functions are embedded, and apps you install behave like mobile apps. It also usually needs a backend.
• A web app installed on a phone. Some websites can be saved to a phone's home screen, but the code still comes from a web page. We keep it simple and call it a web frontend unless it is a normal installed mobile app.
• A desktop app that is really a web page inside a window. From the user's side it is installed and starts on its own, so we count it as desktop, though a web-style frontend runs inside it. When the exact answer is unclear, say which part is which instead of forcing one label.

The five kinds are tools for thinking. In an assessment, pick the kind that answers "where does it run?" for the main piece of software in question.