A library (ライブラリ) bundles frequently used processing into components such as functions so that other programs can call and reuse them.
Tasks like formatting strings or calculating dates do not have to be written from scratch each time, because you can call a ready-made component instead. Components that many developers have already used cut development effort and help keep quality consistent. What defines how to call a library's components is the API, covered next.
AnalogyIt is like using store-bought stock powder instead of making soup stock from scratch every time you cook.
How to rememberIn English, a library is a collection of books. You borrow the processing you need, just as you borrow a book.
Exam points
Mix-upA plug-in (プラグイン) is an add-on inserted into a finished application afterwards to add features, so it is used differently from a library (ライブラリ) that developers call from their own code.
An API (Application Programming Interface) is an agreed way of calling that lets other programs use a piece of software's functions.
Calling program
API (agreed way of calling)
Software providing the function
The caller makes a request using the specified names and way of passing values, and gets the result without knowing the internal workings. The provider can keep its internals hidden and expose only the functions needed, and as long as the agreement stays the same, rebuilding the internals does not affect the caller.
AnalogyIt is like a restaurant order slip. Order in the set format and the dish arrives, even though you do not know how the kitchen makes it.
How to rememberThe final I stands for Interface, the boundary where two things meet: an agreement placed at the boundary between programs.
Exam points
Mix-upAn API is the agreement for calling functions, whereas a library (ライブラリ) is the set of components that hold the processing being called, so the two refer to different things.
A Web API (WebAPI) is an API published so that the functions and data of a service on a network can be called over web communication such as HTTP.
App sends a request
Web API receives it
Service processes it
Result data is returned
The result comes back to the app as data, and the app uses it on screen or elsewhere.
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The service processes the request it receives and returns the result as data. The calling app can use the other service's functions without keeping components on hand, so an app can show, for example, weather forecasts or exchange rates.
AnalogyIt is like phoning an inquiry desk and getting an answer. You cannot see how the company works inside, but asking in the expected way gets you a reply.
How to rememberWeb + API: an ordinary API call that rides on web communication to reach a distant service.
Exam points
ExamA mashup (マッシュアップ) is a method of building a new service by pulling in the functions and data of several published services through Web APIs and similar means.
Low-code (ローコード) is a development method that builds apps mainly by placing and configuring components on screen, writing a small amount of code only where it is needed.
Most screens and process flows can be made by combining ready-made components, so an app takes shape faster than when a program is written from scratch. Processing that the components cannot express can be covered by adding code at that spot.
AnalogyIt is like assembling flat-pack furniture by the instructions and cutting a board yourself only for the shelf that is missing.
How to rememberLow means "little": the code is not zero, just a small amount.
No-code (ノーコード) is a development method that builds apps without writing any code, only by placing and configuring components on screen.
Even business staff with little programming knowledge can fairly easily build input forms or simple business apps themselves. What can be built stays within the components and settings the tool provides.
AnalogyIt is like picking finished furniture from a catalogue and deciding only its colour and where it goes.
How to rememberNo means zero: there is no point where you type code on the keyboard.
Exam points
Mix-upNo-code (ノーコード) builds within the provided features without writing code, while low-code (ローコード) can be extended by writing code for the missing parts.
Low-code vs. No-code
Aspect
Low-code
No-code
Key differenceAmount of code written
A little, only where needed
None
How features are extended
Code covers what components cannot
Limited to the tool's components and settings
Builders
Widely usable with some programming knowledge
Easy to use even with little programming knowledge
Key points
With a library, frequently used processing can be reused as components instead of being written yourself.
Making requests according to an API lets you use another program's functions without knowing its internal workings.
In a mashup, which builds a new service by combining existing published services and information, Web APIs and similar means are how those are pulled in.
Development methods centred on screen operations speed up development and make it easier for people other than professional developers to take part.