Three words get used as though they were one thing — software. They do different jobs, and the difference explains who is responsible when something breaks.
An operating system manages the machine: it decides which program gets the processor next, hands out memory, owns the files, and speaks to the hardware so that no one else has to. macOS, Windows, Linux, Android, iOS.
A programming language is a notation for writing instructions, plus the tools that carry them out. Python, C, Java, JavaScript. A language is not a program you run; it is the means by which programs get written.
An application is a program written for a person to use to do something: a browser, a photo editor, the game you played at lunch, the script you wrote last week.
graph TD A["Applications<br/>browser, editor, your program"] --> O["Operating system<br/>files, memory, scheduling, devices"] O --> H["Hardware<br/>CPU, RAM, storage, screen"] L["Programming language<br/>and its tools"] -.->|used to write| A
Your open("data.txt") is a good example of the stack doing its job.
Python does not know how your drive stores anything. It asks the
operating system, which knows the file system, which asks the storage
device. Three layers, one line of yours — and the same line works on a
different machine because the layer underneath changed instead of you.
That is also how blame gets assigned. A program that cannot find a file it was given is your bug. A program that cannot save because the disk is full is the operating system telling you the truth. A program that runs on your laptop but not a classmate’s is usually neither: it is a missing part of the language’s tooling, which is what Setting Up Python exists to prevent.
Curriculum connection
C3.5
explain the difference between the functions of applications, programming languages, and operating systems.
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