Who Reads Each Representation Before Behavior Happens?

Learning Question

Who reads each representation before behavior happens?

A stored file does not explain itself all the way down to behavior.

Take this command again:

python hello.py

There is not one reader. There is a chain of readers and owners of transitions.

The Command Has a Reader

The shell reads the command line.

It separates the command name from the argument:

command: python
argument: hello.py

The shell and operating system cooperate to locate the program to start. The details vary by platform and shell, but the important point is stable: the command text must be interpreted before any Python source file can run.

If python cannot be found, hello.py has not failed as Python code. The command failed before the interpreter ran it.

The Operating System Starts a Process

The operating system does not execute hello.py directly as Python source.

It starts a process for the Python interpreter executable. That process has an address space, environment variables, command-line arguments, standard streams, and other process-level state.

At this layer, the operating system is not deciding what print("hello") means. It is creating and managing the process that will run the interpreter.

That distinction matters:

OS starts python
Python reads hello.py

The file being passed as an argument is not the same thing as the process being started.

The Interpreter Reads the Source File

Inside the Python process, the interpreter reads hello.py.

Now the same bytes are interpreted as Python source code. The interpreter applies Python language rules: parse the text, prepare executable runtime material, execute top-level statements, resolve names such as print, and manage runtime behavior.

If the file contains:

print("hello")

Python treats that as a function call expression statement.

If the file contains broken syntax, the shell and operating system may have done their jobs correctly, but the interpreter rejects the source.

The Runtime Owns the Behavior

When the interpreter executes the code, it creates runtime state.

For this small script, the state is brief. For larger Python programs, the runtime may create modules, objects, function frames, imports, exceptions, open files, threads, or network connections.

The terminal output is also part of a chain. print writes to standard output. Standard output is connected to something: a terminal, a file, a pipe, or another process. The behavior you observe depends on that connection.

So the chain for hello.py is closer to:

command text
-> shell parses command
-> operating system starts Python process
-> Python interpreter reads hello.py
-> Python runtime executes code
-> standard output receives bytes
-> terminal displays text

Why Naming the Reader Matters

Each reader applies different rules.

An editor reads hello.py as text.

Python reads it as Python source.

The shell reads python hello.py as a command.

The operating system reads the Python executable as something it can start as a process.

The terminal reads output bytes and displays characters.

The same stored bytes become meaningful only through the reader that is using them at that moment.

The Durable Question

When an artifact appears in an execution path, ask:

Who reads this?
What rules does that reader apply?
What does that reader create or trigger next?
What evidence would show that this step succeeded?

This question works for Python source files, C executables, Java class files, shell scripts, configuration files, HTTP requests, logs, and stack traces.

Running is not magic added to a file. It is a chain of readers creating the next condition needed for behavior.