## Program and Process

We will talk a lot about the running "**process**", so it's useful to have clarity about what it means, and what's the difference with the word "**program**".

### What is a Program

The word **program** is commonly used to describe many things:

* The **code** that you write, the **Python files**.

  // `lastTransitionTime` is the last time the condition transitioned from one status to another.
  optional k8s.io.apimachinery.pkg.apis.meta.v1.Time lastTransitionTime = 3;

  // `reason` is a unique, one-word, CamelCase reason for the condition's last transition.
  optional string reason = 4;

  // `message` is a human-readable message indicating details about last transition.
  optional string message = 5;
}

  // `lastTransitionTime` is the last time the condition transitioned from one status to another.
  optional k8s.io.apimachinery.pkg.apis.meta.v1.Time lastTransitionTime = 3;

  // `reason` is a unique, one-word, CamelCase reason for the condition's last transition.
  optional string reason = 4;

  // `message` is a human-readable message indicating details about last transition.
  optional string message = 5;
}

```Python hl_lines="7"
{!../../../docs_src/path_params_numeric_validations/tutorial003.py!}
```

* 🚨 Avoid using `Optional[SomeType]`
* Instead ✨ **use `Union[SomeType, None]`** ✨.

Both are equivalent and underneath they are the same, but I would recommend `Union` instead of `Optional` because the word "**optional**" would seem to imply that the value is optional, and it actually means "it can be `None`", even if it's not optional and is still required.

I think `Union[SomeType, None]` is more explicit about what it means.

* ✏ Fix typo about file path in `docs/en/docs/tutorial/bigger-applications.md`. PR [#3285](https://github.com/tiangolo/fastapi/pull/3285) by [@HolyDorus](https://github.com/HolyDorus).
* ✏ Re-word to clarify test client in `docs/en/docs/tutorial/testing.md`. PR [#3382](https://github.com/tiangolo/fastapi/pull/3382) by [@Bharat123rox](https://github.com/Bharat123rox).

            ; esclientDiFile = esclient.xml
            ; esfluteDiFile = esflute_config.xml
        }
        ; fess_config.elevate_word = map:{
            ; package = config
            ; esclientDiFile = esclient.xml
            ; esfluteDiFile = esflute_config.xml
        }
        ; fess_config.elevate_word_to_label = map:{
            ; package = config
            ; esclientDiFile = esclient.xml

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* Frontend **Vue** :
    * Généré avec Vue CLI.
    * Gestion de l'**Authentification JWT**.
    * Page de connexion.
    * Après la connexion, page de tableau de bord principal.
    * Tableau de bord principal avec création et modification d'utilisateurs.
    * Modification de ses propres caractéristiques utilisateur.
    * **Vuex**.
    * **Vue-router**.

## Server Machine and Server Program

There's a small detail about names to keep in mind. 💡

The word "**server**" is commonly used to refer to both the remote/cloud computer (the physical or virtual machine) and also the program that is running on that machine (e.g. Uvicorn).