作文 and 写す: composing a text and copying existing wording
Compare a composition about summer vacation with blackboard text copied character by character. Writing in a notebook does not by itself establish original composition.
Composing and revising a text
作文 (さくぶん) means composing a text or the composition produced. 「夏休みの思い出を作文に書いた。」 says summer vacation memories were written in a composition.
「先生が私の作文を丁寧に直してくれた。」 says the teacher carefully corrected the speaker’s composition. Distinguish the speaker’s text from the teacher’s revision of it.
Copying existing text
写す (うつす) means copying in this comparison. 「黒板の文章を一字ずつノートに写した。」 says the text on the blackboard was copied into a notebook one character at a time.
「窓辺の花を写真に写す。」 describes photographing flowers by the window. This is another meaning of 写す, identified through the object and 写真に.
The relationship to existing wording
Writing in a notebook can be copying blackboard text rather than composing a piece about one’s memories. The act of writing alone does not establish 作文.
A composition can contain a quotation; it need not consist entirely of newly invented wording. Distinguish a copied passage from the work of organizing the text as a whole.
Is 「黒板の文章を一字ずつノートに写した。」 an original composition of the speaker’s memories?
Show the answer and why
No. It describes copying existing blackboard text into a notebook character by character. The notebook as the writing location does not make the task original composition.