Learn Hardcore Turkish: Yönerge net olsun diye adımları tek tek yazdım. - I wrote the steps one by one so the instructions would be clear.

It introduces a purpose clause: ... olsun diye means “so that ... (will) be.” Here, Yönerge net olsun diye = “so that the instruction is clear.” The verb is in the optative mood (a “let it be”/desired outcome), which is standard for purpose clauses with diye.

Why is it olsun and not olmak or something else?

Olsun is the 3rd person singular optative of ol- “to be,” used to express a wished-for result. With diye, Turkish prefers a finite verb in the optative: “(so that it) be (clear).” Using the bare infinitive olmak here would be ungrammatical with diye.

Can I say Yönergenin net olması için adımları tek tek yazdım instead?

Yes. That’s also natural and a bit more formal/neutral. Differences:

... olsun diye: slightly more colloquial and direct, feels like “so that it will be (clear).”
... olması için: uses a nominalized clause with için “for/in order to,” stylistically a touch more formal. Meaning is the same.

What is the subject of olsun?

Yönerge is the subject of the subordinate clause: “[The instruction] be clear.” The main clause’s subject is “I,” expressed by the verb ending -dım in yazdım.

Why is it adımları with the accusative -ı?

Because it’s a definite direct object: “the steps.” In Turkish, definite objects take the accusative. Without the accusative, it would sound indefinite/generic (“(some) steps”), and even then Turkish often prefers either the bare singular for an indefinite plural (e.g., “birkaç adım yazdım”) or a quantifier. Here we want the specific set of steps, hence adım-lar-ı.

Could adımları also mean “his/her steps”?

Yes, morphologically it can be ambiguous:

adımlar-ı = “the steps” (plural + accusative)
adım-lar-ı = “his/her steps” (plural + 3rd person possessive) Context disambiguates. If you meant “his/her steps” explicitly, you’d normally say onun adımlarını.

Is the word order fixed? Can I move the purpose clause?

You can move it:

Yönerge net olsun diye adımları tek tek yazdım. (neutral)
Adımları tek tek yazdım, yönerge net olsun diye. (colloquial, afterthought) Both are fine. Placing the purpose clause first is very common.

Do I need a comma after ... diye?

Not required. You’ll see both with and without a comma. With a long fronted clause, some writers add a comma for readability, but it’s optional: Yönerge net olsun diye(,) adımları tek tek yazdım.

What exactly does tek tek mean? How is it different from similar expressions?

Tek tek = “one by one, individually,” emphasizing enumeration of each item.

Teker teker: near-synonym, a bit more colloquial.
Birer birer: “one by one,” slightly more literary.
Adım adım: “step by step” in the sense of gradually/progressively; it doesn’t necessarily mean you listed each step as separate items. So here tek tek fits better than adım adım.

Why singular yönerge and not plural yönergeler?

Yönerge often refers to the whole instruction set as one unit. Use plural only if you mean multiple separate directives: Yönergeler net olsun diye... = “so that the instructions (plural) are clear.”

Are there natural synonyms for yönerge here?

Yes, depending on nuance:

talimat(lar): “instruction(s),” more command-like.
kılavuz: “guide/manual.”
rehber: “guide,” often person or document. Your sentence could also be phrased as: Talimat(lar) net olsun diye... if you mean procedural instructions.

Could I say daha net to express “clearer”?

Yes: Yönerge daha net olsun diye adımları tek tek yazdım. That slightly changes the meaning from “be clear” to “be clearer,” implying an improvement.

Does diye have other uses I should know?

Yes. Besides purpose, diye also marks reported speech/thought or reason/motive:

‘Hadi’ diye bağırdı = “He shouted ‘Come on.’”
Yanlış anlaşılmasın diye = “So that it won’t be misunderstood.” In your sentence, it’s the purpose use.

Is there a way to say this with ki?

Possible but less common: Adımları tek tek yazdım ki yönerge net olsun. It’s more speech-like and adds a slight explanatory tone (“...so that...”). ... olsun diye is the go-to pattern.

Can you break down the morphology of the sentence?

Yönerge = instruction/guideline (subject of the subordinate clause)
net = clear
ol-sun = be-OPT.3SG (“let it be”/“so that it be”)
diye = so that (purpose marker)
adım-lar-ı = step-PL-ACC (“the steps”)
tek tek = one by one
yaz-dı-m = write-PAST-1SG (“I wrote”)