Parşömende sayı kilidinin kodu yazıyordu.

It is parşömen + -de.

• parşömen = parchment
• -de = the locative case, meaning in / on / at

So parşömende means on the parchment in this sentence.

This suffix changes form because of vowel harmony and consonant voicing.

The locative has four common forms:

• -de
• -da
• -te
• -ta

Why -de?

• The last vowel in parşömen is e, so it needs the front-vowel version: -de / -te
• The word ends in n, which is voiced, so Turkish uses d, not t

That gives parşömende.

It is a very common Turkish noun compound.

• sayı = number
• kilit = lock

In English, you can often put two nouns together directly, like number lock. In Turkish, the second noun usually takes a compound ending, typically -(s)ı / -(s)i / -(s)u / -(s)ü.

So:

• sayı kilidi = number lock or combination lock

Because when kilit takes a vowel-initial ending, the final t often softens to d.

So:

• kilit
  • -i → kilidi

This is a normal sound change in Turkish. You will see the same kind of thing in many words.

Because sayı kilidi becomes the possessor of the next noun, kodu.

In Turkish, when one noun possesses another, the possessor takes the genitive ending.

So:

• sayı kilidi
  • -nin → sayı kilidinin

The full idea is:

• sayı kilidinin kodu = the code of the number lock

Because in a possession structure, the possessed noun also gets an ending.

So in:

• sayı kilidinin kodu

the first part is the possessor, and the second part is the possessed item.

That means:

• kod
  • -u → kodu

This ending does not mean his/her code here. It is the normal marker showing that code belongs to the number lock.

It breaks down like this:

• yaz- = write
• -ıyor = progressive
• -du = past

So form-wise, it is was writing.

But in Turkish, when the subject is text, words, or something written, yazıyor / yazıyordu often means:

• was written
• it said
• you could read

So here, yazıyordu is best understood as something like was written there or it said there.

They are similar, but not identical.

• yazıyordu: narrative/descriptive, often like it was written there or it said
• yazılıydı: more stative, simply it was written
• yazdı: usually means wrote, which sounds more like an action performed by a writer

So yazıyordu works well in a story-like context where the speaker is describing what appeared on the parchment at that moment.

Not completely. Turkish word order is flexible, although the verb usually stays at the end.

In this sentence:

• Parşömende = location
• sayı kilidinin kodu = subject
• yazıyordu = verb

Starting with Parşömende puts the location first and sets the scene. It is a natural way to emphasize where the writing was.

Because Turkish does not have an article that works like English the.

Definiteness is usually understood from:

• context
• possession structures
• case marking
• word order

Here, sayı kilidinin kodu already sounds definite because it means a specific code belonging to a specific lock.

Turkish can use bir for a / an / one, but there is no obligatory word corresponding to English the.