Learn Hardcore Japanese: sensei ha pasokon wo naosimasu.

は is the topic marker. It tells us the sentence is “about” 先生 (the teacher). Rather than emphasizing who performs the action (which が would do), は sets the scene: “As for the teacher, …”

What does を indicate here?

を marks the direct object of the verb. It shows that パソコン (the computer) is what is being fixed. In English, it’s like saying “fix the computer.”

What form and meaning does 直します have? Is it past, present, or future?

直します is the polite non-past (present/future) form of the transitive verb 直す.

Meaning: “to fix,” “to repair” (you actively repair something).
Non-past can mean either present (“fixes”) or future (“will fix”) depending on context.

Why is the verb 直します placed at the end of the sentence?

Japanese follows a Subject-Object-Verb (SOV) word order. That means the verb almost always comes last, after the topic/subject and any objects.

Why is パソコン written in katakana rather than kanji or hiragana?

パソコン is a loanword (from “personal computer”), and Japanese writes foreign-origin words in katakana.

Can I omit 先生は and just say パソコンを直します?

Yes. If the context already makes it clear who is doing the fixing, you can drop the topic. パソコンを直します then simply means “(I/they) fix the computer,” but you’d need context to know who “(I/they)” refers to.

What’s the difference between 直す and 直る?

直す is transitive: you fix something. (You do the repairing.)
直る is intransitive: something gets fixed. (It becomes repaired, without naming the agent.)

Could I use 修理します instead of 直します?

Yes. 修理する also means “to repair,” especially machinery or equipment.

直す can be a bit more general (like correcting errors or mending).
修理する feels more technical or formal.

What changes if I replace は with が, as in 先生がパソコンを直します?

Using が marks 先生 as the grammatical subject and often introduces new information or emphasizes who does the action: “It is the teacher who fixes the computer.” In contrast, は assumes 先生 is already known and comments on what they do.