يشفر صديقي النسخة الاحتياطية في الحاسوب.

It is a verbal sentence with this order:

يشفر = verb
صديقي = subject
النسخة الاحتياطية = direct object
في الحاسوب = prepositional phrase

So the pattern is:

Verb + Subject + Object + Prepositional phrase

That is very common in Modern Standard Arabic. In English, we usually start with the subject instead, so the word order feels different.

يشفر means he encrypts or he encodes.

In careful vocalization, it would be يُشَفِّرُ. The verb is from شفّر, a Form II verb often used for to encrypt / encode.

In normal Arabic writing, short vowels and the shadda are usually omitted, so يشفر is just the unvocalized spelling of يُشَفِّرُ.

It can mean either, depending on context.

The Arabic imperfect verb often covers:

• simple present: encrypts
• present progressive: is encrypting
• habitual action: regularly encrypts

So without more context, يشفر is flexible. If the sentence is just presented as a plain fact, encrypts is a natural translation.

Because صديق means friend, and the suffix -ي means my.

So:

• صديق = friend
• صديقي = my friend

This is a very common Arabic pattern. Instead of using a separate word for my, Arabic usually adds a suffix to the noun.

Because صديقي is already definite by possession.

In Arabic, a noun with a possessive suffix like -ي is automatically definite:

• صديق = a friend / friend
• صديقي = my friend

So الصديقي would not be correct here.

A few things help:

1. After a verb, Arabic often places the subject right after it.
2. Semantically, my friend is clearly the one doing the action.
3. The noun phrase النسخة الاحتياطية fits naturally as the thing being encrypted, so it is the direct object.

If full case endings were written, the subject would be nominative and the object accusative. In normal unvocalized writing, those endings are usually not shown.

Because الاحتياطية is an adjective describing النسخة.

In Arabic, adjectives must agree with the noun they describe in:

• definiteness
• gender
• number
• case

So if the noun is definite:

• النسخة = the copy

then the adjective must also be definite:

• الاحتياطية = the backup

Together:

• النسخة الاحتياطية = the backup copy / the backup

Because it describes نسخة, and نسخة is a feminine noun.

Arabic adjectives agree with the nouns they modify, so:

• نسخة احتياطية = a backup copy
• النسخة الاحتياطية = the backup copy

The feminine ending here is part of that agreement.

Literally, في الحاسوب means in the computer.

But in natural English, depending on the situation, you might translate it as:

• in the computer
• on the computer

Arabic في often covers location more broadly than English in does. So the exact English wording may change with context, even though the Arabic is the same.

Yes, that is also correct.

Compare:

• يشفر صديقي النسخة الاحتياطية في الحاسوب
• صديقي يشفر النسخة الاحتياطية في الحاسوب

The first begins with the verb, which is very common in MSA.
The second begins with the subject, which can sound slightly more direct or slightly more emphatic on my friend.

Both are grammatical.

A fully vocalized version would be:

يُشَفِّرُ صديقي النُّسْخَةَ الاحتياطيةَ في الحاسوبِ

A few useful things to notice:

• يُشَفِّرُ: the verb ends in -u
• النُّسْخَةَ: the direct object has -a
• الاحتياطيةَ: the adjective matches the object in case
• الحاسوبِ: after في, it is in the genitive, so it ends in -i

In everyday Arabic writing, these short vowels are normally omitted.