Passive sentences ??

"A sentence is active when the subject is the doer (or the agent) of the action. A sentence
is passive when the subject is the receiver of the action." Have a look here: http://writingcenter.gmu.edu/resources/handouts/act_pass_sent.pdf

John threw the ball. Active

The ball was thrown to John. Passive

Mary created a sofware program. Active

A software program was created for Mary. Passive

In most cases, active voice is preferable. It is more dynamic and powerful. That said, you should use passive occasionally. Some academic stuff is mostly written in passive voice. I dislike it, but some people believe it more "scholarly."

"It is understood that A=B because blah blah blah."

Who understands? Why do they understand? Passive voice removes the "doer" agent.

Hope that helps.

Thanks a lot..... That answers my question. I was peeved at MS-Word underlining a lot of my sentences. I can see the error of my ways.
Thanks again

You are correct, kynguyen. "A software program was created for Mary" means that it was created for the benefit of Mary, or designed to her own personal specifications. It is unknown who created it. To indicate that, you must use the preposition "by": "A software program was created by Vivian for Mary."

There was a mistake in Mountain Hiker's example.

Where?

In a sentence in the passive voice, the construction that acted as subject in the active sentence becomes what is called "agent", and it is introduced by the preposition "by". That is, *if* it is needed at all. One of the most common reasons for using the passive voice is precisely the fact that the "doer" of the action is unimportant, unknown, or understood without the need of stating it in the sentence.

We both agree that the following sentence is active?

A) Mary created a sofware program. Active

Then, I wrote,

B) A software program was created for Mary. Passive

As you yourself mention that the doer of the action is unimportant, unknown, or understood without the need of stating it in the sentence. In the second example, I don't know who created the software program for Mary, nor do I care.

Sentences such as exemplified in the second example are common in everyday spoken and written English. As far as I know, sentence B is not active. If I throw that sentence into MS Word, it comes back as passive.

Imagine the following situation:

Juan: Did Mary get that custom software she needed?

Julie: Yes, a software program was created for Mary.

In this case, nobody knows or cares about who created the software.

I look forward to your reply.