Disgraced actor Bill Cosby, 81, has been moved to a general population unit four months after his prison sentence for sexual assault in Pennsylvania.

Cosby was moved after spending 16 weeks in special housing as he acclimatised to the SCI-Phoenix facility in Philadelphia.

He can now enjoy time roaming around the exercise yard, and even though he is designated legally blind, he can spend time in the prison library with assistance from other inmates.

The state prison spokeswoman Amy Worden said Cosby had a single cell and is not on a ward for older inmates.

Ms Worden said inmates there can spend several hours a day in the gym or exercise yard, and other time in the library, class or day room.

She said Cosby has inmates assigned to help him at times, given his age and disability but denied he had a “trustee” guiding him around.

“’Trustee’ is not even a word we use. We don’t have trustees, they’re inmate assistants who help the disabled. In his case, it’s public knowledge he’s visually impaired, so they would help guide him around,” she told the New York Daily Times.

“From what I understand from prison staff, he is going to the dining room,” she said of Cosby.

She told the the Times that Cosby is looking forward to socialising with other inmates in the general prison population.

“From what I understand from prison officials, the transition has been smooth and he’s happy to be out socialising with folks,” Ms Worden said.

She would not be drawn on whether Cosby is in a veteran’s unit: “He’s in a specialised unit, but I’m not going to say which one,” she told the Times.

Cosby is serving time for drugging and sexually assaulting a woman at his home in 2004.

-with AAP