“If you were in the room with him and walked out, then came back in one minute later, he wouldn’t remember who you are,” the Herald’s source said. “He has a complete loss of short-term memory. His wife, Linda, has put him in full-time care.”

Young, a native of Scotland, founded AC/DC with his brother Angus in Australia in 1973. The band survived the death of Bon Scott, its hard-living frontman who sang classics such as “ T.N.T. ” and “ Rocker ,” in 1980. With replacement Brian Johnson out front, the band found success with the LP “Back in Black” — the second-best selling album of all time, according to the Richest . According to the band’s Web site , it has sold more than 200 million records.

“Malcolm is a big inspiration to me; he keeps me on my feet,” Angus — the band’s flashy guitarist known for playing in a schoolboy uniform — told Guitar World earlier this year. “Even when I’m tired from running around the stage for two hours, I’ll look back at what he’s doing and it gives me that boot up the backside I sometimes need. … Mal’s a very tough critic, and I know that if I can please him, I can please the world. A lot of people say, ‘AC/DC — that’s the band with the little guy who runs around in school shorts!’ But I wouldn’t be able to do what I do without Malcolm and the other guys pumping out the rhythm. They make me look good.”