He attended a graduation ceremony in the capital, Harare.
Mr Mugabe had been under house arrest for days. The army made its move after a power struggle over his successor.
The military said on Friday it was “engaging” with Mr Mugabe and would advise the public on the outcome of talks “as soon as possible”.
Meanwhile Christopher Mutsvangwa, the leader of the influential war veterans’ association, said Mr Mugabe should step down at once.
He called for a huge turnout in street protests on Saturday.
“We want to restore our pride and tomorrow is the day… we can finish the job which the army started, Mr Mutsvangwa said.
“There’s no going back about Mugabe. He must leave.”
Mr Mugabe’s attendance at the graduation is an annual tradition but few expected to see him there, the BBC‘s Andrew Harding reports from Zimbabwe.
Mr Mugabe walked slowly up a red carpet and joined the crowd in singing the national anthem, then opened the graduation ceremony at Zimbabwe’s Open University, where he is chancellor.
One of the people he conferred a degree upon was Marry Chiwenga, the wife of the general who detained him on Wednesday, the state broadcaster reports.
Neither the 93-year-old president’s wife, Grace Mugabe, nor Education Minister Jonathan Moyo – an ally of hers whose house was reportedly raided by the military – were present.
The army acted after Mr Mugabe sacked Vice-President Emmerson Mnangagwa last week.
Mr Mnangagwa was seen as a potential successor and his sacking was supposed to pave the way for Grace Mugabe – who is four decades younger than him – to take over the presidency instead.
It was thought she had left the country but it emerged on Thursday that she was at home with Mr Mugabe.