Apple stock jumped along with other tech shares Thursday, as markets cheered the Federal Reserve’s big interest-rate cut. Still, one strong day for the iPhone maker shouldn’t cloud the uncertainty ahead.

Apple ( AAPL 1.80%) has moved back into the top spot as the largest company in the world by market cap. It's gone through some stunning ups and downs, but if you'd bought shares at the initial public offering (IPO) back in 1980 and held on, you'd have a lot more shares, and a lot of money. Let's see just how much.

Shares of Apple Inc. advanced 1.80% to $220.69 Wednesday, on what proved to be an all-around dismal trading session for the stock market, with the NASDAQ Composite Index falling 0.31% to 17,573.30 and Dow Jones Industrial Average falling 0.