The updates come in pairs that are each for the MacBook, MacBook Pro, and MacBook Air introduced in October.
One update in the pair fixes "several issues to improve the stability" of the computers, Apple said. The other "improves the sensing and accuracy" of the power adapter and battery charge indicator lights.
The fixes can be installed automatically through Apple's Software Update service, which downloads and installs updates from the Web. However, for cases where the updates have to be installed manually, Apple has posted instructions on its support site. Apple also has a download page for all six updates, as well as a page for general information.
Apple chief executive Steve Jobs unveiled the lighter aluminum MacBooks in time for the holiday shopping season. The aluminum casing, common with the MacBook Pro, was introduced for the first time in the less-expensive MacBook line.
At the same time, Apple lowered the price of the entry-level, 13-inch white plastic MacBook by $100 to $999. By taking the system below $1,000, Apple broke a psychological barrier that could sway some consumers looking at Windows notebooks in the same price range, analysts said.
In marketing the latest machines, Jobs made a big deal over the new unibody design. Rather than stitch together several pieces of aluminum, Apple uses a manufacturing process that starts with one piece of metal and carves out the product. As a result, the notebooks are slightly thinner and lighter than the previous generation.