SAN FRANCISCO >> Apple is expected to step up its efforts to boost recently slumping iPad sales with the unveiling of its latest tablet computer at an Oct. 16 event.

The showcase also is expected to feature an update to the operating system for its Mac computers and the possible release of a new digital payment service called Apple Pay. The company’s new iPhones released last month include a wireless chip equipped to make the payments, but the service isn’t available yet.

In keeping with its usual practice, Apple Inc. isn’t saying what’s on the agenda. Instead, a cryptic invitation sent Wednesday to reporters and analysts simply said: “It’s been way too long.”

This is the time of the year that Apple typically releases its latest products to cash in on the holiday shopping season. The company’s last tablet, the iPad Air, came out nearly a year ago.

Although it’s Apple’s sleekest tablet yet, the iPad Air hasn’t proven compelling enough to accelerate the company’s tablet sales. After a solid performance in last year’s holiday shopping season, Apple’s iPads have faltered. Through the first half of this year, Apple had shipped 29.6 million iPads, a 13 percent drop from the same time last year.

Since the first model was released in April 2010, Apple has sold more than 225 million iPads. Many people are still using iPads that they bought several years ago because the recent generations haven’t prompted them to spend another $500 to $700 for a new tablet. Apple also has been facing tougher competition from a variety of tablet makers using Google’s free Android software, as well as from Microsoft Corp.’s rival device, the Surface.

Speculation about the next iPad has centered on the possible inclusion of a sensor that enables a device to be unlocked with a user’s fingerprint instead of a password. The feature, called Touch ID, has been available on Apple’s last two iPhone models. Apple also might offer an iPad with a gold-colored casing, another option already available on iPhones.

Apple’s most recent iPhone includes a hot-selling model with a 5.5-inch display screen. Some analysts believe the bigger iPhone might siphon sales from Apple’s iPad Mini, which has a 7.9-inch screen. The standard iPad boast a nearly 10-inch screen.

An operating system update called “Yosemite” is also due out for Apple’s line of Mac computers, making it likely that the software will also be a part of the Oct. 16 event to be held at the company’s headquarters in Cupertino, California.