Given the astronomical growth of the Android operating system, the latest numbers from comScore on the U.S. smartphone market don’t come as much of a surprise.

Android’s market share leaped more than 7 percentage points to 31.2 percent between October and January, putting the operating system in first place ahead of Research In Motion’s (RIM) BlackBerry platform and Apple’s iPhone.

ComScore reports indicate the operating system’s market share has more than quadrupled over the past year as carriers have released a bevy of popular Android-based smartphones, including Motorola’s Droid franchise with Verizon Wireless and Samsung’s Galaxy S lineup.

Android’s growth has eroded the portion of the market held by RIM’s BlackBerry devices and the iPhone. RIM’s market share slipped more than 5 percentage points over the last three months of 2010 to 30.4 percent, putting it in second place. The iPhone’s market share was nearly flat during the same period, gaining one-tenth of a percentage point to bring its share of the U.S. smartphone market to 24.7 percent.

Microsoft and Palm rounded out the top five U.S. operating systems, with 8 percent and 3.2 percent, respectively.

ComScore also reported market share numbers for U.S. device manufacturers. Nokia got knocked out of the top five spot as Apple’s market share reached 7 percent. Other than Apple’s ascension, the positions of the remaining top four OEMs in the United States remained steady. Samsung held its top spot with 24.9 percent, LG ranked second with 20.8 percent, followed by Motorola with 16.5 percent and RIM with 8.6 percent.

The numbers on smartphone and manufacturer market share came from comScore’s MobiLens service, which surveyed more than 30,000 wireless subscribers in the United States to track trends in the U.S. mobile phone industry during the last three months of 2010.

Google tweeted from its @AndroidDev Twitter account that the company’s Android Market has surpassed 100,000 downloadable apps.

As more developers hop on the Android train, the number of apps in the Android Market has grown almost exponentially. It was just seven months ago that the Android Market reported 30,000 downloadable apps.

By comparison, Apple’s App Store currently offers just under 300,000 downloadable apps. It took the App Store just under 500 days to reach the 100,000 mark, while it took the Android Market just under 800 days to reach that same milestone.

Google’s open-source Android operating system has seen tremendous growth over the past year, supplanting even Apple’s iOS in U.S. mobile operating system market share. Android has been helped along by OEMs like Motorola and HTC, both of which have built popular smartphones around Google’s OS.

Google has released a new piece of software called App Inventor that allows lay users to create relatively complex mobile applications for the Android platform. According to a blog posted on Google’s website, the new system will allow users who don’t know a shred of programming to create apps by dragging and dropping commonly used “blocks” of Java code into a template.

App Inventor allows users to create apps that are sophisticated enough that they can store data created by users in a database. Users also can create apps that use GPS location information and automatically send text messages.

The blocks editor uses the Open Blocks Java library for creating visual blocks programming languages. Open Blocks is distributed by the Massachusetts Institute of Technology’s Scheller Teacher Education Program and derives from thesis research by Ricarose Roque. Open Blocks visual programming is closely related to the Scratch programming language, a project of the MIT Media Laboratory’s Lifelong Kindergarten Group.

The compiler that translates the visual blocks language for implementation on Android uses the Kawa Language Framework and Kawa’s dialect of the Scheme programming language, developed by Per Bothner and distributed as part of the Gnu Operating System by the Free Software Foundation.