SAN FRANCISCO: This much is known: Twitter grew out of Jack Dorsey's fascination with dispatch systems for cabs, emergency services and bike messengers. That fascination inspired the idea for a real-time communications system. In turn, that morphed into the short-form communications tool used by millions of people worldwide.

But precisely how Dorsey's idea turned into Twitter is a matter of dispute.

In Dorsey's version, he conceived Twitter on a San Francisco playground on his own.

But his one-time friend and co-worker, Noah Glass, maintains the seeds for Twitter were planted on the rain-slickened streets of San Francisco after a night of drinking vodka. In Glass's version, Glass and Dorsey sat for several hours in a car and discussed their lives and interests before the discussion touched upon Dorsey's fascination with schedules and people's status. Before they drove home that night, Glass wrote, "we created a story for status - a way to make it real and exciting for people. It was at that time that I decided that I was going to do everything I could to make sure that the ideas we were talking about would become something."

Blog entries and tweets from Twitter's early days leave little doubt that Glass was a key figure in the company's inception. He even came up with the name, according to "Hatching Twitter: A True Story of Money, Power, Friendship, and Betrayal," a new book that rehashes the company's origins.

Yet Dorsey's account makes no mention of him. By the time that Twitter started to gain critical mass in 2008, Glass had been exiled from the company. His name isn't mentioned in the regulatory filings for Twitter's IPO.

Glass' integral role in Twitter's creation is evident in past blog postings by fellow co-founders Evan Williams and Biz Stone, as well as early entries in his own Twitter account. Although Glass rarely posts there now, his Twitter account stands as a monument to his contributions. His profile description declares, "i started this," and his first tweet at the bottom of the feed says, "just setting up my twittr." That statement was posted at 1 pm PT on March 21, 2006, just 10 minutes after Dorsey had tweeted the identical words.

Twitter didn't open itself to all comers until July 2006. That was when Glass ruminated on the service's origins in a blog entry that's still online.

"I am committed to it's (sic) existence," Glass wrote at the time.

But Glass didn't get to stick around. He was pushed out of the company as part of a campaign orchestrated by Dorsey, according to the book.

Dorsey got booted as CEO in 2008 and shifted over to chairman, a role he still holds. Williams, Twitter's largest shareholder, served as CEO for two years before he was replaced by Dick Costolo, who had been brought as chief operating officer. Costolo, a former stand-up comic, heralded his arrival at Twitter by tweeting: "Task (hash)1: undermine CEO, consolidate power."

Since taking over as CEO, Costolo has poured more money into data centers to prevent Twitter from breaking down as frequently as it had in its early days. He also groomed the San Francisco company for an initial public offering that was priced Wednesday evening at $26 a share, valuing the company at more than $18 billion.