Mr. Hallac, known to all as Charlie, was the first official employee to be hired at BlackRock when the firm opened its doors in 1988. Under its chief executive, Laurence D. Fink, who founded the firm along with seven others, BlackRock is now the largest publicly traded fund management company in the world, overseeing $4.7 trillion. Mr. Hallac’s specialty was in operations and technology, and he bought the firm’s first computer server in 1988. He is credited with conceiving of and putting in place BlackRock’s industry-leading investment platform, Aladdin. Aladdin is, in effect, a nervous system that unites and connects BlackRock’s main trading, risk management and communication functions. It was an innovative step at the time, because most investment management firms, unlike their investment banking counterparts, did not have sophisticated technology operations. But Mr. Hallac and Mr. Fink, who had worked together at First Boston as mortgage professionals, had a vision of an entrenched risk management system that would be unique to BlackRock and ensure that the firm’s traders and investors were all on the same page when it came to making investment decisions. The Aladdin operating system is now used by 70 financial firms worldwide. Mr. Hallac became the firm’s chief operating officer in 2009 and played a central role in the integration of Barclays Global Investors, the index giant that BlackRock purchased in 2009. He is survived by his parents, David and Linda; his wife, Sarah; and three children, David, Rebecca and A.J.