As of Feb. 29, 2016, information technology accounts for the largest sector allocation in the Standard & Poor's (S&P) 500. Of the index's 500 components, 68 are categorized as information technology companies, accounting for a 20% total weighting in the index. Due to the index's reputation as the most popular benchmark for the broad stock market, many exchange-traded funds (ETFs) try to replicate the overall performance of the S&P 500 after expenses.

The SPDR S&P 500 ETF (NYSEARCA: SPY) is the largest such ETF with assets of over $171 billion, as of Feb. 29, 2016. Its goal of providing exposure to many of the largest and most well-established companies in the United States makes it an ideal core holding for many portfolios. As such, many of the biggest technology names in the index come from the sector's most recognizable brands.

Apple

Apple, Inc. (NASDAQ: AAPL) carries the largest weighting in the entire S&P 500 Index. What began as purely a computer company when the business was launched in 1976 has since grown into a global technology giant. Apple had a market cap of approximately $7 billion when the iPod debuted in late 2001. Since then, Apple has developed the iPhone, iPad, Apple Watch, Apple TV and the Mac lineup of personal computers (PCs).

Apple's total market cap peaked at over $750 billion in the first half of 2015. As of March 1, 2016, it now sits at roughly $555 billion.

Apple represents approximately 3.2% of the SPDR S&P 500 ETF's total assets as of Feb. 29, 2016.

Microsoft

Microsoft Corporation (NASDAQ: MSFT) is the developer and manufacturer of Microsoft Office and the Windows operating system. As the consumer personal computing marketplace has moved away from desktop and laptop computers and toward tablets and smartphones, Microsoft has diversified its product line to include the Xbox gaming system, the Surface tablet and its developing cloud services segment.

Microsoft captured the title of largest company in the world by market share in 1998 and held it until 2000. It held the title on and off from 2002 to 2003. As of Feb. 29, 2016, Microsoft is the second-largest company overall in the S&P 500.

Microsoft represents approximately 2.4% of the SPDR S&P 500 ETF's total assets as of Feb. 29, 2016.

Facebook

Founded in 2004, Facebook, Inc. (NASDAQ: FB) is the administrator of the popular social networking site that boasts nearly 1.6 billion monthly active users as of Dec. 31, 2015. Generating most of its revenue through various forms of advertising on the site, Facebook made a total of nearly $18 billion in revenue in 2015.

In one of the most anticipated initial public offerings (IPOs) in Wall Street history, Facebook went public on May 18, 2012. Based on its IPO share price of $38, the company was then valued at over $100 billion. As of Feb. 29, 2016, Facebook is the third-largest technology component of the S&P 500 and the seventh-largest component overall, with a market cap of $310 billion.

Facebook represents approximately 1.4% of the SPDR S&P 500 ETF's total assets as of Feb. 29, 2016.

Alphabet Class A

Formerly known as Google, Alphabet, Inc. (NASDAQ: GOOGL) is the global conglomerate created in 2015 to serve as the parent company of Google and several other companies owned by Google.

Prior to the creation of Alphabet, Google executed a two-for-one stock split on April 3, 2014. The split resulted in two share classes of Google stock: the Class A shares and the Class C shares. The two share classes are differentiated primarily by the voting rights that come with each. Each Class A share comes with a single vote.

Alphabet Class A represents approximately 1.2% of the SPDR S&P 500 ETF's total assets as of Feb. 29, 2016.

Alphabet Class C

Unlike the Class A shares, the Class C shares of Alphabet, Inc. (NASDAQ: GOOG) come with no voting rights. Combined, the two share classes would represent nearly 2.5% of the S&P 500 and would be the second-largest overall component of the index. The mechanics of the stock split, however, treats them as two individual stocks with separate ticker symbols, and each share class gets half the weighting of the whole.

Alphabet Class C represents approximately 1.2% of the SPDR S&P 500 ETF's total assets as of Feb. 29, 2016.