The non-GAAP financial measures included in the tables adjust for the following items: business combination accounting entries, stock-based compensation expense, restructuring and transition charges, charges related to the amortization of intangible assets, impairments of assets and certain other items. We believe the presentation of these non-GAAP financial measures, when taken together with the corresponding GAAP financial measures, provides meaningful supplemental information regarding the Company's operating performance for the reasons discussed below. Our management uses these non-GAAP financial measures in assessing the Company's operating results, as well as when planning, forecasting and analyzing future periods. We believe that these non-GAAP financial measures also facilitate comparisons of the Company's performance to prior periods and to our peers and that investors benefit from an understanding of these non-GAAP financial measures.
Stock-based compensation: Consists of expenses for employee stock options, restricted stock units, restricted stock awards, performance based awards and our employee stock purchase plan determined in accordance with the authoritative guidance on stock-based compensation. When evaluating the performance of our individual business units and developing short and long term plans, we do not consider stock-based compensation charges. Our management team is held accountable for cash-based compensation, but we believe that management is limited in its ability to project the impact of stock-based compensation and accordingly is not held accountable for its impact on our operating results. Although stock-based compensation is necessary to attract and retain quality employees, our consideration of stock-based compensation places its primary emphasis on overall shareholder dilution rather than the accounting charges associated with such grants. In addition, for comparability purposes, we believe it is useful to provide a non-GAAP financial measure that excludes stock-based compensation in order to better understand the long-term performance of our core business and to facilitate the comparison of our results to the results of our peer companies. Furthermore, unlike cash-based compensation, the value of stock-based compensation is determined using complex formulas that incorporate factors, such as market volatility, that are beyond our control.
Three months ended December 28, December 30, 2012 2011 ------------ ------------ Cost of revenue $ 4 $ 4 Sales and marketing 18 20 Research and development 13 13 General and administrative 7 9 ------------ ------------ Total stock-based compensation $ 42 $ 46 ============ ============
Amortization of intangible assets: When conducting internal development of intangible assets, accounting rules require that we expense the costs as incurred. In the case of acquired businesses, however, we are required to allocate a portion of the purchase price to the accounting value assigned to intangible assets acquired and amortize this amount over the estimated useful lives of the acquired intangible assets. The acquired company, in most cases, has itself previously expensed the costs incurred to develop the acquired intangible assets, and the purchase price allocated to these assets is not necessarily reflective of the cost we would incur in developing the intangible asset. We eliminate these amortization charges from our non-GAAP operating results to provide better comparability of pre- and post-acquisition operating results and comparability to results of businesses utilizing internally developed intangible assets.