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stock and warrants, based on the treasury stock method, convertible debentures and preferred stock, based on the if-converted method, and other commitments to be settled in common stock. The calculations of basic and diluted net income (loss) attributable to common shareholders per share and basic and diluted weighted average shares outstanding are as follows (in thousands, except per share data): 

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The following dilutive effect of potential common shares was excluded from the calculation of dilutive weighted average shares outstanding as their effect would be anti-dilutive (in thousands): 

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## (k) Concentration of Credit Risk 

Financial instruments that potentially subject the Company to concentrations of credit risk are principally cash and cash equivalents, short-term investments, accounts receivable and installments receivable. The Company places its cash and cash equivalents and investments in highly rated institutions. Concentration of credit risk with respect to receivables is limited to certain customers (end users and distributors) to which the Company makes substantial sales. To reduce risk, the Company routinely assesses the financial strength of its customers, hedges specific foreign installments receivable and routinely sells its installments receivable to financial institutions with limited recourse and without recourse. As a result, the Company believes that the accounts and installments receivable credit risk exposure is limited. As of June 30, 2002 and 2003, the Company had no customers that represented 10% of total accounts and installments receivable. 

## (l) Allowance for Doubtful Accounts 

The Company makes judgments as to its ability to collect outstanding receivables and provide allowances for the portion of receivables when it is probable that a loss has been incurred. Provisions are made based upon a specific review of all significant outstanding invoices. In determining these provisions, the Company analyzes its historical collection experience and current economic trends. 

## (m) Financial Instruments 

Financial instruments consist of cash and cash equivalents, short-term investments, accounts receivable, installments receivable, foreign exchange contracts and 5$^{1}$/ 4 % convertible subordinated debentures. The estimated fair value of these financial instruments approximates their carrying value and, except for accounts receivable and installments receivable, is based primarily on market quotes. 

