The indirect method used by almost every filer starts at net-income, adds non-cash-charges such as depreciation-accounting, amortisation and stock-based pay, then adds or subtracts change-in-working-capital. The result is the cash the operations actually threw off.
Comparing operating cash flow with net income over several years is the single fastest earnings-quality test. Cash that persistently lags profit means the profit is being booked before it is collected.
Example: Northwind Tools turns $78M of net income into $164M of operating cash flow: add $64M depreciation, $11M amortisation, $32M of stock-based pay, less $21M absorbed by working capital.
Related: free-cash-flow, change-in-working-capital, non-cash-charges, earnings-quality, cash-conversion