Examples

An investor has 500 shares of XYZ stock, valued at $10,000. He sells 5 call contracts for $1500, thus covering a certain amount of decrease in the XYZ stock (i.e. only after the stock value has declined by more than $1500 would the investor lose money overall). Losses can not be prevented, but merely reduced in a covered call position. If the stock price drops, the buyer of the call can not exercise the option because contractually the stock price must be above the strike price, and the seller (writer) keeps the money paid on the premium of the option, thus reducing his loss from a maximum $10000 to $10000-(premium).

This "protection" has its own disadvantage in which the investor is forced to sell his stock if the option is "called out" in which the writer is forced to sell his stock below market price or he must buy the calls back at a higher price than he sold them for.

The investor might repeat the same process again next month if he/she believes that stock will either fall or be neutral, if before expiration stock price does not reach strike price.

A call can be initiated sometimes even without ownership of underlying stock. If XYZ trades at $33 and $35 call trades at $1, than either can purchase 100 shares of XYZ and only sell one call. For this only $3200 is required to purchase the stock rather than $3300. The premium received for the call covers the decline made by the first $100 ($1 per share) in stock price. Thus $32 stock price is break-even point of the transaction. If the results are high, then profit and lower result means loss. In the above case, the upside potential limits more than $300 ($100 for selling call and $200 for increase in share price) to 35, which amounts to almost 10% return. The investor might repurchase the stock because he cannot participate, as he is required to sell call to 35. So he sell calls at higher strike price.