A warrant differs from a standard call option in that when a warrant is exercised, the firm whose stock is being purchased will have an increase in cash; this is not the case when a standard call option is exercised. Both the warrant and the call option give the holder the right to purchase shares of a firm's stock, but the writer (seller) of a warrant is the firm itself whereas the writer of a standard call option is simply another investor. Upon exercising a warrant, the investor buys the stock from the firm itself, which increases the firm's cash account. When a call option is exercised, another investor's cash account is increased. For the same reason, when a call option is exercised, nothing happens to the outstanding shares of the firm; but when a warrant is exercised, the firm's outstanding shares will increase.