一般兌換率是以預設的比率便可以了，例如： 美金兌港幣7.8
而兌換率是不需要日日改變的
每次出單的時候只需用預設的匯率便可以了
到結帳的時後才輸入 年結的兌換率， 然後產生匯率盈虧
例如：到年结時，2018年3月31日， 假设美金到时是7.75
於是便用 7.8-7.75 x 美金結餘
從而產生匯率盈虧
The general exchange rate is just a preset rate, for example: US dollar to Hong Kong dollar is 7.8
And the exchange rate does not need to be changed daily
When issuing an order, user may use the preset exchange rate every time is ok
At year-end, just enter the annual closing exchange rate, and then the system will generate exchange rate gains and losses
For example: at the end of the year, March 31, 2018, assuming that the U.S. dollar is 7.75
So use 7.8-7.75 x USD balance
Resulting in exchange rate gains and losses