这是一个自动售货机程序实现，功能如下：1.按一下button1按钮，表示购买货物A，第一个LED灯亮；按两下button1按钮，表示购买货物B，第二个LED灯亮；按三下button1按钮，表示购买货物C，第三个LED灯亮，同时7段数码管显示所要购买货物的价格。

2.LED灯亮后，开始输入硬币。button2按一下，输入10元，按两下，输入二十元，以此类推；Button3按一下输入5元，按两下输入10元，以此类推；button4按一下输入1元，按两下输入2元，以此类推。7段数码管显示已投入的总钱数，再次按下button1键，7段数码管显示找零数目，同时指示货物的LED灯熄灭。

3.如果投入的钱币不够就按下button1键确认购买，数码管显示“ER”。（vga显示部分有缺陷）-This is a vending machine program implementation, the following functions: 1 Click button1 button to indicate that buy goods A, the first LED lights　double-click button1 button to indicate that buy goods B, the second LED lights　press three times. button1 button to indicate that buy goods C, the third LED lights, while the 7-segment LED display prices of goods to be purchased. After 2.LED lights, start typing coins. button2 Click, enter $ 10, double-click, enter $ 20 and so on　Button3 press the Enter 5 yuan, twice for $ 10, and so on　button4 Click Enter $ 1, twice for 2 yuan, and so on. 7-segment display of the total number of money has been invested, press button1 button again, 7-segment display the change number, while indicating the goods LED light goes out. 3. If the money is not enough to put the press button1 button to confirm the purchase, digital display " ER" .