在以BUFFER为首址的内存中存放了若干个带符号数， 其个数存放在首单元，寻找出它们最大值放到存储单元MAXVAL中， 最小值放到存储单元MINVAL中。-BUFFER headed to the site in memory storage of a number of a signed, the number stored in the first unit, find out their storage unit MAXVAL put in the maximum, minimum, put in the storage unit MINVAL.