A particular value for a variable that is assigned automatically by an operating system and remains in effect unless canceled or overridden by the operator. 缺省，默認某一變量的特定值，由操作系統自動(dòng)指定并持續有效，除非操作者取消它或使它無(wú)效
Establishing a value for a variable or symbol or establishing what the variable represents. 為變量或符號確定一個(gè)值，或者確定此變量代表的內容。
A variable that is given a constant value for a specified application and that may denote the application. 一種為專(zhuān)用應用程序而給定一個(gè)常數值的變量，而且它可以表示該應用程序。
