Before defining the specifies of the data type and data structures,let us first define a term that will be used throughout this text. A data value is a piece of a data that we consider, perhaps only momenarily ,as a single entity. We might consider, for example the integer value 593 as a single data value.
The set { 32.99,-1.04,0.396} might be considerd in its entirety a single data value. It might also be considered to be composed of three distinct component values that are somehow related. In this case, theri relationships to each other are that they are members of the same set. If we decompose a data value as we have done with the set value, we need term for the pieces that result.Each piece is a value fo another data type in this case real. We will call these component values component elements, or simply elements.
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在定義數據數據結構和數據類型的一些特點之前,先讓我們來定義在全文中都要用到的一些術語. 數據值:一個數據值就是一個可以暫時看作是單獨的整體的一個數據段,例如,我們可以把整數593看作上單獨的數據值.
集合{3299,01,04,0.396} 可以看作上從整體上看可以看作是一個單獨的數據值.當然,他也可以看作是三個以莫種關係相關聯的不同的部分成.在這個例子中,他們之間的關係就是是同一個集合的成員.假如我們象分解一個集合的值來分解一個數據值的話,我們必須定義一個術語來描述結果的數據段. 每個數據段就是另一個數據類型的值(這個例子就是real型).我們稱這些組成部分爲組成元素,簡稱元素.