《计算机科学导论》课件Unit 11Data and File Structure培训资料.pptVIP

Sequential files Records in a sequential file【顺序文件】 can only be read and written in sequence. To access a specific record within the file, the program must successively retrieve the previous records. An EOF (end-of-file) marker is put after the last record. Sequential files are useful in applications which need to access all records in sequence from beginning to end. For example, if personal information about each employee in a company is stored in a file, you can use sequential access【顺序访问】 to retrieve each record at the end of month to print the paychecks. In this case, sequential access is more efficient and easier than random access【随机访问】. However, indexed files are very inefficient for random access of large data files * 11-1 Abstract Data Types 11-2 List 11-3 Stack 11-4 Queue 11-5 Tree and Graph 11-6 File Structure 11-7 References And Recommended Reading 11-8 Summary 11-9 Practice Set OUTLINE * Understand the most common data structures. Understand how to organize records in a file? After reading this chapter, you are supposed tobe able to : OBJECTIVES Have a knowledge of the most commonly used collision resolution methods. Understand how to add or delete data from a specific data structure? * 11-1 Abstract Data Types A data type is composed of a type and a collection of operations to manipulate the type. The realization of a data type is an abstract data type (ADT) 【抽象数据类型】, which is a software component. The interface of an ADT is defined according to a type and a set of operations on that type. While its inputs and outputs determine the behavior of each operation. An ADT does not specify how to implement the data type. The hiding of implementation details from the user and protecting it from outside access is referred to as encapsulation【封装】. The concept of ADT is an instance of managing complexity through abstraction. Complexity and its handling techniques are a central theme of computer science. 11-1 Abstract Data Types When dealing