Chapter17–FilesandStreams.ppt

Chapter 17 – Files and Streams 17.1 Introduction Variables and arrays only temporary Lost during garbage collection or when a program terminates Files used for long term storage Called persistent data This chapter deals with: Sequential-access files Random-access files File processing features Stream-input/output features 17.2 Data Hierarchy Data Hierarchy: Gets more complex as you move along: Bit: either one or zero All data represented as combination of bits Easy for electronic devices to understand Byte: eight bits Character: in C# two bytes Character set: set of all characters used to program and represent data on a particular computer Field: composition of characters that convey a meaning Record: composition of several, related fields File: group of related records Record key: identifies record to a particular entity Sequential file: records stored in order of record-key 17.2 Data Hierarchy 17.3 Files and Streams Files are sequential streams of bytes Ends with either an end-of-file marker or a specific byte When file opened C#: Creates an object Associates a stream with that object Three stream objects: Console.In: returns standard input stream object Console.Out: returns standard output stream object Console.Error: returns standard error stream object Namespace System.IO needed for file processing 17.3 Files and Streams BinaryFormatter: used to serialize and deserialize objects Serialize:converting an object into a format that can be written to a file without losing data Deserialize: Reading formatted text from a file and reconstructing the original object from it System.IO.Stream: allows representation of stream as bits FileStream: read to and write from sequential-access and random-access files MemoryStream:transfer of data directly to and from memory BufferedStream: uses buffer to transfer to memory 17.3 Files and Streams 17.4 Classes File and Directory Information stored in files Files organized in directories Directory class used to manipulate directori