Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Starting Out with Programming Logic & Design Second Edition by Tony Gaddis Chapter 10: Files

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 1-2 Chapter Topics 10.1 Introduction to File Input and Output 10.2 Using Loops to Process Files 10.3 Using Files and Arrays 10.4 Processing Records 10.5 Control Break Logic

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output When a program needs to save data for later use, it writes the data in a file and can be used later –In previous programs you wrote, the data was stored in variables –File input and output can interact with various types of applications Word processors Image editors Spreadsheets Games Web browsers

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output Three steps must take place for file interaction 1.Open the file. An output file means creating and preparing it for output; an input file means opening a file and preparing it for reading data from 2.Process the file. Writes data to the file or reads data from the file 3.Close the file. Must be done to disconnect it from the program

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output Types of files include text and binary –A text file contains data that has been encoded as text, using ASCII or Unicode Even numbers in this type of file are stored as text –A binary file contains data that has not been converted to text A text editor is need to view the contents of a binary file

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output Files can be accessed in two methods –Sequential access Data is accessed from the beginning to the end All data must be read –Direct access (aka random access) Any piece of data can be accessed without reading the data that comes before or after it –This chapter will focus on sequential access files

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output Create a file and writing data to it 1.Files that are created should be given a name with an appropriate file extension customers.dat where.dat represents general data 2.Must also create an internal name that is similar to a variable name Declare OutputFile customerFile –OutputFile indicates the mode in which the file will be used –customerFile is the internal name used to work with the file

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output 3. Files must be opened Open customerFile “customers.dat” 4. Data can then be written to a file Write customerFile = “Charles Pace” or Declare String name = “Charles Pace” Write customerFile name 5. Closing a file Close customerFile

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output Delimiters and EOF Marker –A delimiter is a predefined character or set of characters that marks the end of each piece of data It separates the different items stored in a file –An End of File (EOF) marker is a special character or set of characters written to the end of a file It indicates the file’s contents end

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output Reading data from a file 1. An internal variable must first be declared Declare InputFile inventoryFile –InputFile indicates the mode in which the file will be used –inventoryFile is the internal name used to work with the file 2.The file can then be opened –Open inventoryFile “inventory.dat” 3.Data can then be read –Read inventoryFile itemName 4.And finally closed –Close inventoryFile

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Introduction to File Input and Output The append mode –In addition to read and write mode, append mode also exists to add data to a file that also exists –If the file already exists, it will not be erased –If the file does not exist, it will be created –When data is written to the file, it will be written to the end of the file Declare OutputFile AppendMode myFile

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Using Loops to Process Files Loops can be used to enter large amounts of data For counter =1 To numDays Display “Enter the sales for day #”, counter Input sales Write salesFile sales //writes to the file End For Loop could also be used to read large amounts of data While NOT eof(salesFile) Read salesFile sales Display currencyFormat(sales) End While

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Using Files and Arrays Files and arrays can be used together –The contents of an array can be saved to a file Open the file Use a loop to step through each element of the array Write the contents to a file on each iteration –The contents of a file can be read into an array Open the file Use a loop to read each item from the file Store each item in an array element

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Processing Records Data that is stored in a file is frequently organized in records –A record is a complete set of data about an item –A field is a single piece of data within a record Figure Fields in a record

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Processing Records Writing Records –An entire record is done using a single Write statement Write employeeFile name, idNumber, department Reading Records –Done in a similar fashion Read employeeFile name, idNumber, department Algorithms can also be used for adding records to a file, searching for a specific record(s), modifying a record, and/or deleting a record

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Control Break Logic Control break logic interrupts a program’s regular processing to perform a different action when a control variable’s value changes or the variable acquires a specific value –One example is the use of a line counter to pause the program before the information being displayed goes out of view –This can be done with an if statement

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Control Break Logic If lines==24 Then Display “Press any key to continue…” Input Set lines = 0 // resets the counter End If Figure Pausing output after 24 items are displayed

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley End of Chapter Review Multiple Choice questions 1 – 15 pages

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 1 A file that data is written to is known as a(n) a.input file b.output file c.sequential access file d.binary file 1-19

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 1 A file that data is written to is known as a(n) a.input file b.output file c.sequential access file d.binary file 1-20

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 2 A file that data is read from is know as a(n) a.input file b.output file c.sequential access file d.binary file 1-21

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 2 A file that data is read from is know as a(n) a.input file b.output file c.sequential access file d.binary file 1-22

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 3 Before a file can be used by a program, it must be a.formatted b.encrypted c.closed d.opened 1-23

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 3 Before a file can be used by a program, it must be a.formatted b.encrypted c.closed d.opened 1-24

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 4 When a program is finished using a file, it should do this. a.erase the file b.open the file c.close the file d.encrypt the file 1-25

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 4 When a program is finished using a file, it should do this. a.erase the file b.open the file c.close the file d.encrypt the file 1-26

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 5 The contents of this type of file can be viewed in an editor such as Notepad. a.text file b.binary file c.English file d.human-readable file 1-27

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 5 The contents of this type of file can be viewed in an editor such as Notepad. a.text file b.binary file c.English file d.human-readable file 1-28

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 6 This type of file contains data that has not been converted to text. a.text file b.binary file c.Unicode file d.symbolic file 1-29

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 6 This type of file contains data that has not been converted to text. a.text file b.binary file c.Unicode file d.symbolic file 1-30

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 7 When working with this type of file, you access its data from the beginning of the file to the end of the file. a.ordered access b.binary access c.direct access d.sequential access 1-31

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 7 When working with this type of file, you access its data from the beginning of the file to the end of the file. a.ordered access b.binary access c.direct access d.sequential access 1-32

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 8 When working with this type of file, you can jump directly to any piece of data in the file without reading the data that comes before it. a.ordered access b.binary access c.direct access d.sequential access 1-33

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 8 When working with this type of file, you can jump directly to any piece of data in the file without reading the data that comes before it. a.ordered access b.binary access c.direct access d.sequential access 1-34

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 9 This is a small “holding section” in memory that many systems write data to before writing the data to a file. a.buffer b.variable c.virtual file d.temporary file 1-35

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 9 This is a small “holding section” in memory that many systems write data to before writing the data to a file. a.buffer b.variable c.virtual file d.temporary file 1-36

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 10 This is a character or a set of characters that marks the end of a piece of data. a.median value b.delimiter c.boundary marker d.EOF marker 1-37

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 10 This is a character or a set of characters that marks the end of a piece of data. a.median value b.delimiter c.boundary marker d.EOF marker 1-38

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 11 This is a character or set of characters that marks the end of a file. a.median value b.delimiter c.boundary marker d.EOF marker 1-39

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 11 This is a character or set of characters that marks the end of a file. a.median value b.delimiter c.boundary marker d.EOF marker 1-40

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 12 This marks the location of the next item that will be read from a file. a.input position b.delimiter c.pointer d.read position 1-41

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 12 This marks the location of the next item that will be read from a file. a.input position b.delimiter c.pointer d.read position 1-42

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 13 When a file is opened in this mode, data will be written at the end of the file’s existing contents. a.output mode b.append mode c.backup mode d.read-only mode 1-43

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 13 When a file is opened in this mode, data will be written at the end of the file’s existing contents. a.output mode b.append mode c.backup mode d.read-only mode 1-44

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 14 The expression NOT eof(myFile) is equivalent to a.eof(myFile) == True b.eof(myFile) c.eof(myFile) == False d.eof(myFile) <

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 14 The expression NOT eof(myFile) is equivalent to a.eof(myFile) == True b.eof(myFile) c.eof(myFile) == False d.eof(myFile) <

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 15 This is a single piece of data within a record. a.field b.variable c.delimiter d.subrecord 1-47

Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Question 15 This is a single piece of data within a record. a.field b.variable c.delimiter d.subrecord 1-48