Programming Logic and Design. Chapter 7. File Handling and Applications

Objectives

In this chapter, you will learn about:
Computer files
The data hierarchy
Performing file

Understanding Computer Files

Computer file
A collection of data stored on permanent storage

Understanding Computer Files (continued)

Organizing files
Directories and folders
Organization units on storage devices
Path
Combination

Understanding the Data Hierarchy

Data hierarchy
Describes the relationships between data components
Consists of:

Performing File Operations

Use data files in your programs
Declaring a file
InputFile employeeData
OutputFile

Performing File Operations (continued)

Programming Logic and Design, Seventh Edition

Figure 7-2 Reading

Performing File Operations (continued)

Writing data to a file
output name, address, payRate

Figure 7-3 Flowchart and pseudocode for a program that uses files

Programming

Figure 7-3 Flowchart and pseudocode for a program that uses files

A Program that Performs File Operations

Backup file
A copy that is

Understanding Sequential Files and Control Break Logic

Sequential file
Records are stored one

Understanding Sequential Files and Control Break Logic (continued)

Programming Logic and Design,

Understanding Sequential Files and Control Break Logic (continued)

Programming Logic and Design,

Understanding Sequential Files and Control Break Logic (continued)

Single-level control break
A detour

Programming Logic and Design, Seventh Edition

Figure 7-5 Mainline logic and getReady()

Programming Logic and Design, Seventh Edition

Figure 7-6 The produceReport() and controlBreak()

Programming Logic and Design, Seventh Edition

Figure 7-7 The finishUp()module for the

Merging Sequential Files

Merging files
Combining two or more files while maintaining the

Merging Sequential Files (continued)

Two conditions required for merging files
Each file has

Merging Sequential Files (continued)

Figure 7-8 Sample data contained in two customer

Mainline logic similar to other file-processing programs, except for handling two

Programming Logic and Design, Seventh Edition

Figure 7-10 Mainline logic of a

Programming Logic and Design, Seventh Edition

Figure 7-12 Start of merging process

Programming Logic and Design, Seventh Edition

Figure 7-13 Continuation of merging process

Master and Transaction File Processing

Some related files have a master-transaction relationship

Master and Transaction File Processing (continued)

Examples
A library maintains a master file

Master and Transaction File Processing (continued)

Updating approaches
Change information in master file
Copy

Figure 7-16 The housekeeping() module for the master-transaction program, and the

Figure 7-17 The updateRecords() module for the master-transaction program

Programming Logic and

Master and Transaction File Processing (continued)

Programming Logic and Design, Seventh Edition

Figure

Random Access Files

Batch processing
Involves performing the same tasks with many records,

Random Access Files (continued)

Random access files
Records can be located in any

Summary

Computer file
A collection of data stored on a nonvolatile device in