1. Understanding the Mainline Logical Flow Through a Program (continued)
Procedural program: one procedure follows another from beginning to end
Mainline logic has three distinct parts:
Housekeeping: steps to get ready
Main loop: instructions executed for every input record
End-of-job: steps taken at end of program
Break the logic down into at least three modules
Programming Logic and Design, Introductory, Fourth Edition

2. Understanding the Mainline Logical Flow Through a Program (continued)
Programming Logic and Design, Introductory, Fourth Edition

3. Understanding the Mainline Logical Flow Through a Program (continued)
Modularization of the program:
Keeps the job manageable
Allows multiple programmers to work simultaneously
Keeps the program structured
Programming Logic and Design, Introductory, Fourth Edition

4. Housekeeping Tasks
Housekeeping tasks: include all steps that occur at the beginning of the program
Declare variables
Open files
Perform one-time-only tasks such as printing headings
Read the first input record
Programming Logic and Design, Introductory, Fourth Edition

5. Declaring Variables Assign identifiers to memory locations
Specify the name and data type
Use meaningful names and follow standards
Prefixes may be used to group related variables
Declare a variable for each field in a data file
Programming Logic and Design, Introductory, Fourth Edition

6. Declaring Variables (continued)
Initializing (or defining) the variable: providing an initial value
Some languages provide default initial values
Other languages leave variables with an unknown or garbage value
Variables representing data fields in files do not need to be initialized
Programming Logic and Design, Introductory, Fourth Edition

7. Declaring Variables (continued)
Can use variables for report headings
Embed any required spaces
Heading can be printed using these variables
Programming Logic and Design, Introductory, Fourth Edition

8. Declaring Variables (continued)
Local variables: declared within a module
Global variables: declared at the beginning of the program, and used in all modules
Annotation box: flowchart symbol containing notes
Data Dictionary: list of variables used in a program, with their type, size, and description
Programming Logic and Design, Introductory, Fourth Edition

9. Opening Files Specify file name and path (location)
Issue a file open command
If no input file is opened, input may be accepted from the standard input device (e.g., keyboard)
You must open both input and output files to be used, including printer output device
If no output file is opened, standard output device (e.g., monitor) may be used
Programming Logic and Design, Introductory, Fourth Edition

10. Printing Headings
Printing headings for reports usually is done at beginning of the program or possibly for each new page
Programming Logic and Design, Introductory, Fourth Edition

11. Reading an Input Record
Reading the first input record is the last housekeeping task
Interactive application:
Interacts with users via keyboard or mouse input
Program pauses when the read command is executed until the user enters data
Delimiter: a character designated as a separator between data values
Prompt: an output statement that asks the user to enter specific data
Programming Logic and Design, Introductory, Fourth Edition

12. Reading the First Input Record (continued)
Interactive input: (from a keyboard)
Programming Logic and Design, Introductory, Fourth Edition

13. Reading an Input Record
Input from a data file:
Programming Logic and Design, Introductory, Fourth Edition

14. Checking for the End of the File
After reading a file
For an interactive program, EOF may be determined when:
User enters a predetermined sentinel value
User selects a screen option using a mouse
For input from a file, the input device recognizes EOF
EOF may occur on the first read
If there is data, each record is processed before the next read occurs
Programming Logic and Design, Introductory, Fourth Edition

15. Checking for End of File (continued)
Programming Logic and Design, Introductory, Fourth Edition

16. Modules, Subroutines, Procedures, Functions, or Methods
Unit of code that performs one small task
Called a subroutine, procedure, function, or method
Modularization: breaking a large program into modules
Programming Logic and Design, Introductory, Fourth Edition

17. Modules, Subroutines, Procedures, Functions, or Methods (continued)
Advantages of modularization:
Provides abstraction
Allows multiple programmers to work simultaneously
Allows code reuse
Makes identifying structures easier
Programming Logic and Design, Introductory, Fourth Edition

18. Modularization Provides Abstraction
Focusing on important properties while ignoring non-essential details
Avoids the low-level details and uses a high-level approach
Makes complex tasks look simple
Programming Logic and Design, Introductory, Fourth Edition

19. Modularization Provides Abstraction (continued)
A To-Do list
with abstraction: without abstraction:
Programming Logic and Design, Introductory, Fourth Edition

20. Modularization Allows Multiple Programmers to Work on a Problem
Large programming projects can be divided into modules
Modules can be written by different programmers
Development time is significantly reduced
Programming Logic and Design, Introductory, Fourth Edition

21. Modularization Allows You to Reuse Your Work
Reusability: the ability to use modules in a variety of applications
Reliability: assurance that a module has been tested and proven to function correctly
Programming Logic and Design, Introductory, Fourth Edition

22. Modularizing a Program
Most programs contain a main module
Contains the mainline logic
Accesses other modules or subroutines
Rules for module names used here:
Must be one word
Should be meaningful
Are followed by a set of parentheses
Programming Logic and Design, Introductory, Fourth Edition

23. Modularizing a Program (continued)
Calling program (or calling module): one that uses another module
Flowchart symbol for calling a module: a rectangle with bar across the top
Flowchart for the module contains:
Module name in the start symbol
exit or return in the stop symbol
When a module is called, logic transfers to the model
When module ends, logic transfers back to the caller
Programming Logic and Design, Introductory, Fourth Edition

24. Modularizing a Program (continued)
Programming Logic and Design, Introductory, Fourth Edition

25. Modules Calling Other Modules
Programming Logic and Design, Introductory, Fourth Edition

26. Understanding Documentation
All supporting material that goes with a program
Two major categories: for users and for programmers
Usually created by system analysts and/or tech writers
May be printed or electronic (Web or CD)
End users: people who use computer programs
Program Documentation:
Internal program documentation: comments within code
External program documentation: supporting paperwork written before programming begins
Programming Logic and Design, Introductory, Fourth Edition

27. Completing the Documentation
Program documentation may contain:
Output design
Input description
Flowcharts
Pseudocode
Program code listing
User documentation may contain
Manuals
Instructional material
Operating instructions
Programming Logic and Design, Introductory, Fourth Edition