7 steps to program development

1. Understand the problem

2. Plan the logic

3. Code

4. Translate to machine language

5. Test

6. Production

7. Maintenance

Errors with increasing severity

Syntax errors

-compiler error

Runtime errors

-abnormal ending to a program, (abend)

Logic errors

Hierarchy of data

Character D

Field Dave

Record Dave Larkins

File Group of records

Properties of Variables

Memory location (for the computer)

Identifier (for the human)

Data type (characters, #s, String)

Value

Declare a variable

creates the variable in blanks or unused space (GRABBING) name and type

Initializing a variable

empty a space for a variable and claims it for the program

Assignment operator

inserts a value into a variable for use

Java, Count = 7

Programming Structures-

sequence

selection

interation

If, Then, Else- Selections or Decisions

Single Alternative If ( Unary)

in only one situation or category

-negative is when If = False

Ex: If x /= 3

Then (True)

End If

Only one side requires extra work

Dual Alternative If ( Binary)

Yes or No….2 branches or possibilities

Ex:

If x = = 3

Then (True)

Else (continue)

Doing extra work both ways

Structures

Clarity

Efficiency

Professionalism

Modularity

Abstraction

provides a big picture view

Functional cohesion

Documentation

All supporting material that goes with a program.

Internal Documentation

Comments- non executing statements stuck in code

-purpose, writer, last day compiled, assumptions, declare variables

-comments per paragragh

-comments for unique commands

User Documentation

Instructions, manuals

Output Documentation

creens, print layout, print chart, report requirements

Input Documentation

what data is available, and requirements, security>entry screen

Mainline logic

base program (traffic director)

-Controls the termination of the program

-90% of processes

-File Processing- reading records from a file

-GUI based user interaction

*EOF (End of File indicator)

at the end of a file, often used to cue mainline logic to terminated command or the end of a program

Housekeeping Module

runs once before opening the file, eof?, formats reports, opens files

Processing Module

Guts of the program

Finish up Module

runs at the end of the program, closes the file

Priming Read

read the first record, done in Housekeeping

Case Structures

Compound Selections

If … and/or …

-eliminates more than 1 variable

Not/or Condition (!=….or….) – always answers true

Case (switch) structure

suited for decisions for a single variable

Looping (iteration)

Main loop, Mainline logic- creates a set of instructions and lets us run them over and over again, and end program

Pretest Loop

ask question and process

Posttest Loop

process then ask question

"do...while"

For Loop

lways pretest, finite loop

Finite loop-set to execute a set # of times

Rolling Total

totals updated as data input, saves steps

Hard Edits

stop users in tracks

Soft Edits

suggest may be wrong

Validation

-data type

-data range

-reasonability

-presence of data

Exception handling-

the bulk of programming is there to validate functioning

File merging

Merges files that are sorted the same

-new files are added to a “transaction file” and merged nightly

Scope

ModuleCall

ModuleCall(argument, variable, parameter)

Argument/parameter list

Number of variables

Correct datatype

Correct order

Module coupling

Loose…data coupling

Control coupling

Pathological coupling

Cohesion

Functional Cohesion is best

Polymorphism

object can change its output based on the context it is used. Example: delete key.

-4 different methods, all with the same name. The calling module can know which one to use

Overloading

a method that solves the same problem, but with different arguments, and varying order

Methods

Usually public

Attributes

Characteristics (height, W, letters, etc. color)

-public and private (generally private)

Constructor method

creates instance

Destructor method

dissolves instances when object goes out of scope.

Client

uses a class object, instantiates object

One partner designs the program.

The other codes.