COP1006 1

Planning for the Solution

Lesson 3

McManus

COP1006 2

Computers are Dumb!

• You have to tell them – what to do– what to use– in what order to do it and– what to do if your user

does not do what you want them to do!

McManus

COP1006 3

Solutions

• Don’t reinvent the wheel!• Use solutions that have been

– already proven successful – been created just to be reused

McManus

COP1006 4

Solution Trade Offs

• Speed• Readability• Understandability• Maintainability• Reusability

McManus

We take these into consideration every time we create a program.

COP1006 5

How the Computer Stores Data

• Files– Program – set of instructions– Data – raw pieces of facts

McManus

database

records

Data (fields)

files

COP1006 6

Hierarchy of a DBMS

McManus

DBMS

Database Management Systemmade up of one or more databases

DB

A databasemade up of one or more tables, queries, forms, reports, etc

Tableinformation related to one topicmade up of one or more records Rooms Instructors

Record

information related to one specific entitymade up of one or more fields Inventory Classes

Field

information related to one specific part of an entitymade up of one particular data type

Item NameItem Number

Student NameStudent ID

NWF State College

FWB

ExampleDefinition

COP1006 7

Terminology

• Semantics– The concept or idea of the item– Ex. The numeral three is an idea that

humans have established representing the concept of three items

• Syntax– The physical/visible representation of

the idea – Ex. “three” “3”

McManus

COP1006 8

Organizing the Problem

• Tools– Algorithms– Problem Analysis Chart (PAC)– Structure/Interactivity Charts– Input Processing Output (IPO) Chart– Flowcharts– Hierarchy Charts

• But…first we have to understand the Software Life Cycle

McManus

COP1006 9

Software Life Cycle

McManus

Problem Definition

Software & Architectural DesignSystemRequirements Detailed Design

SpecificationsDesign Validation

Coding*Testing/

AcceptanceOperations/

Maintenance

Indicates= reiterative steps after testing and verification of each phase

*Implementation

The Waterfall Model

COP1006 10

Analyzing the Problem

• Understand the Problem• Analyze the Requirements of the

Problem• Figure out what will be the outcome

Very often we’re not given the inputs to a problem, only the desired output.

McManus

COP1006 11

PAC Payroll Example

Given Data Required ResultsHoursPayRate

Gross Pay

Processing Required Solution AlternativesGrossPay = Hours * PayRate Define the Hours Worked and Pay

Rate as constantsDefine the Hours Worked and Pay Rate as variablesDefined the Hours Worked and Pay Rate as input values

McManus

COP1006 12

Structure Charts

McManus

Calculate Gross Pay

ObtainInput Values

Calculate Gross Pay

Print Pay Check

PR

HRS PR

HRSGP

GP

*Includes data flow

COP1006 13

Interactivity Charts

McManus

Calculate Gross Pay

ObtainInput Values

Calculate Gross Pay

Print Pay Check

*Includes data flow

Hourly Rate

Hours Worked

COP1006 14

Input Processing Output (IPO)

Input Processing Output

Hours WorkedPay Rate

1. Enter Hours Worked

2. Enter Pay Rate

3. Calculate Pay

4. Print Pay

Gross Pay (the pay check)

McManus

COP1006 15

Flowchart

• Originally used to describe the entire program.

• Now, used to define – selection (decision) and – repetition (looping) structures

McManus

COP1006 16

Flowchart Symbols

• Flowlines– used when direction is in doubt

• Start/(End/Stop/Exit)• Processing• I(input)/O(output)• Decision

McManus

Begin End

Calculate Gross Pay

Print Pay Check

MoreEmployees?

COP1006 17

Example Flowchart

McManus

Snoozeor Off?

Alarm goes off!

Sleep or Get up?

Zzzzz!

Snooze

Sleep

Get Dressed. . .

Snooze= 9?

< 9

Ignore Alarm, Forget Boss,

Forget Instructor – Probably creating a problem?

COP1006 18

Pseudocode

• Everything is included, but written in English rather than any one language’s syntax

• Useful for debugging• Ex.

McManus

Obtain PayRateObtain HoursWorkedGrossPay equals PayRate Multiplied by HoursWorkedPrint GrossPay

COP1006 19

Documentation

• Internal• External

• Written in different language styles

McManus

COP1006 20

Internal Documentation

• Used to explain what is being done (and why) within the program

• Most often takes the form of comments within the program– Written in Language that Programmer,

not user, will understand

McManus

' Insert a new node in the binary search tree.

' If the root node is null, create the root node here.

' Otherwise, call the insert procedure of class TreeNo

COP1006 21

External Documentation

• Manuals or Help menus to assist the user– Includes

• User Manuals• System Manuals

• User must be able to understand…

McManus

Make text bold

1. Select the text you want to change.

2. Click Bold on the Formatting Toolbar.

COP1006 22

Debugging the Solution

• Walkthroughs– Walking through the process to verify

that the solution • is solving the right problem and • works correctly

– You can use any of the charts or Pseudocode for this step

• Helps find bugs

McManus

COP1006 23

Coding

• After determining that the solution is correct

• Select the appropriate language• Code the program

McManus

COP1006 24

Testing

• Test the coded solution• Best done by someone other than

the programmer

McManus

COP1006 25

60% to 70% of all Faults

• found in large-scale software projects are specification and design faults.

• Where do most of these faults originate?– Not fully understanding the problem and – then creating a specification based on an

erroneous problem definition.• Industry’s high priority

– involves the development and use of techniques that will help find faults during the earliest phases.

McManus

COP1006 26

Where to Place the Blame?

• Nowhere!It is not the

purpose to place blame when a fault is found…

Only to fix the fault!

McManus

COP1006 27

With team development…

• new problems arise, such as:– different styles of writing code, – interface difficulties, – different declared types (integer vs real)– different understandings of the problem caused

by communication problems, and – even something as simple as the order in

which variables are listed within a procedure’s call statement.

McManus

COP1006 28McManus

Next?