CS0004: Introduction to Programming

transcript

Problem Solving and Programming Tools

Review Machine Language

Review Machine Language is a system of instructions

and data executed directly by a computer's central processing unit.

Higher-Level Languages

Higher-Level Languages consists of instruction that people can understand.

Event-driven programming

Event-driven programming is a paradigm in which the flow of programs are determined by events.

A program

A program is a collection of instructions.

A program is a collection of instructions. A compiler

A program is a collection of instructions. A compiler is a computer program that

translates high-level language such as VB in Machine Language.

Running a program

Running a program is executing the instructions given a program.

Programming Languages and Problem Solving In this class we will be using Visual Basic, but

there are many things it shares with most programming languages.

Namely, 3 things:

Namely, 3 things: Takes in data

Namely, 3 things: Takes in data Manipulates the data

Namely, 3 things: Takes in data Manipulates the data Produces some information

If you can break a problem down into these steps, you can create a program to solve it.

But do we start writing code as soon as we run into a problem?

Answer: No.

Algorithms vs. Programs An Algorithm is

Algorithms vs. Programs An Algorithm is a step-by-step procedure

devised for the purpose of taking in data and producing the correct output.

A program is the actual implementation of an algorithm in a programming language.

Before writing a program, you must develop an algorithm to solve a problem.

Very Important: It is highly recommended to think about the problem first, then develop an algorithm, then write the program.

Program Development Cycle When Developing a program in both the real

world AND in this class, there are 6 steps:

world AND in this class, there are 6 steps:1) Analyze the problem

world AND in this class, there are 6 steps:1) Analyze the problem2) Plan a solution

world AND in this class, there are 6 steps:1) Analyze the problem2) Plan a solution3) Design an interface

world AND in this class, there are 6 steps:1) Analyze the problem2) Plan a solution3) Design an interface4) Write the code

world AND in this class, there are 6 steps:1) Analyze the problem2) Plan a solution3) Design an interface4) Write the code5) Test and debug

world AND in this class, there are 6 steps:1) Analyze the problem2) Plan a solution3) Design an interface4) Write the code5) Test and debug6) Document the program

world AND in this class, there are 6 steps1) Analyze the problem2) Plan a solution3) Design an interface4) Write the code5) Test and debug6) Document the program7) (Not done in this class) Maintain the program

world AND in this class, there are 6 steps1) Analyze the problem2) Plan a solution3) Design an interface4) Write the code5) Test and debug6) Document the program7) (Not done in this class) Maintain the program To be successful in this class, you must

perform each of these steps.

Analyze the Problem Understand what the problem is and what the

solution should be

solution should be Keep in mind what the End User should be

able to see and do.

able to see and do. User –

able to see and do. User – Anyone who uses the program.

End User –

End User – The person whom the program was designed for him/her to use.

Also keep in mind what the CORRECT solution to the problem is.

This needs to be done before ANY of the following steps can take place.

solution should be Keep in mind what the End User should be able to

see and do. User – Anyone who uses the program.

People have this job in real life: http://en.wikipedia.org/wiki/Software_analyst

solution should be Keep in mind what the End User should be able to

see and do. User – Anyone who uses the program.

People have this job in real life: http://en.wikipedia.org/wiki/Software_analyst

Plan a Solution Once you understand the problem, you can

develop an algorithm.

develop an algorithm. Create precise steps for the entire flow of the

program. Usually in the form of:

program. Usually in the form of: Get Input

program. Usually in the form of: Get Input Validate Input

program. Usually in the form of: Get Input Validate Input Manipulate Input

program. Usually in the form of: Get Input Validate Input Manipulate Input Output Solution

Every detail should be covered in the algorithm.

Every detail should be covered in the algorithm. Consider what is logical and illogical for the

control flow.

Plan a Solution Once you understand the problem, you can develop

an algorithm. Create precise steps for the entire flow of the

Every detail should be covered in the algorithm. Consider what is logical and illogical for the control

flow. Think about what situations can happen in the

problem.

Plan a Solution Once you understand the problem, you can develop an

algorithm. Create precise steps for the entire flow of the program.

Usually in the form of: Get Input Validate Input Manipulate Input Output Solution

Every detail should be covered in the algorithm. Consider what is logical and illogical for the control flow. Think about what situations can happen in the problem. There are many tools programmers use to model the

flow of a program.

Plan a Solution Once you understand the problem, you can develop an

algorithm. Create precise steps for the entire flow of the program.

Usually in the form of: Get Input Validate Input Process Input Output Solution

Every detail should be covered in the algorithm. Consider what is logical and illogical for the control flow. Think about what situations can happen in the problem. There are many tools programmers use to model the flow of a

program. In real-world software projects, this is often done by committee

Design the Interface An interface is how two component interact

with each other.

with each other. User Interface – How the user interact with your

program.

program. Think about how you allow the end user to

interact with you program.

interact with you program. Consider how the user inputs data and views

results.

results. Think about what makes sense to the end

user. Visual Basic is good for this.

user. Visual Basic is good for this. For this course, this includes windows,

buttons, text boxes, etc.

Design the Interface An interface is how two component interact with each

other. User Interface – How the user interact with your program.

Think about how you allow the end user to interact with you program.

Consider how the user inputs data and views results. Think about what makes sense to the end user. Visual Basic is good for this. For this course, this includes windows, buttons, text

boxes, etc. Again, this is a job in real life: http://

en.wikipedia.org/wiki/User_interface_design

Write the Code Writing code is a process of translating the

algorithm you developed into a programming language.

Coding – technical word for writing code.

Coding – technical word for writing code. This is where knowledge of a programming

language (VB in our case) is used.

Coding – technical word for writing code. This is where knowledge of a programming

language (VB in our case) is used. Again, this is a real-world job: http://

en.wikipedia.org/wiki/Software_developer http://en.wikipedia.org/wiki/Software_engineer

Testing and Debugging Bug -

Testing and Debugging Bug - an error, flaw, mistake, failure, or fault in

a computer program Even experienced software engineers make

mistakes, so it is important to test your program for errors.

Two Kinds (of many) of Errors:

Two Kinds (of many) of Errors: Syntax Error – Error in typing the program.

Two Kinds (of many) of Errors: Syntax Error – Error in typing the program. Logical Error – Inconsistency between what you

want the program to do and what it actually does.

Two Kinds (of many) of Errors: Syntax Error – Error in typing the program. Logical Error – Inconsistency between what you

want the program to do and what it actually does. It’s important to consider all normal and

abnormal inputs for the program.

Testing and Debugging Bug - an error, flaw, mistake, failure, or fault in a

computer program Even experienced software engineers make

Two Kinds (of many) of Errors: Syntax Error – Error in typing the program. Logical Error – Inconsistency between what you want the

program to do and what it actually does. It’s important to consider all normal and abnormal

inputs for the program. Actual Job: http://

en.wikipedia.org/wiki/Software_tester

Complete the Documentation Documentation – Organizing all the material

that describes the program.

that describes the program. Documentation includes:

Comments inside of the code document that describes to whoever reads it what specific sections do.

Comments inside of the code that describe the who the author is, when it was written, and any other relevant information

In commercial settings (industry) this includes user manuals that describe how to use the program.

Complete the Documentation Documentation – Organizing all the material that

describes the program. Documentation includes:

This may seem annoying, but it is a very important requirement for this course.

Complete the Documentation Documentation – Organizing all the material that

describes the program. Documentation includes:

This may seem annoying, but it is a very important requirement for this course.

It is easiest to document code WHILE writing it, as well as completing it once finished writing code.

Modeling Tools To help understand the steps of an algorithm,

programmers use a variety of tools.

programmers use a variety of tools to model the algorithm.

Three that will help us in this class are:

programmers use a variety of tools Three that will help us in this class are:

Flowcharts – Graphically depict the logical steps to carry out a task and show how the steps relate to each other

Pseudocode – English-like phrases with some Visual Basic terms to outline the task

Hierarchy Charts – Show how the different parts of a program relate to each other.

Developing an Algorithm Consider the problem of finding out how many

stamps you need to put on an envelope to mail it.

The rule here is that you need 1 stamp for every 5 sheets of paper in the envelope.

So the algorithm looks something like this:

So the algorithm looks something like this:1. Get the number of sheets from the user.

So the algorithm looks something like this:1. Get the number of sheets from the user.2. Divide the number of sheets by 5

So the algorithm looks something like this:1. Get the number of sheets from the user.2. Divide the number of sheets by 53. Round the result from step 2 the highest

whole number

So the algorithm looks something like this:1. Get the number of sheets from the user.2. Divide the number of sheets by 53. Round the result from step 2 the highest

whole number4. Output the number of stamps

stamps you need to put on an envelope to mail it. The rule here is that you need 1 stamp for every 5

sheets of paper in the envelope. So the algorithm looks something like this:1. Get the number of sheets from the user.2. Divide the number of sheets by 53. Round the result from step 2 the highest whole

number4. Output the number of stamps Let’s see how the three modeling tools work here

sheets of paper in the envelope. So the algorithm looks something like this:1. Get the number of sheets from the user.2. Divide the number of sheets by 53. Round the result from step 2 the highest whole

number4. Output the number of stamps Let’s see how the three modeling tools work here

sheets of paper in the envelope. So the algorithm looks something like this:1. Get the number of sheets from the user. (Input)2. Divide the number of sheets by 5 (Process)3. Round the result from step 2 the highest whole

number (Process)4. Output the number of stamps (Output) Let’s see how the three modeling tools work here

Developing an Algorithm So a specific example looks like

Developing an Algorithm So a specific example looks like 1. The user inputs 16 sheets of paper

Developing an Algorithm So a specific example looks like 1. The user inputs 16 sheets of paper2. Dividing 16 by 5 results in 3.2

Developing an Algorithm So a specific example looks like 1. The user inputs 16 sheets of paper2. Dividing 16 by 5 results in 3.23. Rounding 3.2 up results in 4

Developing an Algorithm So a specific example looks like 1. The user inputs 16 sheets of paper2. Dividing 16 by 5 results in 3.23. Rounding 3.2 up results in 44. Output 4 stamps

Developing an Algorithm So a specific example looks like 1. The user inputs 16 sheets of paper2. Dividing 16 by 5 results in 3.23. Rounding 3.2 up results in 44. Output 4 stamps Simple enough, right? What could go

wrong?

Developing an Algorithm So a specific example looks like 1. The user inputs 16 sheets of paper2. Dividing 16 by 5 results in 3.23. Rounding 3.2 up results in 44. Output 4 stamps Simple enough, right? What could go

wrong? What if the user inputs “Banana” sheets of

paper?

Developing an Algorithm Revised Algorithm:1. Get the number of sheets from the user.

(Input)

(Input)2. Check to see if the input is a positive

number. (Validate)

number. (Validate)3. Divide the number of sheets by 5 (Process)4. Round the result from step 2 the highest

whole number (Process)5. Output the number of stamps (Output) Now that our algorithm is set, lets see how

the modeling tools work.

number. (Validate)3. Divide the number of sheets by 5 (Process)

whole number (Process)

whole number (Process)5. Output the number of stamps (Output)

whole number (Process)5. Output the number of stamps (Output) Now that our algorithm is set, lets see how

the modeling tools work.

Hierarchy ChartsPostage Stamp Program

Read Sheets Calculate Stamps Display Stamps

Getsheets

Make suresheets is

a positive integer.

Getsheets

Make suresheets is

a positive integer.

Must benumber

Must bepositive

Must be

integer

Getsheets

Make suresheets is

a positive integer.

Set stamps =sheets / 5

Round stampsup to next whole

number

Must benumber

Must bepositive

Must be

integer

Getsheets

Make suresheets is

a positive integer.

Display:"You will need: "

# of stampsSet stamps =sheets / 5

Round stampsup to next whole

number

Must benumber

Must bepositive

Must be

integer

Hierarchy Charts Good for showing the structure of the

algorithm

algorithm Good at breaking down the algorithm into

components

components Not too great at showing the order of events

components Not too great at showing the order of events Flow Charts are better at showing the order in

which the components execute.

Flow Charts Components

Flow Charts Components Flow Line - indicates the flow of logic

Terminal – indicates the start or end of a task

Flow Charts Components Flow Line - indicates the flow of logic

Terminal – indicates the start or end of a task

Input/Output – used for input or output operations. What is to be input or output should be in the figure.

Flow Charts Processing - used to show a processing step.

The instructions are displayed in the figure.

Decision – used to show when a decision needs to be made. Lines for yes and no come out of it. The question is displayed in the figure.

Connector – Used to join flow lines.

Flow ChartsStart

Read sheet

Flow ChartsStart

Read sheet

sIs sheets positiv

e numbe

Flow ChartsStart

Set stamps = sheets / 5

Read sheet

sIs sheets positiv

e numbe

Flow ChartsStart

Read sheet

sIs sheets positiv

e numbe

Round stamps up

to next whole

number

Flow ChartsStart

Read sheet

sIs sheets positiv

e numbe

Round stamps up

to next whole

numberDisplay: "You will need: " #stamps

Flow ChartsStart

Read sheet

sIs sheets positiv

e numbe

Round stamps up

to next whole

Flow ChartsStart

Read sheet

sIs sheets positiv

e numbe

Round stamps up

to next whole

Display error

message

Flow ChartsStart

Read sheet

sIs sheets positiv

e numbe

Round stamps up

to next whole

Display error

message

Pseudocode This will become more clear when you

understand VB terms better.

understand VB terms better. Pseudocode is good for listing the steps of an

algorithm in a form that is easier to translate into VB.

understand VB terms better. Pseudocode is good for listing the steps of an

algorithm in a form that is easier to translate into VB.

Important: There is NO SPECIFIC FORM to pseudocode, it can look as much like VB or English as you want. The more VB you learn, the more VB-like pseudocode you can write.

PseudocodeProgram: Determine the proper number of

steps for a letterRead sheetsif sheets is a positive integer

Stamps = Sheets/5Whole Stamps = Stamps rounded to next whole numberOutput Whole Stamps

elseDisplay Error

CS0004: Introduction to Programming

Documents