REPETITION (IN EVERYDAY LIFE)

COPYRIGHT 2010: Dr. David Scanlan, CSUS

REPETITION(IN EVERYDAY LIFE)

COPYRIGHT 2010: Dr. David Scanlan, CSUS CONTROL STRUCTURES

OBJECTIVES

• To FULLY understand the following control structures:•REPEPITION•SELECTION (To be covered in another set of slices.) SEQUENCE (To be covered in another set of slices.)

• To see how control structures are used every second in our daily lives.

• To understand that a FULL comprehension of these control structures is the KEY to problem solving when writing computer programs.

IMPORTANT: You MUST learn these control structures PERFECTLY in order to succeed in this course. These are the most important concepts the course.


Three Control Structures:1. Repetition (Also called Iteration or Looping)

• DO-WHILE• DO-UNTIL

2. Selection (Also called Decision)

• IF-THEN-ELSE• CASE

3. Sequence

CONTROL STRUCTURES

IMPORTANT: You MUST learn these control structures PERFECTLY in order to succeed in this course. You can't solve computer programming problems without control structures. These are the most important concepts the course. Do this throughout the course.

COPYRIGHT 2010: Dr. David Scanlan, CSUS REPETITION (DOWHILE) IN EVERYDAY LIFE

DOWHILE examples

I smile WHILE I

am happy.

I yell WHILE I am mad.

I sleep WHILE I am tired.

I rest WHILE I am sick.

We listen WHILE the boss is talking.

Everyday Life:• Every second, we are engaged in one or more control structures.• DOWHILE

• DO something WHILE a certain condition is TRUE.• All MIS 15 students MUST identify 25 situations where they are using

the DOWHILE control structure in their everyday life before the next class. Do this throughout the course.

COPYRIGHT 2010: Dr. David Scanlan, CSUS REPETITION (DOWHILE) IN EVERYDAY LIFE

WHILE time is less than 5:00 pm,

continue working.

DOWHILE CONTROL STRUCTURE• DO the loop WHILE the condition is TRUE.• With pretest:

• Condition is tested BEFORE the body of the loop is executed.

• With posttest:• Condition is tested AFTER the body of

the loop is executed.• The red symbols and lines make up the

D0WHILE control structure below.• In Visual Basic.NET there is a loop called

DOWHILE and it functions exactly as this one..

STARTPROGRAM

Increment Clock

TRUE

FALSE

EXITPROGRAM

Do WhileClock < 5:00 pm

Set Clock = 8:00 am

DOWHILE Loop

Body of the Loop

Condition Pretest

COPYRIGHT 2010: Dr. David Scanlan, CSUS REPETITION (DOUNTIL) IN EVERYDAY LIFE

DOUNTIL examples

I smile UNTIL I am sad.

I yell UNTIL I

am calm.

I sleep UNTIL I am

rested.

I rest UNTIL I am well.

We listen UNTIL the boss is silent.

Everyday Life:• Every second, we are engaged in one or more control structures.• DOUNTIL

• DO something UNTIL a certain condition is TRUE.• All MIS 15 students MUST identify 25 situations where they are using

the DOUNTIL control structure in their everyday before the next class.

COPYRIGHT 2010: Dr. David Scanlan, CSUS REPETITION (DOUNTIL) IN EVERYDAY LIFE

More DOUNTIL examples

I work UNTIL

5:00 pm

I cook UNTIL the food is done

I work UNTIL

the house is finished.


STARTPROGRAM

Increment Clock

FALSE

TRUE

EXITPROGRAM

Do UntilClock = 5:00 pm

Set Clock = 8:00 am

REPETITION (DOUNTIL) IN EVERYDAY LIFE

DOUNTIL CONTROL STRUCTURE• DO the loop UNTIL the condition is TRUE.• With pretest:

• Condition is tested BEFORE the body of the loop is executed.

• With posttest:• Condition is tested AFTER the body of

the loop is executed.• The red symbols and lines make up the

D0UNTIL control structure below.• In Visual Basic.NET there is a loop called

DOUNTIL and it functions exactly as this one..

DOUNTIL Loop

Body of the Loop

Condition Pretest

I work UNTIL

5:00 pm

COPYRIGHT 2010: Dr. David Scanlan, CSUS REPETITION (DOWHILE vs. DOUNTIL)

Figs_1-140

STARTPROGRAM

ProgrammingStatements

EXITPROGRAM

Test theCondition

Initialize theCondition

STARTPROGRAM


EXITPROGRAM

Test theCondition


DIFFERENCE BETWEEN DOWHILE AND DOUNTIL• DOWHILE: DO the body of the loop WHILE the condition is TRUE.

• If the condition is TRUE, the body of the loop is executed.

• DOUNTIL: DO the body of the loop UNTIL the condition is TRUE.• If the condition is FALSE, the body of the loop is executed.

DOWHILE DOUNTIL

TRUE

TRUEFALSE

FALSE

Major Difference


STARTPROGRAM


EXITPROGRAM

Test theCondition


REPETITION (Pretest vs. Posttest)Figs_1-140/1-150

STARTPROGRAM


EXITPROGRAM

Test theCondition


DIFFERENCE BETWEEN DOWHILE PRETEST AND POSTEST• PRETEST: The BODY of the loop is executed AFTER the condition is checked.

• POSTTEST: The BODY of the loop is executed BEFORE the condition is checked.• IMPORTANT: The Posttest GUARANTEES that the body of the loop will be executed at least ONCE.

DOWHILE (with Pretest) DOWHILE (with Posttest)

FALSE

Pretest (Before)

FALSE

TRUE

TRUE

Posttest (After)

Major Difference


STARTPROGRAM

Drive Car

Use Gas

EXITPROGRAM

Gas > Empty

Set GasGuage


DOWHILE CONDITION IS TRUE WITH PRETEST• PRETEST: The BODY of the loop is executed AFTER the condition is checked.

DOWHILE (with Pretest) FALSE

TRUE

I check my gas gauge (Condition) before I start driving (Body of Loop).

DOWHILE (with Pretest)

Condition (Pretest)

Body of loop.


STARTPROGRAM

Drive Car

Use Gas

EXITPROGRAM

Gas > Empty

Set Gas Gauge


DOWHILE CONDITION IS TRUE WITH POSTTEST• POSTTEST: The BODY of the loop is executed AFTER the condition is checked.

DOWHILE (with Posttest)

FALSE

TRUE

I check my gas gauge (Condition) after I start driving (Body of Loop).

DOWHILE (with Posttest)

Condition (Posttest)

Body of loop.

COPYRIGHT 2010: Dr. David Scanlan, CSUS FOUR REPETITION LOOPS

STARTPROGRAM

Statements inLoop

EXITPROGRAM

Test LoopCondition

InitializeCondition

STARTPROGRAM

EXITPROGRAM

Test LoopCondition

InitializeCondition

Statements inLoop

DOWHILE condition is TRUE

STARTPROGRAM

Statements inLoop

EXITPROGRAM

Test LoopCondition

InitializeCondition

STARTPROGRAM

EXITPROGRAM

Test LoopCondition

InitializeCondition

Statements inLoop

DOUNTIL condition is TRUE

TRUE

TRUETRUE

TRUE

COPYRIGHT 2010: Dr. David Scanlan, CSUS SOLVE ANY PROBLEM WITH THESE TWO LOOPS

STARTPROGRAM

EXITPROGRAM

Test LoopCondition

InitializeCondition

Statements inLoop

DOWHILE condition is TRUE

STARTPROGRAM

Statements inLoop

EXITPROGRAM

Test LoopCondition

InitializeCondition

DOUNTIL condition is TRUE

TRUE

TRUE

These are the two most common loop variations.Learn them well.

Pretest

Posttest

COPYRIGHT 2010: Dr. David Scanlan, CSUS APPENDEX (FLOWCHART SYMBOLS USED IN THIS COURSE)

Terminal symbol - This symbol indicates the starting or stopping point in the logic. Every flowchart should begin and end with a terminal symbol.

Input/Output symbol - This symbol represents an input or output process in an algorithm, such as reading input or writing output.

Process symbol - Represents any single process in an algorithm, such as assigning a value or performing a calculation. The flow of control is sequential.

Predefined process symbol - Represents a module in an algorithm; that is, a predefined process that has its own flowchart, and code.

Decision symbol - Represent a decision in the logic involving the comparison of two values. Alternative paths are followed depending on whether the decision symbol is true or false.

Terminal

Input/Output

Process

Predefined Process

Decision

Preparation Preparation symbol - In this course, use it for initializing loops.


Flowlines - Connects various symbols in a flowchart, and contain an arrowhead. Use arrowhead when needed for clarity.

APPENDEX (FLOWCHART SYMBOLS USED IN THIS COURSE)


OBJECTIVES:• To understand “For Loops”• To understand “Do Loops”• To apply DoWhile and DoUntil Control Structure logic to “For Loops”and “Do Loops”.

Repitition – Loops

COPYRIGHT 2010: Dr. David Scanlan, CSUS For Loops

For Loop – GENERAL FORMAT

For LoopCounter = InitialValue To TerminalValue‘Program statement(s)

Next LoopCounter

CODE EXAMPLE:

Dim I As IntegerFor I = 1 To 5

lblDisplay.Text = CStr(I) Next I

RESULT:12345

Start

I = 1

I <= 5

Stop

Display I

I = I + 1

True

False

You can use variables here.

This control structure logic is Do While the condition is True with a Pretest

COPYRIGHT 2010: Dr. David Scanlan, CSUS For Loops (Nested Loops)

For Loop – GENERAL FORMAT

For LoopCounter = InitialValue To TerminalValue‘Program statement(s)

Next LoopCounter

CODE EXAMPLE (Nested Loops):

Dim I As IntegerDim J As IntegerFor J = 1 to 2

For I = 1 To 5lblDisplay.Text = CStr(I)

Next IlblDisplay.Text = CStr(J)

Next J

RESULT:1 2 3 4 5 1 1 2 3 4 5 2


These control structures’ logic is Do While the condition is True with a Pretest

Start

I = 1

I <= 5

Stop

Display I

I = I + 1

True

False

J = 1

J <= 2

Display J

J = J + 1

False

True


For Loop with Step – GENERAL FORMAT

For LoopCounter = InitialValue To TerminalValue Step StepValue‘Program statement(s)

Next LoopCounter

CODE EXAMPLE:

Dim I As IntegerFor I = 1 To 5 Step 3

lblDisplay.Text = CStr(I) Next I

RESULT:14

Start

I = 1

I <= 5

Stop

Display I

I = I + 3

True

False



Note: If “Step” is not used, the default Step is + 1.


CODE EXAMPLE:

Dim I As IntegerFor I = 5 To 1 Step - 1lblDisplay.Text = CStr(I) Next I

RESULT:54321

Start

I = 5

I >= 1

Stop

Display I

I = I - 1

True

False

For Loop with Step – GENERAL FORMAT

For LoopCounter = InitialValue To TerminalValue Step StepValue‘Program statement(s)

Next LoopCounter



COPYRIGHT 2010: Dr. David Scanlan, CSUS Do Loops

CODE EXAMPLE:

Dim I As IntegerI = 1Do While I <= 5lblDisplay.Text = CStr(I)

I = I + 1Loop

RESULT:12345

Do Loop – GENERAL FORMAT

Do While (Condition)‘Program statement(s)

Loop

You can use a variable here.

Start

I = 1

I <= 5

Stop

Display I

I = I + 1

True

False


COPYRIGHT 2010: Dr. David Scanlan, CSUS Do Loops

CODE EXAMPLE:

Dim I As IntegerI = 0Do

lblDisplay.Text = CStr(I) I = I + 1

Loop Until (I = 5)

RESULT:12345

This control structure logic is Do Until the condition is True with a Posttest.

Do Loop – GENERAL FORMAT

Do‘Program statement(s)

Loop Until (Condition)

You can use a variable here.

Start

I = 1

I = 5

Stop

Display I

I = I + 1

True

False

Note: A Do Until control structure with a Posttest guarantees that the loop body will always be executed at least once.


You must know the previous loop slides extremely well.

These loops are fundamental to problem solving in programming.

With these fundamental loop structures, you can solve any algorithm requiring repetition.

COPYRIGHT 2010: Dr. David Scanlan, CSUS REPETITION IN EVERYDAY LIFE

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REPETITION (IN EVERYDAY LIFE)