Information Technology, Engineering Faculty

UNIM

Sequence and Selection Structure

Academic Year: 2014-2015

UNIM

(1th Week)

Control Structures (Part 1)

Programming Control Structure

You can write any program by using a combination of three

control structures:

(1) sequence

(2) selection

(3) repetition (a.k.a. iteration or looping)

These three structures are the building blocks of all program

s; they form the foundation of structured programming.

Sequnces Structure (1)

Definition

The sequence control structure is the simplest of the three str

uctures.

It is a program segment where statements are executed in

sequence, one after the other.

Sequnces Structure (2)

Definition

simply series of statements, one after the other, such as th

e following set of statements to calculate net pay:

GrossPay = HoursWorked * HourlyRate

Ded401K = GrossPay * 0.055

Medicare = GrossPay * 0.0145

SocSec = GrossPay * 0.0765

TotDeductions = Ded401K + Medicare + SocSec

NetPay = GrossPay - TotDeductions

Selection Structure (1)

Definition

The selection control structure allows one set of statemen

ts to be executed if a condition is true and another set of

actions to be executed if a condition is false.

A selection structure, also called an "If-Then-Else" structur

e, is flowcharted as follows:

Selection Structure (2)

Block Diagram (1)

If Then

Else

End If

Selection Structure (3)

Block Diagram (2)

If dblTotalSales > 100000 Then

dblBonusAmount = 500

End If

Selection Structure (4)

Type of Selection Structure

1. If Statement

2. Select Case

If Statements (1)

Format

If Then

ElseIf Then

. . .

ElseIf Then

Else

End If

If Statements (2)

Example

If strShiftCode = "1" Then

sngShiftRate = sngHourlyRate

ElseIf strShiftCode = "2" Then

sngShiftRate = sngHourlyRate * 1.1

ElseIf strShiftCode = "3" Then

sngShiftRate = sngHourlyRate * 1.15

Else

MsgBox("Shift code error")

End If

Select Case (1)

Format

Select Case

Case

Case

Case Else

End Select

Select Case (2)

Example

Select Case strShiftCode

Case "1"

sngShiftRate = sngHourlyRate

Case "2"

sngShiftRate = sngHourlyRate * 1.1

Case "3"

sngShiftRate = sngHourlyRate * 1.5

Case Else

MsgBox("Shift Code Error")

End Select

Finish!