1. Program Control using Java - Theory
Department of Computer and Information Science, School of Science, IUPUI
Program Control using Java - Theory
Dale Roberts, Lecturer
Computer Science, IUPUI

2. Algorithms Algorithms is the are part of the problem solving process
‘A’ in STAIR.
All computing problems can be solved by executing a series of actions in a specific order, called an algorithm
Algorithm: procedure in terms of
Actions to be executed
The order in which these actions are to be executed
Program control
Specify order in which statements are to executed

3. Definition of Algorithm
Definition of an Algorithm
consists of unambiguous & computable operations
produce a result
halt in a finite amount of time.
Some scientists add a restriction that the algorithm must halt in a reasonable amount of time. Why would there be resistance to this idea?

4. Control Structures Sequential execution Transfer of control
Statements executed one after the other in the order written
Transfer of control
When the next statement executed is not the next one in sequence
Overuse of goto statements led to many problems
Bohm and Jacopini
All programs written in terms of 3 control structures
Sequence structures: Built into C. Programs executed sequentially by default
Selection structures: Java has three types: if, if/else, and switch
Repetition structures: Java has three types: while, do/while and for

5. Pseudocode Pseudocode An informal language similar to English
Helps programmers develop algorithms
Does not run on computers
Should contain input, output and calculation actions
Should not contain variable declarations
For each student i in the Class
Calculate the student’s average score
If the average score >= 90A% Then
Assign Student[i] grade to ‘A’
End if
End For

6. Control Structures Sequential execution Transfer of control
Statements are normally executed one after the other in the order in which they are written
Transfer of control
Specifying the next statement to execute that is not necessarily the next one in order
Can be performed by the goto statement
Structured programming eliminated goto statements

7. 4.4 Control Structures (Cont.)
Bohm and Jacopini’s research
Demonstrated that goto statements were unnecessary
Demonstrated that all programs could be written with three control structures
The sequence structure,
The selection structure and
The repetition structure

8. 4.4 Control Structures (Cont.)
UML activity diagram (
Models the workflow (or activity) of a part of a software system
Action-state symbols (rectangles with their sides replaced with outward-curving arcs)
represent action expressions specifying actions to perform
Diamonds
Decision symbols (explained in Section 4.5)
Merge symbols (explained in Section 4.7)

9. Control Structures Flowchart
Graphical representation of an algorithm
Drawn using certain special-purpose symbols connected by arrows called flowlines
Rectangle symbol (action symbol):
Indicates any type of action
Oval symbol:
Indicates the beginning or end of a program or a section of code
Single-entry/single-exit control structures
Connect exit point of one control structure to entry point of the next (control-structure stacking)
Makes programs easy to build

10. 4.4 Control Structures (Cont.)
Small circles
Solid circle represents the activity’s initial state
Solid circle surrounded by a hollow circle represents the activity’s final state
Transition arrows
Indicate the order in which actions are performed
Notes (rectangles with the upper-right corners folded over)
Explain the purposes of symbols (like comments in Java)
Are connected to the symbols they describe by dotted lines

11. Fig. 4.1 | Sequence structure activity diagram.

12. Acknowledgements
Deitel, Java How to Program