1. Algorithms and Program Development
I. A. How to communicate with computers
Plan what to say
Chose the best phrasing
Actually say it (encode it)
Wait for response
Computers follow instructions created by programmers
Deterministic
No options
Very methodical
No free will
Given the same data, exactly the same results will occur every run

2. Communicating with a Computer
Programming languages bridge the gap between human thought processes and computer binary circuitry.
Programming language: A series of specifically defined commands designed by human programmers to give directions to digital computers.
Commands are written as sets of instructions, called programs.
All programming language instructions must be expressed in binary code before the computer can perform them.
Humans write in programming languages, these get translated into binary. A separate program does the translation

3. The Role of Languages in Communication
Three fundamental elements of language that contribute to the success or failure of the communication cycle:
Semantics – meaning of commands
In computer, each command has ONE meaning
Syntax
Grammatical form
Participants
Human to Machine
II. Difference between human talk and machine talk
Def: Programming language: a series of specifically defined commands designed by human programmers to give directions to digital computers.
Each program solves a particular problem or performs a specific task
A. Def: Semantics – meaning: Commands we want the computer to perform, the meaning of these commands. Each line of a computer language command can have ONE meaning only.
What does it mean to perform an add, it means the contents of memory are added to the contents of the accumulator
B. Def: Syntax: Grammatical form or structure of a language. Rules governing the language, in English = spelling and punctuation
Syntax in computers is very strict
EX. in Java must have a semi-colon ; after every instruction
C. Participants
Humans -----> Machines

4. The Role of Languages in Communication
Semantics: Refers to meaning.
Human language:
Refers to the meaning of what is being said.
Words often pick up multiple meanings.
Phrases sometimes have idiomatic meanings:
let sleeping dogs lie
(don’t aggravate the situation by “putting in your two cents”)
Computer language:
Refers to the specific command you wish the computer to perform.
Input, Output, Print
Each command has a very specific meaning.
Computers associate one meaning with one computer command.

5. The Role of Languages in Communication
Syntax: Refers to form, or structure.
Human language:
Refers to rules governing grammatical structure.
Pluralization, tense, agreement of subject and verb, pronunciation, and gender.
Humans tolerate the use of language.
How many ways can you say no? Do they have the same meaning?
Computer language:
Refers to rules governing exact spelling and punctuation, plus:
Formatting, repetition, subdivision of tasks, identification of variables, definition of memory spaces.
Computers do not tolerate syntax errors.

6. The Role of Languages in Communication
Participants:
Human languages are used by people to communicate with each other.
Programming languages are used by people to communicate with machines.
Human language:
In the communication cycle, humans can respond in more than one way.
Body language
Facial expressions
Laughter
human speech
Computer language:
People use programming languages.
Programs must be translated into binary code.
Computers respond by performing the task or not!

7. The Programming Language Evolution
In the beginning… To use a computer, you needed to know how to program it.
Today… People no longer need to know how to program in order to use the computer.
Investigate how programming languages evolved.
First Generation - Machine Language (code)
Second Generation - Assembly Language
Third Generation - People-Oriented Programming Languages
Fourth Generation - Non-Procedural Languages
Fifth Generation - Natural Languages

8. The Programming Language Evolution
First Generation - Machine Language (code)
Machine language programs were made up of instructions written in binary code.
This is the “native” language of the computer.
Each instruction had two parts: Operation code, Operand
Operation code (Opcode): The command part of a computer instruction.
Operand: The address of a specific location in the computer’s memory.
Hardware dependent: Could be performed by only one type of computer with a particular CPU.
EX: Add two numbers together and store them.
Load register 1 from position 9
MachineCode:
Assembly L R
A R
ST R

9. Review from Hardware Fetch / Execute Cycle
Fetch Cycle
Instructions are “fetched” from the address in the program counter
Execute Cycle
The computer “understands” the binary and does what the instruction says to do.
Actual instructions are very simple
Add, multiply, divide
Logical AND / OR
Move information around in memory
Sense Input / Output
Governed by the Computer Clock
Computer Clock
Computers do one instruction per cycle (either fetch or execute)
The number of cycles the computer does in one second is determined by the computer’s clock
Clock measures in megahertz
Mega of cycles per hertz
Mega is millions
Hertz is seconds
Example, a 1000 MHz ticks a billion times per second
One gigahertz is 1000 MHz or a billion times per second

10. The Programming Language Evolution
Second Generation - Assembly Language
Assembly language programs are made up of instructions written in mnemonics.
Mnemonics: Uses convenient alphabetic abbreviations to represent operation codes, and abstract symbols to represent operands.
Each instruction had two parts: Operation code, Operand
Hardware dependent.
Because programs are not written in 1s and 0s, the computer must first translate the program before it can be executed. -assembler
READ num1
READ num2
LOAD num1
ADD num2
STORE sum
PRINT sum
STOP
An assembler program was used to translate:
Programmers wrote “Source” code and the Assembler created “Object” or machine code.
Data \/
Humans --> Programming language --> Compiler/Assembler --> Binary Code --> Computer
\|/
SOURCE TRANSLATOR OBJECT Results

11. The Programming Language Evolution
Third Generation - People-Oriented Programs
Instructions in these languages are called statements.
High-level languages: Use statements that resemble English phrases combined with mathematical terms needed to express the problem or task being programmed.
Transportable: NOT-Hardware dependent.
Because programs are not written in 1s and 0s, the computer must first translate the program before it can be executed.
We use a Compiler to translate to binary code
One line of source code becomes multiple lines of binary Object code
Give Example of Hi level languages
===========================================================
Second generation First Generation
Hi-level language VS Assembler
sum = subtotal + tax; VS L subtotal
A tax
St sum
Data \/
Humans --> Programming language --> Compiler/Assembler --> Binary Code --> Computer
\|/
SOURCE TRANSLATOR OBJECT Results

12. The Programming Language Evolution
Languages continue to evolve
Many are associated with specific application packages.
Programming-like systems aimed at simplifying the programmers task of imparting instructions to a computer.
Query Languages:
Report Writers:
Application Generators:

13. The Programming Language Evolution
Fourth Generation -
Object-Oriented Languages: A language that expresses a computer problem as a series of objects a system contains, the behaviors of those objects, and how the objects interact with each other.
Object: Any entity contained within a system.
Some popular language examples: C++, Java, Smalltalk
Object Oriented Programming – data and instructions together
Object Oriented design tries to mirror the underlying structure of the real world
Objects are the nouns (or entities ) of any situation
EXAMPLE:
. Take for example, a company.
Nouns might be: Company, Department, Employees Products
We take each noun and say what the data and behavior is of that noun
_______________
Class-section
Classes-section #
Professor name
Class room #
Give Lecture
Give Lab
______________
| Students |
Student Grade
Student SS#
Mid Grade
Final Grade
Record Grades
| |
| name |
| address |
| year |
| ss# |
| take classes |
| get grades |
| |
Each of these Objects relate to other objects in the system. So for example:
Student < >Class-sections
one Student may relate to many Class-sections
one Class-section may have many students relating to it.

14. Advantages of OO Close to the way people think – stable system
Abstraction
Once you know what the inputs and outputs are you can use objects without understanding the details of the programming
Libraries of code exist
Excellent for Graphical User Interface Programs
Re-use
ADVANTAGES of OO
1. Close to the way people think – OO mirrors the underlying structure of the real world
Look for the underlying structure within a situation that will always be true, not just for one
system.
Uses the idea of abstraction: Black Box. If I know how to use the Object, I do not needed to know the details of how it does what it does. If you know the Goes intos and the Goes out ofs, you do not need to know the details of how it is done
4. There are libraries of code that the programmer can use. Especially handy for Graphical User Interface = GUI
Each of the “Objects” of the system is coded up and then they can be re-used in many situations.
>>>> Henry Ford and Deusenberg (1920s)
RE-use is a big OO phrase and reason why people go to the OO technique

15. The Programming Language Evolution
Natural Languages
Languages that use ordinary conversation in one’s own language.
Research and experimentation toward this goal is being done.
Effortless, error-free natural language programs are still some distance into the future.

16. Assembled, Compiled, or Interpreted Languages
All programs must be translated before their instructions can be executed.
Computer languages can be grouped according to which translation process is used to convert the instructions into binary code:
Assemblers
Interpreters
Compilers

17. Assembled, Compiled, or Interpreted Languages
Assembled languages:
Assembler: a program used to translate Assembly language programs.
Produces one line of binary code per original program statement.
The entire program is assembled before the program is sent to the computer for execution.

18. Assembled, Compiled, or Interpreted Languages
Interpreter: A program used to translate high-level programs.
Translates one line of the program into binary code at a time:
An instruction is fetched from the original source code.
The Interpreter checks the single instruction for errors. (If an error is found, translation and execution ceases. Otherwise…)
The instruction is translated into binary code.
The binary coded instruction is executed.
The fetch and execute process repeats for the entire program.
. WOW – looks good on the surface, why not do this all the time? Reads a line and performs it
4. NO Free Lunch -- (I wrote an interpreter. To do 10 different instructions it took 2500 instructions)
5. Interpreted performance is Much slower
a. Useful when running once or twice
b. Production jobs, a job run over and over again – should NOT BE INTERPRETED, but compiled into efficient machine code
Translation: assembler – entire program translated before execution
compiler – entire program translated before execution
interpreter – each line is translated and executed one by one

19. Assembled, Compiled, or Interpreted Languages
Compiled languages:
Compiler: a program used to translate high-level programs.
Translates the entire program into binary code before anything is sent to the CPU for execution.
The translation process for a compiled program:
First, the Compiler checks the entire program for syntax errors in the original source code.
Next, it translates all of the instructions into binary code.
Two versions of the same program exist: the original source code version, and the binary code version (object code).
Last, the CPU attempts execution only after the programmer requests that the program be executed.

20. Programming for Everyone
Several ways to control what your computer does or the way it accomplishes a particular task:
Using Macros
Using HTML to create Web Pages
Scripting
Each allows customization of current applications.

21. Programming for Everyone
Using Macros
Macro: Set of operations within the computer application that have been recorded for later execution.
Once recorded, the macro can be used repeatedly on any document within that application.
A. Macros
Def: A set of operations that has been recorded for later use. Once checked out and saved, the macro can be used many times by different applications.
Example: in Java we are printing out our Name in a box in each program. my print routine. We use this in every program

22. Programming for Everyone
Using HTML to create Web Pages
HTML (HyperText Markup Language): A computer language consisting of special codes intended to design the layout (or markup) of a Web page.
Web browsers interpret the HTML code and display the resulting Web pages.
Web browser: A program that displays information from the WWW.
Each line of HTML is called a tag (formatting instruction).
We will learn more about HTML next week and will write our own
tag – almost every line of HTML contains a tag. A tag is a formatting instruction in HTML. The language that specifies the design and layout of the Web pages. Each tag is delineated by an < > both before and after to set it apart. <title> .....</title>

23. Programming for Everyone
Scripting
Scripting: A series of commands, written to accomplish some task.
Very similar to the concept of a program.
Extends the capabilities of the application where it is being used.
Examples of scripting languages:
VBScript, JavaScript
JavaScript: A scripting language that allows the Web page designer to add functional features to a formatted web page created in HTML.
C. Scripting
Means by which programmers add extensions or additional capabilities to an application.
A script is a series of commands written to accomplish some task. It is very similar to the concept of a program, but not as large or comprehensive.
EXAMPLE: JavaScript is a scripting language that allows the web page designer to add functional features to a formatted web page created with Html

24. Building a Program
Whatever type of problem needs to be solved, a careful thought out plan of attack, called an algorithm, is needed before a computer solution can be determined.
1) Developing the algorithm.
2) Writing the program.
3) Documenting the program.
4) Testing and debugging the program.
Use:
Loaf of Bread
Jar of Peanut Butter
Jar of Jam
Have students write an algorithm in teams of 2 people
Chose 5 teams to write algorithm on the board.
Start with poorest algorithm and act out making of a PB&J sandwich.
Student will gain the knowledge of why a detailed algorithm is needed.

25. Building a Program 1) Developing the algorithm.
Algorithm: A detailed description of the exact methods used for solving a particular problem.
To develop the algorithm, the programmer needs to ask:
What data has to be fed into the computer?
What information do I want to get out of the computer?
Logic: Planning the processing of the program. It contains the instructions that cause the input data to be turned into the desired output data.
Understand the Problem: EXAMPLE – write out names of students in class = Questions arise:
Where do we get the names
How many names
Do the names change from year to year
Do we save the names for future use or do we just print them and then delete them
In what order do we want to print the names
Do I want to know the number of names that I read in?
==========================================

26. Building a Program
A step-by-step program plan is created during the planning stage.
The two major notations for planning detailed algorithms:
Flowchart: Series of visual symbols representing the logical flow of a program.
Pseudocode: A verbal shorthand method that closely resembles a programming language, but does not have to follow a rigid syntax structure.
Detailed description of exact methods used for solving the problem
Logical can be in the form of a flow chart or in pseudocode (English like description)
Play computer after the diagram is done
Try some sample numbers

27. Building a Program 1. If money < $10.00 then go home Else Go out
Flow chart:
Pseudocode:
Start
1. If money < $10.00 then go home
Else Go out
2. Count money
3. Go to number 1
Count Money
Do you
have more than
$10.00?
Yes
Go out No
Go home
End

28. Building a Program 2) Writing the Program 3) Documenting the Program
If analysis and planning have been thoroughly done, translating the plan into a programming language should be a quick and easy task.
3) Documenting the Program
During both the algorithm development and program writing stages, explanations called documentation are added to the code.
Write the Program – code according to the block diagram in the assembler language or the hi-level language that suits your computer and your company’s standards
Make certain that comments are added to the program
Make certain that the pseudo code or flow charts requirements, user acceptance tests are all part of the package so that someone else can pick up the program and you can get promoted
People have been held back from promotions because no one could take over their programs

29. Building a Program 4) Testing and Debugging the Program.
The program must be free of syntax errors.
The program must be free of logic errors.
The program must be reliable. (produces correct results)
The program must be robust. (able to detect execution errors)
User Acceptance testing
Alpha testing: Testing within the company.
Beta testing: Testing under a wider set of conditions using “sophisticated” users from outside the company.
Test and Debug program
Syntax Errors – Compiler / assembler catches these. Each language has its own rules. For example at the end of each instruction in JAVA you must have a semi-colon. Without this the compiler tells you it can not produce machine code.
Logic error. Test with different sets of data -- wanted to print out Barb Zimmerman but printed out ZZZZZZ Zimmerman.
Try bad data. What happens if you put in numbers instead of letters. Does the program give you an error message or does it blow up?
How long a name will it accept. – is it long enough
Try boundary conditions. one student. no students, 100 students. Make certain it still works
User Acceptance testing. When you first get the requirements for a job. You need to decide with the people that will use the program what exactly will constitute acceptance on their part. They may say that they will want to see the program run, run it themselves for 1 week – Once the user accepts the job, they need to sign off that you delivered what you promised.

30. Summary
We traced the evolution of computer programs from machine code to high level languages
We spoke about Object Oriented languages and why they are used today
We discussed assemblers, compilers, and interpreters
We talked about the steps needed to create a program
We concluded by describing the various types of testing
We discussed assemblers, compilers, and interpreters and explained why interpreted code was slower than compiled coded
We talked about algorithms and how detailed they must be