Programming Process

1
Programming Process

• The programmers job can be broken down into six
  programming steps
• Understand the problem
• Plan the logic
• Code the program
• Translate the program into machine language
• Test the program
• Put the program into production

2
Understand the Problem

• Programmers must first understand what it is the
  user wants
• To understand the problem, you must analyze it
• Really understanding the problem may be one of
  the most difficult aspects of programming
• The description of what the user needs may be
  vague
• The user may not even really know what he or she
  wants
• Users who think they know what they want
  frequently change their minds after seeing sample
  output

3
Understand the Problem

• Analysis Really Understanding
• Example
• To invite some people, I need the list of people
  who work during five more years.
• Definite problem or ambiguous problem ?

4
Understand the Problem

• Analysis Really Understanding
• Example
• To invite some people, I need the list of people
  who work during five more years.
• Definite problem or ambiguous problem ?
• Ambiguous problem
• Full-time or part-time worker or both of them ?
• Regular employee or contract employee ?
• Which type of list ?
• A good programmer is often part counselor, part
  detective

5
Programming Process

• The programmers job can be broken down into six
  programming steps
• Understand the problem
• Plan the logic
• Code the program
• Translate the program into machine language
• Test the program
• Put the program into production

6
Plan the Logic

• Programmer plans the steps to the program,
  deciding what steps to include and how to order
  them
• Example
• Planning tour
• Planning party
• The two most common tools
• flowcharts pictorial representation
• Pseudocode English-like representation

7
Plan the Logic

• Flowcharts
• A pictorial representation of the logical steps
  it takes to solve a problem.
• Uses Standardized Symbols
• Utilize Formula Notation
• Typically Read from Top to Bottom or from
• Left to Right on a Page

8
Plan the Logic

• Basic flowchart symbols

Process (Rectangle)
Start/Stop (Terminator)
Input/Output (Parallelogram)
Decision (Diamond)
Connector (Circle)
Flowlines (Arrows)
Predefined Process (Rectangle)
9
Sequence, Selection, Repetition
sequence
selection
repetition
entrance
entrance
entrance
exit
10
Plan the Logic

• Pseudocode
• An English-like representation of the logical
  steps it takes to solve a problem
• pseudo a prefix that means false
• Short English-Like Statements
• Not Standardized
• Proper use of indentation
• Example

start get InputNumber compute
calculatedAnswer as InputNumber times 2
print calculatedAnswer stop
11
Programming Process

• The programmers job can be broken down into six
  programming steps
• Understand the problem
• Plan the logic
• Code the program
• Translate the program into machine language
• Test the program
• Put the program into production

12
Code the program

• Writing the program in one of more than 400
  programming languages
• Pascal, Fortran, C, C, Java..
• Concentrate on the syntax of the language
• Exact instruction, symbol, . ?
• Some very experienced programmers
• successfully combining the logic planning and the
  actual instruction writing, or coding of the
  program, in one step
• Writing a post card
• Writing a cinema scenario

13
Code the program

• Which is harder Planning the Logic or Coding the
  Program?
• Example
• Planning the logic Planning mystery novel
• Coding the program Writing English or Spanish
  based on the original scenario.
• Who gets more annual salary ?

14
Programming Process

• The programmers job can be broken down into
  six programming steps
• Understand the problem
• Plan the logic
• Code the program
• Translate the program into machine language
• Test the program
• Put the program into production

15
Translate the Program

• Objective
• Each computer knows only one language, Machine
  Language.
• High-level Languages must be translated into
  Machine Language
• Need to compiler or interpreter
• Compiler catches every syntax error.
• When writing a program, a programmer might need
  to recompile the code several times
• An executable program is created only when the
  code is free of syntax errors

16
Translate the Program

• Creating an executable program

17
Programming Process

• The programmers job can be broken down into six
  programming steps
• Understand the problem
• Plan the logic
• Code the program
• Translate the program into machine language
• Test the program
• Put the program into production

18
Test the Program

• Why does it need to be tested ?
• Syntax Errors by compile
• Logical Errors by test
• Test
• Executing the program with some sample data
• Seeing whether or not the results are logically
  correct.
• being tested with many sets of data carefully
• Example

start get InputNumber compute
calculatedAnswer as InputNumber times 20
print calculatedAnswer stop
19
Programming Process

• The programmers job can be broken down into six
  programming steps
• Understand the problem
• Plan the logic
• Code the program
• Translate the program into machine language
• Test the program
• Put the program into production

20
Put the program into the production

• Once the program is tested adequately, it is
  ready for the organization to use.
• Putting the program into production might mean
  simply running the program once if it was written
  to satisfy a users request for a special list.

21
Flowchart Pseudocode

• Flowcharts (pictorial representations) and
  pseudocode (English-like representations) are
  used by programmers to plan the logical steps for
  solving a programming problem
• Some professional programmers prefer writing
  pseudocode to drawing flowcharts, because using
  pseudocode is more similar to writing final
  statements in programming language

22
Flowchart Pseudocode

• Almost every program involves the steps of input,
  processing, and output, necessitating some
  graphical way to separate them
• Arithmetic operation statements are examples of
  processing in a flowchart, where you use a
  rectangle as the processing symbol containing a
  processing statement

23
Flowchart Pseudocode

• To represent an output statement, you use the
  parallelogram, which is also the same symbol used
  for input statements

24
Flowchart Pseudocode

• In flowcharts
• Arrows, or flowlines, connect and show the
  appropriate sequence of steps
• A terminal symbol, or start/stop symbol, should
  be included at each end
• Often, start or begin is used as the first
  terminal symbol and end or stop is used in
  the other
• The standard terminal symbol is shaped like a
  racetrack often called a lozenge, because it
  resembles the shape of a medicated candy lozenge
  you might use to soothe a sore throat

Flowlines (Arrows)
Start/Stop (Terminator)
25
Flowchart Pseudocode

• Complete flowchart for the program that doubles a
  number, and the pseudocode for the same problem

start get InputNumber compute
calculatedAnswer as InputNumber times 2
print calculatedAnswer stop
26
Naming Variables

• Variables
• memory locations, whose contents can vary or
  differ over time.
• reasonable and descriptive variable names
• Example
• InputNumber
• caluculatedAnswer

start get InputNumber compute
calculatedAnswer as InputNumber times 2 print
calculatedAnswer stop
27
Naming Variables

• Naming Rules
• Every programming language has its own set of
  rules for naming variables.
• most languages allow both letters and digits
  a,b,c, 1,2,3
• some languages allow hyphens and/or underscores
  - _
• some allow dollar signs or other special
  characters , , _at_
• some allow for foreign characters Japanese,
  Spanish
• different languages put different limits on
  lengths
• some languages are case sensitive, others are not
  name, Name
• in general, variable names may not begin with a
  digit name1

28
Naming Variables

• Textbook Conventions two rules
• (1) Variable names must be one word
• can contain letters, digits, hyphens,
  underscores, with the exception of spaces.
• (2) Variable names should have some appropriate
  meaning
• Undesirable G, u84, fred, mike, richard, pink,
• Desirable rate, name, age, count, score,
  index, lastName

employeeLastName, 5employeeLastName,
employeeLast, empLast, emlstnam,
lastNameofTheEmployeeInQuestion, last name (x),
employeelastname,
29
Naming Variables

• Assignment values to variables
• Whatever operation is performed to the right of
  the equal sign results in a value that is placed
  in the memory location to the left of the equal
  sign.

compute calculatedAnswer as InputNumber times
2 is the same as calculatedAnswer InputNumber
2
30
Naming Variables

• Constant
• A memory location, similar to a variable, except
  its value never changes during a program.
• taxRate .0825
• Pi 3.141592
• Variables
• memory locations, whose contents can vary or
  differ over time.

31
Naming Variables

• Data Types two basic types
• Character
• Character a b c d e
• Character string Richard Michale
• Numeric
• Integer , -3, -2, -1, 0, 1, 2, 3, .
• Floating-Point , -2.0, -1.5, -1, -0.5, 0, 0.5,
  1.0, .

32
Ending a Program

• Infinite loop

start get InputNumber compute
calculatedAnswer as InputNumber times 2
print calculatedAnswer get
InputNumber compute calculatedAnswer as
InputNumber times 2 print
calculatedAnswer get InputNumber compute
calculatedAnswer as InputNumber times 2
print calculatedAnswer stop
start
get InputNumber
calculatedAnswerInputNumber2
Print calculatedAnswer
33
Ending a Program

• An infinite loop is a repeating flow of logic
  with no end
• To end the program,
• set a predetermined value for inputNumber that
  means Stop the program!
• The program can then test any incoming value for
  inputNumber and, if it is a 0, stop the program
• Testing a value is also called making a decision
• Represented in flowchart by diamond shape called
  a decision symbol

34
Ending a Program

• Decision symbol

start
start
get InputNumber
get InputNumber
Yes
inputNumber 0 ?
stop
No
calculatedAnswerInputNumber2
calculatedAnswerInputNumber2
Print calculatedAnswer
Print calculatedAnswer
35
Ending a Program

• Dummy value
• A pre-selected value that stops the execution of
  a program is often called a dummy value since it
  does not represent real data, but just a signal
  to stop
• Sometimes, such a value is called a sentinel
  value because it represents an entry or exit
  point, like a sentinel who guards a fortress

36
Using a Connector

• If a flowchart has six processing steps and a
  page provides room for only three, you might
  represent the logic as shown below
• On-page connector symbol
• Off-page connector symbol

37
Evolution of Programming Technique

• Currently, there are two major techniques used to
  develop programs and their procedures
• Procedural programming focuses on the procedures
  that programmers create
• Object-oriented programming, focuses on objects,
  or things, and describes their features, or
  attributes, and their behaviors

38
Summary

• A programmers job involves six steps
• Understanding the problem
• Planning the logic
• Coding the problem
• Translating the program into machine language
• Testing the program
• Putting the program into production
• When programmers plan the logic for a solution to
  a programming problem, they often use flowcharts
  or pseudocode

39
Summary

• Testing a value involves making a decision
• Most programming languages use the equal sign to
  assign values to variables
• Procedural and object-oriented programmers
  approach program problems differently