Lecture1: Introduction to Programming and Problem Solving

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Lecture1 Introduction to Programming and
Problem Solving

• Daniel Chen

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Topics

• 1. Computer Operations
• 2. What is programming?
• 3. What are the steps of program development?
• 4. What is structured programming
• 5. Data and data structures

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Six Basic Computer Operations

• 1. A computer can receive (input) data
• 2. A computer can store data in memory
• 3. A computer can perform arithmetic and
  manipulate text strings
• 4. A computer can compare the contents of two
  memory locations and select one of two
  alternatives
• 5. A computer can repeat a group of operations
• 6. A computer can output information (processed
  data)

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Computer Operations
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What is Programming

• Program a very specific set of instructions (or
  command lines) that making a computer do what you
  want it to do
• Programming the process of creating a program
• the development of a solution to an identified
  program, and setting up of a related series of
  instructions which, when directed through
  computer hardware, will produce the desired
  results

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Steps in program development

• 1. Define the problem
• 2. Outline the solution
• 3. Develop the outline into an algorithm
• 4. Test the algorithm for correctness
• 5. Code the algorithm into a specific
  programming language
• 6. Run the program on the computer
• 7. Document and maintain the program

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Define the Problem

• Divide the problem into three components
• (called IPO)
• Inputs what do you have?
• Outputs what do you want to have?
• Processing
• how do you go from inputs to outputs?
• A defining diagram is recommended

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Outline the Solution

• The major processing steps involved
• The major subtasks (if any)
• The major control structures (e.g. repetition
  loops)
• The major variables and record structures
• The mainline logic

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Develop the Outline into an Algorithm

• Algorithm is a set of precise steps that describe
  exactly the tasks to be performed, and the order
  in which they are to be carried out
• Pseudocode (a form of structured English) is used
  to represent the solution algorithm

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Test the Algorithm for Correctness

• The main purpose of desk checking the algorithm
  is to identify major logic errors early, so that
  they may be easily corrected
• Test data needs to be walked through each step in
  the algorithm, to check that the instructions
  described in the algorithm will actually do what
  they are supposed to

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Code the Algorithm into a Specific Programming
Language

• Only after all design considerations have been
  met should you actually start to code the program
  into your chosen programming language (e.g.
  Visual Basic, Java, C)

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Run the Program on the Computer

• This step uses a program compiler and
  programmer-designed test data to machine test the
  code for syntax errors
• Program complier translate high-level languages
  (e.g. VB) to low-level machine language before
  execution

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Document and Maintain the Program

• Not the last step in the program development
  process
• An ongoing task from the initial definition of
  the problem to the final test result
• Involves both external documentation (such as
  hierarchy charts) and internal documentation that
  may have been coded in the program

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Example 1 Circle

• Calculate the circumference and area
• IPO
• I radius
• P calculate circumference and area as
  
• circumference 2 P I radius
• areaPI radius 2
• O radius, circumference, area

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Circle (Pseudocode)

• Begin program
• get radius, PI
• circumference 2 P I radius
• areaPI radius radius
• display circumference, area
• End program

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Example 2 Payroll Problem

• I time cards, pay rate, deductions
• P calculate gross pay, calculate net pay
• hours worked end time start time
• gross pay hours worked pay rate
• net pay gross pay - deductions
• O payroll records (gross pay, deductions net pay)

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Payroll problem (cont.)

• Subtasks
• Deductions include required (taxes) and optional
  (staff benefits)
• Gross pay may include vacation time, sick time,
  personal time.
• Major control structures
• Repeat payroll processing for all employees
• Major variables
• Employee pretty much static data
• Name, address, department,
• Employee non-static historical data
• Year to date earnings,
• Employee current data
• Hours worked, vacation hours, sick hours,
• Global data
• Tax tables federal state , tax cutoffs

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Payroll Problem Pseudocode

• (assuming deductions are given)
• Begin program
• Read Start_time, End_time, Pay_rate, Deductions
• Hours_worked End_time Start_time
• Gross_pay Hours_worked Pay_rate
• Net_Pay Gross_pay Deductions
• Display Gross_pay, Deductions, Net_pay
• End program

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Structured Programming

• Top-Down
• outline a general solution to the problem first
• start coding at the beginning of the problem and
  work systematically through each step until
  reaching the end
• Modular
• keep things together that belong together
• e.g. calculating sales tax or printing report
  headings
• Three control structures
• Sequence (one after another)
• Selection (making decisions/choices)
• Repetition (doing things over and over)

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Sequence

• The straightforward execution of one processing
  step after another
• pseudocode statements
• statement a
• statement b
• statement c

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Example of Sequence in VB

• Private Sub CmdTotlasales_Click()
• Numbercontracts CInt(TxtTotalContracts.Text)
• Pricecontracts CCur(TxtContractPrice.Text)
• Totalrevenue Numbercontracts Pricecontracts
• TxtTotalSales.Text
• FormatCurrency(Totalrevenue, 2)
• End Sub

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Selection

• Pseudocode statements
• IF condition p is true THEN
• statement(s) in true case
• ELSE
• statement(s) in false case
• ENDIF
• If condition p is true then the statement or
  statements in the true case will be executed, and
  the statements in the false case will be skipped

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Example of Selection in VB

• If strGrade A then
• sngGradePoint 4.0
• Elseif strGrade B then
• sngGradePoint 3.0
• Elseif strGrade C then
• sngGradePoint 2.0
• Elseif strGrade D then
• sngGradePoint 1.0
• Else
• sngGradePoint 0.0
• End If

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Repetition

• A set of instructions to be performed repeatedly,
  as long as a condition is true
• Pseudocode statements
• DOWHILE condition p is true
• statement block
• ENDDO

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Example of Repetition

• Add up all odds between 1 to 20
• 1 3 5 7 9 19 ?
• Humans way
• 1 3 4
• 4 5 9
• 9 7 16
• 
  81 19 100

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Example of Repetition (Cont)

• Computers way
• Private Sub CmdCalcSum_Click()
• intSum 0 intCounter 1 Do while
  intCounter lt 20 intSum intSum
  intCounter intCounter intCounter 2 Loop
• End sub

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Data

• Variable
• the name given to a collection of memory cells,
  designed to store a particular data item
• the value stored in that variable may change or
  vary as the program executes
• Constant
• a data item with a name and a value that remain
  the same during the execution of the program
  (e.g. 8, 10)
• Literal
• a constant whose name is the written
  representation of its value (e.g. 8, 10)

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Data type

• Integers
• whole numbers
• Real
• Numbers with a decimal point
• Two choices in VB single and double
• Character
• Boolean
• True or False

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Data Structures(also called data aggregates)

• Record
• One set of related data
• A time card an invoice
• File
• A set of related records
• Array
• A collection of data that have same data type
• String
• An array of characters
• Hello Daniel Chen