CMP 131 Introduction to Computer Programming

1
CMP 131Introduction to Computer Programming

• Violetta Cavalli-Sforza
• Week 2, Lecture 2

2
Case Study 1Converting Units of Measurements

• Problem Statement
• You work in a store that sells imported fabric,
  measured in square meters The store customer
  wants to know the equivalent amount in square
  yards. You need to write a program that performs
  the conversion.

3
Case Study 1Converting Units of Measurements

• Analysis
• Input
• Fabric size in square meters (SqMeters).
• Output
• Equivalent amount in square yards (SqYards).
• Relevant Formulas
• The relationship between sq. meter sq. yards
• (1 m2 1.196 y2)

4
Case Study 1Converting Units of Measurements

• Design
• Algorithm
• 1. Read the fabric size in m2.
• 2. Convert size to yd2 using the formula
• (1 m2 1.196 y2).
• 3. Display fabric size in yd2.
• Refinement of step2
• 2.1 Fabric size in yd2 1.196 fabric size in
  m2

5
Case Study 1 Converting Units of Measurements

• Implementation
• Program header
• Give a logical name for your program
• Program Name ConvertSqMtoSqYd
• The name of the source code file of the program
  can be different from the logical name
• File name CONVMYSQ.PAS
• TurboPascal limits file names to 8 characters
• Declaration section
• Memory cells used in your program
• Constant declaration use constants for unchanged
  values
• Variable declaration use variables for values
  that change
• Program body
• Data processing takes place here

6
Case Study 1Converting Units of Measurements

• Implementation (Using Turbo Pascal)
• program ConvertSqMtoSqYd
• Convert square meters to square yards
• const MetersToYards 1.96 conversion constant
• var SqMeters, input - fabric size in meters
• SqYards real output - fabric size in yards
• begin
• Read the fabric size in square meters.
• WriteLn ('Enter the fabric size in square meters
  gt')
• ReadLn(SqMeters)
• Convert the fabric size to square yards.
• SqYards MetersToYards SqMeters
• Display the fabric size in square yards.
• WriteLn ('The fabric size in square yards is ',
  SqYards)
• end.

7
Case Study 1Converting Units of Measurements

• Testing (Output Window)
• A program run
• Enter the fabric size in square meters gt 2.00
• The fabric size in square yards is 2.392000E00

8
Case Study 2 Square Cube

• Problem Statement
• Write a program that calculates the square root,
  square, and cube of a number
• Is this statement clear sufficient for analysis
  design steps?
• NO

9
Case Study 2 Square Cube

• Modified Problem Statement
• Write a program that gets an integer number
  from the user, calculates the square root, square
  and cube of the number and then prints the
  number,the square root, the square, and the cube.
  If the number is negative, the square root should
  not be evaluated. An error message should be
  written instead. The output should be labeled
  with suitable headings.

10
Case Study 2 Square Cube

• Analysis
• Input
• Get a number from the user
• Processing formulas
• Calculate the square root, the square, the cube
• SquareRoot sqrt(Number)
• Square Number x Number.
• Cube Number x Square.
• Output
• Write labels for Number, Square root, Square, and
  Cube
• Write values of Number, Square root, Square, and
  Cube
• (This is one way of doing it)

11
Case Study 2 Square Cube

• Design (Algorithm)
• Pseudocode for initialization
• Clear screen
• Write program purpose
• 2. Pseudocode for Input
• Read Number
• 3. Pseudocode for Processing
• SquareRoot Sqrt(Number)
• Square Number Number
• Cube Square Number
• 4. Pseudocode for Output
• Write Number, Sq. Root,Square, Cube
• Write Number, SquareRoot, Square, Cube
• 5. Pseudocode for termination
• Write Goodbye message

12
Case Study 2 Square Cube

• Implementation
• Program headerprogram SquareNCube
• Declaration section
• const
• HEAD Number Sq.Root Square Cube
  Heading
• var
• Number, input- number being processed
• Square, output - square of the number
• Cube integer output- cube of
  the number
• SquareRoot real output- square root
  of the number
• Program body

13
Case Study 2 Square Cube

• Implementation First draft
• Program Body
• Enclosed between begin end.
• Write algorithm as comments
• begin Program body
• 1. Initialize
• 2. Read Number
• 3. Calculations / Evaluate formulas
• 4. Output heading values
• 5. Terminate
• end.

14
Case Study 2 Square Cube

• Implementation Second draft
• Add Pascal statements in corresponding places
• begin Program body
• 1. Initialize
• Clrscr
• WriteLn(This program calculates square rt.,
  )
• WriteLn(square cube of a given number)
• 2. Read Number
• write (Enter a number )
• readln (Number)
• 3. Evaluate formulas
• if (Number gt 0) then SquareRoot sqrt(Number)
• else WriteLn(Square root can't accept negative
  values)
• Square Number Number evaluate square
• Cube Square Number evaluate cube
• 4. Output heading values
• writeln ( HEAD )
• writeln (Number Sq.Root Square
  Cube)
• writeln ( Number, SquareRoot, Square,
  Cube )

15
Case Study 2 Square Cube

• Implementation (Final Pascal Code)
• program SquareNCube
• const Declaration part
• HEAD N umber Sq.Root Square Cube
  Heading
• var
• Number, input- number being processed
• Square, output - square of the number
• Cube integer output- cube of the
  number
• SquareRoot Real output- square root of
  the number
• begin Program body
• Initialize
• Clrscr
• WriteLn(This program calculates square rt.,
  )
• WriteLn(square cube of a given number)
• Read Number
• write (Enter a number)
• readln (Number)
• Evaluate formulas
• if (Number gt 0)

16
Ideas from Students

• A program for keeping track of my grades in a
  course
• Easy
• A program like those in graphic calculators that
  allows entering the data and will automatically
  display mean/average, the frequency, the median,
  the mode
• Easy, well do a simple version of it
• A special dictionary that will enable me to write
  customized terms and the computer will
  automatically recognize the word I meant and
  transform it by itself. Ex dvlp would stand for
  development. That would be very time saving while
  writing reports.
• Not hard, but in this course we dont learn
  everything we need
• A program for planning courses what courses do I
  take next and what courses do I have left.
• A planning and scheduling problem, can be
  arbitrarily hard
• A program for managing my time and schedule
• If you know an algorithm for doing that, let me
  know.

17
A Limitation

• In this course, given the syllabus, we are
  limited to solving problems where you know
  beforehand how many inputs you will have or where
  you do not have to keep track of the values of
  individual inputs (unless you use external files
  to do so).
• Why?
• Because we will look at only a limited set of
  ways of representing data in memory

18
Case Study 3 Keeping Track of Grades in a Course

• A program for keeping track of my grades in a
  course
• Is this specified clearly enough?

19
Case Study 3 Revised Problem Statement

• A program that will let me enter and store the
  score that I receive for each assessment in the
  course, the maximum score that I could have
  obtained in that assessment, and the name of the
  assessment. When I run the program, it will
  retrieve and display the scores it already knows
  and give me the option to enter the new data.
  When I exit the program, all the data (old and
  new) will be stored to a file so that it can be
  retrieved next time the program is run.

20
Case Study 3 Begin Analysis

• A program that will let me enter and store the
  score that I receive for each assessment in the
  course, the maximum score that I could have
  obtained in that assessment, and the name of the
  assessment. When I run the program, it will
  retrieve and display the scores it already knows
  and give me the option to enter the new data.
  When I exit the program, all the data (old and
  new) will be stored to a file so that it can be
  retrieved next time the program is run.

21
Case Study 3 I/O Analysis

• Input
• Existing data from file
• New data from keyboard
• Output
• Existing data plus new data to file

22
Case Study 3 Processing Analysis

• Processing
• Display existing data
• Decide about how to display the data. E.g.
  Table with headers Assessment My
  Score Max Score HW1
  8 10 .
  .
• Prompt for new data
• Data Name of assessment, My score, Max score
• Decide
• prompt for data one by one or all 3 at a time?
• prompt for data for a single assessment or
  multiple assessments?If multiple assessments,
  how do you indicate you are done?
• Store old and new data
• Decide
• Overwrite the old file?
• Make a new version of the file?
• Decide
• Display all the data the program knows about
  before exiting?

23
Case Study 3 Revised Problem Statement

• A program that will let me enter and store the
  score that I receive for each assessment in the
  course, the maximum score that I could have
  obtained in that assessment, and the name of the
  assessment. When I run the program, it will
• Retrieve and display the scores it already knows
  in a table with suitable headers
• Give me the option to enter data for one or more
  additional assessments or to exit
• If I choose to enter data for an assessment it
  will prompt me for all three values on one line
• After I enter the values it will again give me
  the option to enter new data or to exit.
• When I exit the program
• all the data (old and new) will be stored to a
  new file so that it can be retrieved next time
  the program is run.
• all the data it has for me will be shown.

Are you starting to think that you should use a
spreadsheet instead?