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Introduction%20to%20Programming

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Rattapoom Waranusast Department of Electrical and Computer Engineering Faculty of Engineering, Naresuan University – PowerPoint PPT presentation

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Title: Introduction%20to%20Programming


1
Introduction to Programming
305171 Computer Programming Rattapoom
Waranusast Department of Electrical and Computer
Engineering Faculty of Engineering, Naresuan
University
2
What is Algorithm
  • Algorithm is a process or a set of rules to be
    followed in calculations or other problem-solving
    operations.
  • The instructions should be simple and clear
    enough so that each step can be done without
    confusion.

3
Example
  • This is an example of an algorithm for sorting
    cards with colors on them into piles of the same
    color
  • Pick up all of the cards.
  • Pick a card from your hand and look at the color
    of the card.
  • If there is already a pile of cards of that
    color, put this card on that pile.
  • If there is no pile of cards of that color, make
    a new pile of just this card color.
  • If there is still a card in your hand, go back to
    the second step.
  • If there is not still a card in your hand, then
    the cards are sorted, you are done.

4
Real-world Algorithm
5
Algorithm?
6
What is A Program?
  • A program is a very specific set of steps and
    rules.
  • A program is an implementation of an algorithm in
    a particular language to run on a computer
    (usually a particular kind of computer)
  • Algorithm what we want to do
  • Program what we actually did
  • The process of creating a program is called
    programming.
  • Programming is breaking a task down into small
    steps and rules.

7
Lets do some Examples
  • Put these words in alphabetical order apple,
    zebra, abacus
  • Count the number of words in these sentences
  • Programming really can be fun.
  • John,do it again.
  • Some people just love to type really short
    lines, instead of using the full width of the
    page.

8
Flowchart
  • A flowchart is a diagram that depicts the flow
    of a program.

9
Basic Flowchart Symbols
  • Terminals
  • represented by rounded rectangles
  • indicate a starting or ending point

Terminal
10
Basic Flowchart Symbols
  • Input/Output Operations
  • represented by parallelograms
  • indicate an input or output operation

Input/Output Operations
11
Basic Flowchart Symbols
  • Processes
  • represented by rectangles
  • indicates a process such as a mathematical
    computation or variable assignment

Process
12
Stepping Through the Flowchart
  • Variable Contents Hours ? Pay Rate ? Gross
    Pay ?

13
Stepping Through the Flowchart
How many hours did you work?
  • Variable Contents Hours ? Pay Rate ? Gross
    Pay ?

14
Stepping Through the Flowchart
How many hours did you work? 40
  • Variable Contents Hours 40 Pay Rate ? Gross
    Pay ?

15
Stepping Through the Flowchart
How many hours did you work? 40
How much do you get paid per hour?
  • Variable Contents Hours 40 Pay Rate ? Gross
    Pay ?

16
Stepping Through the Flowchart
How many hours did you work? 40
How much do you get paid per hour? 300
  • Variable Contents Hours 40 Pay Rate
    300 Gross Pay ?

17
Stepping Through the Flowchart
How many hours did you work? 40
How much do you get paid per hour? 300
  • Variable Contents Hours 40 Pay Rate
    300 Gross Pay 12000

18
Stepping Through the Flowchart
How many hours did you work? 40
How much do you get paid per hour? 300
12000
  • Variable Contents Hours 40 Pay Rate
    300 Gross Pay 12000

19
Stepping Through the Flowchart
How many hours did you work? 40
How much do you get paid per hour? 300
12000
  • Variable Contents Hours 40 Pay Rate
    300 Gross Pay 12000

20
Four Flowchart Structures
  • Sequence
  • Decision
  • Repetition
  • Case

21
Sequence Structure
  • a series of actions are performed in sequence
  • The pay-calculating example was a sequence
    flowchart.

22
Decision Structure
  • One of two possible actions is taken, depending
    on a condition.
  • In the flowchart segment below, the question is
    x lt y? is asked. If the answer is no, then
    process A is performed. If the answer is yes,
    then process B is performed.

Yes
No
23
Repetition Structure
  • A repetition structure represents part of the
    program that repeats. This structure is commonly
    known as a loop.
  • In the flowchart segment, the question is x lt
    y? is asked. If the answer is yes, then Process
    A is performed. The question is x lt y? is asked
    again. Process A is repeated as long as x is less
    than y. When x is no longer less than y, the
    repetition stops and the structure is exited.

24
Case Structure
  • One of several possible actions is taken,
    depending on the contents of a variable.
  • The structure below indicates actions to perform
    depending on the value in years_employed.

25
Connector
  • Sometimes a flowchart will not fit on one page
    length.
  • A connector (represented by a small circle)
    allows you to connect two flowchart segments on
    the same page.
  • The A connector indicates that the second
    flowchart segment begins where the first segment
    ends.

26
Modules
  • The position of the module symbol indicates the
    point the module is executed.
  • A separate flowchart can be constructed for the
    module.

27
Other common Symbols
  • Off-page connector
  • Used to connect remote flowchart portion on
    different page
  • Comment
  • Used to add description
  • Document
  • Used to represent a print out
  • Database
  • Used to represent a database

28
Pseudocode
  • Pseudocode is a compact and informal high-level
    description of a computer programming algorithm
    that uses the structural conventions of a
    programming language, but is intended for human
    reading rather than machine reading. Pseudocode
    typically omits details that are not essential
    for human understanding of the algorithm, such as
    variable declarations, system-specific code and
    subroutines. (Wikipedia)

29
Pseudocode
  • Pseudocode generally does not actually obey the
    syntax rules of any particular language.
  • There is no systematic standard form.
  • Pseudocode may therefore vary widely in style,
    from a near-exact imitation of a real programming
    language at one extreme, to a description
    approaching formatted prose at the other.

30
A Guideline for Pseudocode
  • Write only one statement per line
  • Capitalize initial keyword
  • Indent to show hierarchy
  • End multiline structures
  • Keep statements language independent

31
Example
  • BEGIN Procedure_NetCalc
  • READ name, grossPay, taxes
  • IF taxes gt 0
  • net grossPay taxes
  • ELSE
  • net grossPay
  • ENDIF
  • WRITE name, net
  • END Procedure_NetCalc

32
Decision Structure
  • Pseudocode
  • IF Y gt 3
  • X 5
  • ELSE
  • X 10
  • ENDIF

33
Repetition Structure and Module
  • BEGIN
  • count 0
  • WHILE count lt 10
  • DO Process
  • ENDWHILE
  • WRITE The End
  • END
  • BEGIN Process
  • ADD 1 to count
  • WRITE count
  • END Process

34
Flowchart vs Pseudocode
Advantages Disadvantages
Flowchart Standardized Visual Hard to modify Structured design elements not implemented Special software required
Pseudocode Easily modified Implements structured concepts Done easily on word processor Not visual No accepted standard, varies from company to company
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