Introduction to Programming

1
Introduction to Programming

• What is an algorithm?
• Input and output
• Sequential execution
• Conditional execution
• Reading
• Chapter 1 in either text
• Lewis Loftus, or Savitch

2
Problems and Algorithms

• problem A task to be performed
• algorithm A procedure for solving a problem
• Algorithms are
• precise and unambiguous
• methodical and effective
• abstract

3
Sample Problems

• Is a given integer even or is it odd?
• For each integer in a list, is it even or odd?
• Play tic-tac-toe so you never lose
• Play tic-tac-toe so you always win
• Play chess so you always win

4
Programs and Computers

• program An algorithm written down in some
  language, e.g., English, Russian, Java, MatLab.
• computer A device that can execute programs
  written in programming languages, e.g., Java,
  MatLab, C, C, Fortran, Basic.

5
Algorithms and Programs
the thing with the property threeness
6
Problem 1

• Is a given integer even or odd?
• more precisely
• An integer is written on a card. If the integer
  is even, say even, otherwise say odd.

7
Algorithm / Program A

• 1. Get the integer from the card.
• 2. Divide the integer by 2.
• 3. If the remainder is 0, say even, otherwise
  say odd.
• Test
• 123456789

8
Algorithm / Program B

• 1. Get the integer from the card.
• 2. If the rightmost digit is 0, 2, 4, 6, or 8 say
  even, otherwise say odd.
• Test
• MCMXCIX

9
Input and Output

• input Bring data into the program, e.g., the
  integer from the card.
• output Send values out from the program, e.g.,
  the text even or odd.

10
Sequential and Conditional Execution

• sequential execution Perform sequence of
  computation steps in order, e.g., step 1, step 2,
  step 3.
• conditional execution Perform one of several
  steps based on a test, e.g., either print even
  or print odd based on whether the remainder is
  0 or not.

11
Things to Do Now(if you choose CS100J)

• Web Browse CS100J web pages
• http//courses.cs.cornell.edu/cs100j/2002fa/
• Program 1 get description from web (Homework),
  and start
• Sections pick one and attend. (Start next week)
• Reading Lewis Loftus, Chapter 1
• Lecture (Tuesday) Kimball B11