1. Input and Output Upsorn Praphamontripong CS 1110
Introduction to Programming
Spring 2017

2. Program Development Cycle
review
Program Development Cycle
Design the
program
Write the
code
Correct
syntax errors
Test the
program
Correct
logic errors
Understand the task the program will perform
Break down the task into a series of steps
Algorithm
Translate an algorithm into code
Two Representation
Pseudocode
Flowchart
CS 1110

3. Algorithm  Pseudocode
review
Algorithm  Pseudocode
Exercise:
Get 2 numbers from the user and display the larger number
Algorithm:
Get the first number
Get the second number
Compare the 2 numbers
Display the larger number
Pseudocode:
Input the first number
Input the second number
If the first number > the second number, display the first number
Otherwise, display the second number
(what if the first number is equal to the second number?)
CS 1110

4. Algorithm  Flowchart Exercise:
review
Algorithm  Flowchart
Exercise:
Get 2 numbers from the user and display the larger number
Start
Input the
first number
Algorithm:
Get the first number
Get the second number
Compare the 2 numbers
Return the larger number
Input the
second number
the first number
is greater than
the second number
Yes No
Display the
first number
Display the
second number
End
CS 1110

5. Input – Process – Output
Exercise:
Get 2 numbers from the user and display the larger number
Input
Process
Output
Check if the first number is greater than the second number
The first
number
The larger number
The second
number
input() function
print() function
CS 1110

6. Reading Input from the Keyboard
input(prompt)
input(“What is your name? ”)
Display the string “What is your name? ” on the screen
Wait for the user to enter something and press Enter
The user’s input is returned as a string
name = input(“What is your name? ”)
The user’s input is returned as a string and assigned to the variable name
CS 1110

7. Variables
A name that represents a value stored in the computer’s memory
Creating variables with assignment statements
statement = "Python is awesome!!!!"
Python is dynamic typed language
statement = "Python is awesome!!!!”
statement = 4
Assignment operator
statement
Python is awesome
String literal
Type: string
Numeric literal
Type: int
Variable reassignment
CS 1110

8. Variable Naming Rules No Python’s key words No spaces
First character must be one of the letters (a…z or A…Z) or an underscore character ( _ )
Case sensitive
Descriptive
Consider t (or x) vs temp vs temperature
How about payrate vs pay_rate vs payRate
CS 1110

9. Displaying Output on the Screen
print(zero or more parameters)
print(“Hello World”)
Display the string “Hello World” on the screen
print(“Hello ” + ”World”)
print(“Hello”, ”World”)
print()
Display an empty line
How about
print(print())?
CS 1110

10. Strings and String Literals
String = a sequence of characters
E.g., “Hello World”
String literal = a value/string that appears in a program, the actual value of the thing it represents
E.g., print(“Hello World”)
Must be surrounded by quotation marks
Quotation marks used
print("Python is awesome!")
print('Python is awesome!')
print('"Python is awesome!"')
print('Python\'s awesome!')
CS 1110