1. Chapter 1: Programming Basics, Python History and Program Components
CS10061 – Introduction to Computer Programming
Chapter 1: Getting Started

2. Why Write Computer Programs?
To assist with a complex situation that requires a human touch
Managing livestock
Patient simulators
Forensics
Weather predictions
Chapter 1: Getting Started

3. Why Write Computer Programs?
To aid with creative thought and higher-level organization
Virtual dancers
Online academic classes
Games
Chapter 1: Getting Started

4. Why Write Computer Programs?
To perform routine or repetitive tasks that follow a clear series of steps or work with electronic information
Package deliveries
Robotics or smart devices
Banking transactions
Chapter 1: Getting Started

5. Programming Basics
A computer program contains instructions written by humans and understandable by computers (statements vs. instructions).
A programming language is used to write a computer program.
Chapter 1: Getting Started

6. Program Basics – Cont’d:
Are all programming languages the same?
No, there are many differences
Machine-like vs. English-like
Compiler (source code) vs. interpreted (dynamic)
Commercial vs. open-source
Platform dependent vs. platform independent
Chapter 1: Getting Started

7. Program Basics – Cont’d:
How do you get started with programs?
Identify the task to solve or automate
Determine the programming language to use
Install the programming language
Read the documentation and learn the jargon
Navigate the working environment (IDLE)
Chapter 1: Getting Started

8. Python’s History Developed by Guido van Rossum Released in 1991
Named after the English comedy troupe Monty Python (many unique references), but the current mascot is a little green snake
Chapter 1: Getting Started

9. Why Use Python? Easy to learn and easy to use
Powerful and efficient (no compilation)
Open-source and free
Platform independent
Integrates or embeds easily with other programming languages
Object-oriented ability is optional
Chapter 1: Getting Started

10. Python IDLEs Python’s IDLEs are working environments for programmers.
Statements are entered:
At a command prompt (>>>)
In a text editor
There are two main IDLEs in Python
Interactive (Shell) Mode (command prompt)
Script Mode (text editor)
Chapter 1: Getting Started

11. Python Interactive (Shell) Mode
Utilizes the command prompt (>>>)
Results are displayed to the screen immediately
Not usable with programs that are already created and saved
Automatically invoked for screen output when a saved program is run
Useful for trying out correct syntax
Chapter 1: Getting Started

12. Python Script Mode Environment is like a text editor (Notepad)
Enables the writing, saving and editing of programs
Invoke by File  New Window from the interactive (shell) mode
Save by File  Save As
Name the file and add the “.py” extension
Run with Edit  Run Script
Results are displayed in a shell window
Chapter 1: Getting Started

13. Program Components Statements do something Commands force action
In English, they convey complete thoughts
In Python, they give complete instructions
Commands force action
Denoted in orange
Case sensitive, specifically lowercase
Part of a statement
Example: print “Hello, World”
Command
Chapter 1: Getting Started

14. Program Components Expressions are something with a value
Denoted in green
Part of a statement
Values may be:
Strings or series of characters
Example: print “Hello, World”
Numbers, a particular number
Example: print 17
Evaluations, say 3 + 1
Example: print 3 + 1
String
Number
Evaluation
Chapter 1: Getting Started

15. Program Components: Syntax Errors
Syntax errors result when the interpreter cannot understand a statement
Misspellings of commands
Incorrect command usage
Other typographical mistakes
The error displayed generally indicates what is wrong with the statement
Familiarize yourself with what syntax errors mean so errors may be fixed quickly
Chapter 1: Getting Started

16. Program Components: Syntax Errors – Cont’d.
Misspellings of commands
Example: prnt “Hello, World” produces
The cursor highlights the last character of the statement
SyntaxError: invalid syntax
Chapter 1: Getting Started

17. Program Components: Syntax Errors – Cont’d.
Incorrect command usage
Example: Hello produces
A new command prompt is displayed
Traceback (most recent call last):
File "<pyshell#0>", line 1, in ?
hello
NameError: name 'hello' is not defined
Chapter 1: Getting Started

18. Program Components: Syntax Errors – Cont’d.
Other typographical mistakes
Example: prnt “Hello, World produces
The word “World” is highlighted to indicate the “token”
SyntaxError: invalid token
Chapter 1: Getting Started

19. Program Components Comments are used for program documentation
Denoted in red
Assists with understanding the code (original developer or subsequent programmers)
Preceded by “#” which is ignored by the interpreter at program execution
Good programming practice dictates the use, especially as the program “header”
Chapter 1: Getting Started

20. Program Components Blank lines Prompts
Used to separate blocks of related statements
Aids in reading the source code
Ignored by the interpreter at program execution
Prompts
Used to ask the user for input
Forces the console window to remain open
Example: raw_input(“\n\nPress the enter key to exit.”)
Chapter 1: Getting Started