Unit 4 Recap: From Text Representation to Python Programming

Instructions

Read the following recap to reinforce your understanding of how computers represent and process text, how programs are executed, and the variety of programming languages available. This summary covers character encoding systems, program execution steps, common programming languages, and Python basics. Use this recap to review essential concepts from the unit and prepare yourself for future programming endeavors.

Character Encoding: ASCII and Unicode

Computers can only understand binary (0s and 1s), so text characters must be converted to binary values for processing. Two main encoding systems handle this conversion:

ASCII (American Standard Code for Information Interchange)

Developed in the 1960s as one of the first character encoding standards
Uses 7 bits to represent 128 different characters
Includes English letters (uppercase and lowercase), numbers, punctuation marks, and basic control characters
For example, the uppercase letter 'A' is represented as the decimal value 65, which in binary is 01000001
Limited to primarily English characters and cannot represent most international characters

Unicode

Developed in the early 1990s to address ASCII's limitations
Compatible with ASCII (the first 128 Unicode characters are identical to ASCII)
Can represent characters from virtually all of the world's writing systems
Current version contains nearly 150,000 characters
Includes symbols, emojis, and mathematical notations
Uses different encoding forms (UTF-8, UTF-16, UTF-32) to convert characters to binary

Unicode has become the standard for character encoding because it allows computers to handle text in any language, making software truly global. When you type characters on your keyboard, the computer uses these encoding systems to convert each character into its binary representation for processing.

How Programs Are Processed

Programs go through several steps before they run:

Source Code

Human-readable instructions written in a programming language
Saved as text files (e.g., .py for Python, .java for Java)

Compilation/Interpretation

Source code must be translated into machine code
Compilation: Translates the entire program before execution
Interpretation: Translates code line by line while the program runs

Execution

The CPU reads and executes the machine code
The program performs the tasks written in the original code

Different languages follow different paths: C++ and Java are compiled; Python and JavaScript are interpreted; some use a hybrid model.

Common Programming Languages

Programming languages have different purposes, syntax, and features:

Python

High-level, interpreted
Simple, readable syntax
Used for web development, AI, data science, and more
Beginner-friendly

Java

Compiled, object-oriented
Platform-independent (“write once, run anywhere”)
Used for Android apps and enterprise systems
More structured but less beginner-friendly

JavaScript

Interpreted, browser-based
Powers interactive websites
Essential for front-end development
Not related to Java

C/C++

Lower-level with direct hardware access
Used for OSs, game engines, and high-performance apps
Complex syntax and manual memory management
High performance

Other Notable Languages

HTML/CSS: Web structure and styling
SQL: Database queries
Swift: iOS/macOS development
Ruby: Clean syntax, used with Rails for web apps

Each language has strengths suited to specific goals and project needs.

Introduction to Python:

Python is widely used for its simplicity and versatility.

Key Features

Readable syntax that uses indentation to define code blocks
Dynamically typed (no need to declare variable types)
Extensive standard library with pre-built functions
Large community with abundant resources and third-party packages

Python Environment

Python code can be written and run in various environments:
IDEs like PyCharm or VS Code
Simple text editors with separate execution
Online platforms like Replit or Google Colab
Interactive mode through the Python interpreter

Basic Python Syntax

#ThisisacommentinPython

print("Hello,World!")#Thisdisplaystextonthescreen

#Variablesstoredata

name="Alex"

age=15

print(f"Mynameis{name}andIam{age}yearsold.")

#Simplecalculation

result=10+5

print("Theresultis:",result)

Python’s simplicity makes it ideal for beginners, yet powerful enough for advanced use.

Key Takeaways

ASCII uses 7 bits to represent 128 characters while Unicode can represent nearly 150,000 characters from all languages
Computers convert text characters to binary values using encoding systems like ASCII and Unicode
Programs go through translation (compilation or interpretation) before the CPU can execute the instructions
Different programming languages have different strengths, syntax styles, and ideal use cases
Python is popular for beginners due to its readable syntax while remaining powerful enough for professional applications

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