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19/08/2026

Learn how ASCII character codes can be used for simple encryption using a Caesar-style shift.

for Access full course
https://tinyurl.com/3euw3ebv
https://www.udemy.com/course/edexcel-international-gcse-9-to-1-computer-science/?referralCode=5D51B68656EB613EFB58

In this lesson, we explore how readable plaintext can be converted into ciphertext by converting characters to ASCII codes, applying a numeric shift, and converting the new codes back into characters.

You will learn:

What plaintext and ciphertext mean
The purpose of encryption and decryption
How an encryption key works
How ord() converts characters into ASCII codes
How chr() converts ASCII codes back into characters
How positive and negative shifts work
Example: D → 68 → +3 → 71 → G
How to encrypt a complete word such as CAT → FDW
Why ASCII ranges 65–90 and 97–122 matter
How Caesar shifts can wrap around the alphabet
How to handle spaces and punctuation
Why Caesar-style encryption is useful for learning but is not secure modern encryption

This lesson is designed for Pearson Edexcel International GCSE (9–1) Computer Science students and beginners learning about character encoding, ASCII, algorithms, and encryption.

Key idea:
Characters → Codes → Shift → Characters

18/08/2026

Learn how to create an **OpenAI Platform account** and get started with the **OpenAI API** for C # and .NET development.

for Access full course

https://www.udemy.com/course/master-llm-apis-with-c-net-build-ai-apps-using-openai/?couponCode=KEEPLEARNING
https://tinyurl.com/4wtmvu2a

In this beginner-friendly tutorial, we'll explore the OpenAI developer platform and understand the essential tools you'll use when building AI-powered applications.

# # # In this video, you'll learn:

✅ What the OpenAI Platform is
✅ How to create an OpenAI account
✅ How to access the developer platform
✅ How OpenAI Projects organize your applications
✅ How to experiment with the OpenAI Playground
✅ Where to find the OpenAI API documentation
✅ What API keys are and why they must be protected
✅ The difference between ChatGPT and the OpenAI API
✅ How API billing differs from a ChatGPT subscription
✅ The learning path for connecting OpenAI with C # and .NET

We'll follow this journey:

**Create Account → Explore Platform → Create Project → Create API Key → Configure Billing → Choose a Model → Make an API Request → Connect C # Application**

This lesson is part of my **OpenAI API with C # & .NET** tutorial series, where we'll learn step by step how to build real AI-powered applications using OpenAI APIs.

# # # Next Video

**Exploring the OpenAI Platform Dashboard**

# # # Who is this course for?

* C # developers
* .NET developers
* Beginner AI developers
* Software engineers learning LLM APIs
* Students interested in AI application development
* Developers who want to integrate OpenAI into their applications

18/08/2026

How much does it cost to use an LLM API?

for Access full course

https://www.udemy.com/course/master-llm-apis-with-c-net-build-ai-apps-using-openai/?couponCode=KEEPLEARNING
https://tinyurl.com/4wtmvu2a

In this beginner-friendly tutorial, you'll learn how LLM API pricing works and how input tokens, output tokens, model selection, conversation history, and response length can affect the cost of your AI application.

We cover:

🔹 What LLM API pricing means
🔹 Why LLM APIs cost money
🔹 Pay-as-you-go pricing
🔹 Tokens and API costs
🔹 Input tokens vs output tokens
🔹 Why input and output tokens may have different prices
🔹 How to calculate API costs
🔹 Different models and different pricing levels
🔹 How conversation history can increase costs
🔹 Large documents and long responses
🔹 AI Study Assistant cost example
🔹 Model routing
🔹 How to reduce unnecessary token usage
🔹 Monitoring API usage and spending
🔹 Budget alerts and cost controls
🔹 Protecting API keys from unauthorized usage
🔹 LLM API cost optimization strategies

This lesson is useful for developers who want to build AI applications using APIs from providers such as OpenAI, Google Gemini, Anthropic Claude, and other LLM platforms.

By the end of this lesson, you'll understand how to estimate API usage and design more cost-efficient AI applications.

Important: API prices vary between providers and models and can change over time. Always check the provider's current pricing documentation before estimating production costs.

17/08/2026

Learn how **Rate Limits work in LLM APIs** and how to handle them correctly when building AI applications.

for Access full course

https://www.udemy.com/course/master-llm-apis-with-c-net-build-ai-apps-using-openai/?couponCode=KEEPLEARNING
https://tinyurl.com/4wtmvu2a

In this beginner-friendly tutorial, we explain why APIs use rate limits, what happens when you exceed them, and how developers can build reliable applications that handle high API traffic.

You will learn:

• What is an API Rate Limit?
• Why LLM APIs use rate limits
• Requests Per Minute — RPM
• Requests Per Day — RPD
• Tokens Per Minute — TPM
• Requests vs Tokens
• HTTP 429 — Too Many Requests
• 401 Unauthorized vs 429 Too Many Requests
• Rate Limits vs API Quotas
• Retry-After HTTP header
• How API retry logic works
• Exponential Backoff
• Adding jitter to retries
• Bad vs better retry strategies
• Managing rate limits in multi-user applications
• Request queuing and caching
• Per-user rate limiting
• Monitoring API usage
• Building scalable LLM applications

This lesson is especially useful for **C # and .NET developers** who want to build applications using LLM APIs such as OpenAI, Google Gemini, Claude, and other AI services.

By the end of this tutorial, you will understand how to recognize rate-limit problems and design your application to handle them safely and efficiently.

🎓 **Course Series:** Master LLM APIs with C # & .NET
💻 **Level:** Beginner to Intermediate
🤖 **Topics:** LLM APIs, C #, .NET, REST APIs, AI Development

17/08/2026

Test your knowledge of ASCII character codes, ord(), chr(), string indexing, and string building with these 10 practice questions.

for Access full course
https://tinyurl.com/3euw3ebv
https://www.udemy.com/course/edexcel-international-gcse-9-to-1-computer-science/?referralCode=5D51B68656EB613EFB58

This quiz is designed for Pearson Edexcel International GCSE Computer Science students and beginners learning Python character-code functions.

In this video, you will practice:

How ord() converts a character into its numerical code
How chr() converts a numerical code back into a character
Converting words such as CAT into ASCII codes
Converting ASCII codes back into text
Understanding string indexing
Why indexing starts at 0
Building strings by appending characters
ASCII ranges for uppercase letters: 65–90
ASCII ranges for lowercase letters: 97–122
Building HELLO from ASCII codes
Example Questions

ord('c') → ?

chr(100) → ?

CAT → 67 65 84

68 65 84 65 → DATA

72 69 76 76 79 → HELLO

Each question includes the correct answer and a simple explanation, making this video useful for revision and exam preparation.

📚 Course: Pearson Edexcel International GCSE Computer Science
💻 Topic: Character Codes, ASCII, ord() and chr()
🎯 Level: Beginner / IGCSE
📝 Format: 10 Practice Questions with Answers

If you're preparing for your IGCSE Computer Science exam, use this quiz to check your understanding before moving to the next topic.

Next Topic: Simple Encryption Using Character Codes

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17/08/2026

Learn **HTTP Methods** step by step and understand how they are used in **REST APIs, LLM APIs, C #, and .NET**.

for Access full course

https://www.udemy.com/course/master-llm-apis-with-c-net-build-ai-apps-using-openai/?couponCode=KEEPLEARNING
https://tinyurl.com/4wtmvu2a

In this beginner-friendly tutorial, we explain the five most common HTTP methods:

✅ GET – Retrieve data
✅ POST – Send or create data
✅ PUT – Replace or fully update a resource
✅ PATCH – Partially update a resource
✅ DELETE – Remove a resource

You will also learn how HTTP methods work together with:

• API endpoints
• HTTP headers
• JSON request bodies
• CRUD operations
• C # HttpClient
• REST APIs
• LLM APIs

We also look at why **POST is especially important when working with Large Language Model APIs**, where applications send prompts, conversation messages, model settings, temperature values, and other options to an AI service.

# # # C # Methods Covered

GetAsync()
PostAsJsonAsync()
PutAsJsonAsync()
DeleteAsync()

# # # Perfect For

This tutorial is suitable for:

• C # and .NET developers
• Beginners learning REST APIs
• Developers learning LLM APIs
• Students learning API development
• Anyone preparing to build AI applications with C # and .NET

This lesson is part of the **LLM API Tutorial for Beginners** series, where we learn how to build AI-powered applications using **C # and .NET**.

16/08/2026

Learn how **HTTP headers** work when communicating with **LLM APIs using C # and .NET**.

for Access full course

https://www.udemy.com/course/master-llm-apis-with-c-net-build-ai-apps-using-openai/?couponCode=KEEPLEARNING
https://tinyurl.com/4wtmvu2a

In this beginner-friendly tutorial, we explain the most important HTTP headers used in REST API and LLM API requests, including **Authorization, Content-Type, and Accept**.

You will learn how headers provide additional information about an HTTP request, how they differ from the JSON request body, and why correct headers are essential when connecting your C # application to an AI API.

# # # 📚 What You’ll Learn

✅ What HTTP headers are
✅ HTTP header key-value pairs
✅ Structure of an HTTP request
✅ Headers vs JSON request body
✅ Authorization header
✅ Bearer authentication and API keys
✅ Content-Type: application/json
✅ Accept: application/json
✅ Content-Type vs Accept
✅ Request headers vs response headers
✅ Adding HTTP headers using C # HttpClient
✅ Common errors such as 401 and 415
✅ How to protect API keys
✅ Complete C # → LLM API request flow

This lesson is part of my **LLM API Tutorial for C # & .NET Developers**, where we learn step by step how to build applications that communicate with modern AI and Large Language Model APIs.

This tutorial is suitable for **beginners, C # developers, .NET developers, students, and anyone learning REST APIs or LLM API development**.

# # # 🔔 Continue Learning

Subscribe for more tutorials covering:

**LLM APIs • C # • .NET • REST APIs • JSON • Authentication • API Keys • OpenAI • Gemini • Claude • AI Application Development**

16/08/2026

Learn how the ord() and chr() functions are used to convert between characters and numerical character codes.

for Access full course
https://tinyurl.com/3euw3ebv
https://www.udemy.com/course/edexcel-international-gcse-9-to-1-computer-science/?referralCode=5D51B68656EB613EFB58

In this lesson, we explore character-code functions step by step, with simple examples designed for Pearson Edexcel International GCSE Computer Science students.

You will learn:

What ord() does
What chr() does
ord('c') → 99
chr(100) → 'd'
Converting words into ASCII codes
Converting ASCII codes back into text
Traversing strings using indexes
Why string indexing starts at 0
Building strings by appending characters
Validating uppercase ASCII codes from 65–90
Validating lowercase ASCII codes from 97–122
Common ord() and chr() mistakes
How character codes can lead into simple encryption
Examples covered

Character → Code

CAT → 67 65 84

Codes → Character

72 69 76 76 79 → HELLO

Round Trip

DATA → 68 65 84 65 → DATA

This lesson is suitable for beginners learning ASCII, character encoding, Python programming, strings, and data representation.

📚 Course: Pearson Edexcel International GCSE Computer Science
💻 Topic: Data Representation – Character Codes
🎯 Level: Beginner / IGCSE
⏱️ Lesson: Module 6 – Character-Code Functions: ord() and chr()

Next Lesson: Module 7 – Simple Encryption using Character Codes

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14/08/2026

What is an API key, and why do we need one when working with LLM APIs?

for Access full course

https://www.udemy.com/course/master-llm-apis-with-c-net-build-ai-apps-using-openai/?couponCode=KEEPLEARNING
https://tinyurl.com/4wtmvu2a

In this beginner-friendly tutorial, you'll learn how API keys work, how applications send them to APIs, and how to protect them when building applications with C # and .NET.

We cover:

🔑 What an API key is
🔐 Why APIs require authentication credentials
🌐 How API keys are sent with HTTP requests
✅ Valid vs invalid API keys
⚠️ 401 Unauthorized errors
☁️ How to obtain an API key from an API provider
💻 How to store API keys securely in C #
🔒 Environment variables and .NET User Secrets
🚫 Why you should never hardcode API keys
🌐 Secure Blazor WebAssembly architecture
🛡️ Protecting API keys from GitHub exposure
🔄 What to do when an API key is compromised
📊 API usage, billing, quotas, and rate limits

This lesson is especially useful if you're learning how to build AI-powered applications using LLM APIs, C #, ASP.NET Core, Blazor, and .NET.

By the end of this tutorial, you'll understand how to safely manage API credentials before connecting your application to providers such as OpenAI, Google Gemini, Anthropic Claude, and other AI services.

Related Topics

API Basics • REST APIs • JSON Requests • JSON Responses • API Authentication • LLM APIs • C # • .NET • ASP.NET Core • Blazor • AI Development

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13/08/2026

Learn how authentication works in LLM APIs and how to securely connect your applications to AI services such as OpenAI, Google Gemini, and Anthropic Claude.

for Access full course

https://www.udemy.com/course/master-llm-apis-with-c-net-build-ai-apps-using-openai/?couponCode=KEEPLEARNING
https://tinyurl.com/4wtmvu2a

In this beginner-friendly tutorial, you'll learn how API keys and authentication credentials are used to protect LLM APIs and why keeping your credentials secure is essential when building real-world AI applications.

📚 In This Video, You’ll Learn
What API authentication is
Why LLM APIs require authentication
What an API key is
How API keys are generated and used
How authentication works in HTTP requests
What Authorization: Bearer means
Successful vs failed authentication
401 Unauthorized, 403 Forbidden, and 429 Too Many Requests
Authentication vs authorization
Why hardcoding API keys is dangerous
Environment variables and .NET User Secrets
How to securely store API credentials
How to send Bearer tokens using C # and HttpClient
Why API keys should never be stored in Blazor WebAssembly
Secure Blazor + ASP.NET Core + LLM API architecture

This lesson is part of my LLM API tutorial series for C # and .NET developers, where we learn how to build AI-powered applications step by step.

Perfect for beginners learning LLM APIs, REST APIs, C #, .NET, Blazor, OpenAI API, Gemini API, and Claude API.

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