Text Mode Graphics: Techniques and Limitations Explained

Norton tools and That Editor ingeniously utilize text mode to create pixel-by-pixel graphics despite memory limitations.

### Pixel-by-Pixel Graphics in Text Mode: The CGA's Unique Approach
Norton tools and That Editor both achieved **pixel-by-pixel graphics** in text mode, despite the CGA's limited **16KB memory**. The CGA's text-mode display used **80 character cells on 25 rows**, storing data differently by using character cells instead of individual pixels. This unique storage method allowed for **256 possible character symbols** and **16 foreground and 8 background colors**, staying within the **16KB memory limit**.

### The Evolution of Graphics Cards and Text Modes
The text mode font was stored in **read-only memory** on the graphics card, with the CGA being the **first display card**. The VGA, released in 1987, was **backwards compatible** with the CGA and offered a **higher resolution text mode** with the font stored in **regular RAM**. This allowed programmers to **replace the font** and use **code pages for different languages**, offering a variety of **symbol sets**.

### Custom Symbols and Pixel Movement in Early Programs
Early programs had a limit of **256 distinct symbols** on screen, but some used custom graphics for a **unique look**. These custom symbols were still subject to a **grid system**, causing elements like scroll bars to **jump instead of moving smoothly**. The mouse cursor, however, moved **pixel by pixel**, and some programs sacrificed character symbols for graphics, allowing for **smooth animation and dynamic symbol changes**.

### The Animation Process of Font Characters
The animation is created by changing a **single character (C0)** 120 times per second, with additional characters (C8, C9, CD) used for different animations. The developer of Norton Sysinfo anticipated the trick of displaying **all 256 symbols**, but implemented countermeasures to prevent it. The use of symbol cells for animation varied, with the regular person needing **three cells** and the wide person **six**, while the mouse cursor used **six cells** instead of the expected **four**.

### Mouse Cursor Behavior and Personal Update
The 8th column in the program is filled with background color, while the mouse cursor's character slots vary based on what's underneath it. A bug occurs when moving the cursor over nul bytes, causing them to **change to byte B2** and altering the character below. The creator has been busy with a **packed university schedule** but plans to make more videos when they have **free time**.

### The Secrets of Text Mode Graphics: How Norton and That Editor Achieve Pixel-by-Pixel Animation
* 💻 Norton tools like DEFRAG/Speedisk and That Editor demonstrate the ability to **create pixel-by-pixel graphics in text mode**, a feat that seems **impossible at first glance**.
* 🖥 Early graphics cards, such as the CGA, had only **16KB of memory**, which is a fraction compared to modern cards, yet they managed to **display graphics through clever data storage techniques**.
* 📊 The CGA's text mode utilized **80 character cells across 25 rows**, allowing for a total of **128,000 pixels**, but only stored character cells and attributes instead of individual pixels, thus **conserving memory**.
* 🔢 The introduction of the **VGA card in 1987** allowed for **higher resolution text mode** with customizable fonts stored in RAM, enabling programmers to **replace standard symbols with unique graphics** for artistic purposes.
* 🎨 Programs like Scream Tracker exploited these capabilities to create distinctive visuals by using **custom symbols** while still adhering to the limitations of **foreground and background colors**.
* 🔄 That Editor employs a technique where it temporarily **changes font symbols** to animate characters like **PERSON**, effectively allowing **movement across the screen** by manipulating character cells.
* 🖱 Norton tools used a similar method for their mouse cursor, optimizing the use of **character slots for smooth vertical and horizontal movement**, while also employing clever tricks to **manage the display of symbols**.
* 📚 The creator of the video acknowledges their busy university schedule but promises to return with more content, appreciating **viewer engagement and support** during their studies.

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How I got Mario in That Editor — And how Norton Got 🐁

How I got Mario in That Editor — And how Norton Got 🐁