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## C Programming Exercise - Example 58: Drawing Rectangles with Graphics In this exercise, we will explore how to use the `graphics.h` library in C to draw geometric shapes. Specifically, we will learn how to use the `rectangle()` function to draw nested squares, combine them with other shapes like circles and lines, and render text on the screen. --- ### 1. Introduction to `graphics.h` and `rectangle()` The `graphics.h` library was historically used in DOS-based environments (such as Turbo C/C++) to create 2D graphics. The `rectangle()` function is used to draw a 2D outline of a rectangle on the screen using the current drawing color and line style. #### Syntax: ```c void rectangle(int left, int top, int right, int bottom); ``` #### Parameter Description: * **`left`**: The X-coordinate of the top-left corner. * **`top`**: The Y-coordinate of the top-left corner. * **`right`**: The X-coordinate of the bottom-right corner. * **`bottom`**: The Y-coordinate of the bottom-right corner. --- ### 2. Problem Analysis The goal of this program is to draw a series of concentric, expanding squares (rectangles with equal width and height) using a loop. 1. **Initialization**: Initialize the graphics system using `initgraph()`. 2. **Background Color**: Set the background color to yellow using `setbkcolor(YELLOW)`. 3. **Looping Rectangles**: Start with a small central square defined by coordinates `(x0, y0)` and `(x1, y1)`. In each iteration of a `for` loop: * Draw the rectangle. * Expand the boundaries outward by shifting the top-left corner up and left (`x0 -= 5`, `y0 -= 5`) and the bottom-right corner down and right (`x1 += 5`, `y1 += 5`). 4. **Text and Accents**: Display a text message using `outtextxy()`, draw an underline using `line()`, and draw an outer bounding circle using `circle()`. --- ### 3. Source Code Implementation Below is the complete C program. This code is designed to run in environments that support the legacy Turbo C graphics library (such as Turbo C++, WinBGIm, or DOSBox). ```c /** * Description: C Exercise Example 58 - Drawing Rectangles * Target Environment: Turbo C / DOSBox / WinBGIm */ #include #include int main() { int x0, y0, x1, y1, driver, mode, i; // Set graphics driver to VGA and mode to VGAHI (640x480 resolution) driver = VGA; mode = VGAHI; // Initialize the graphics system initgraph(&driver, &mode, ""); // Set background color to yellow setbkcolor(YELLOW); // Initial coordinates for the innermost square x0 = 263; y0 = 263; x1 = 275; y1 = 275; // Draw 19 nested squares, expanding outwards for(i = 0; i <= 18; i++) { setcolor(1); // Set drawing color (Blue in standard VGA palette) rectangle(x0, y0, x1, y1); // Expand coordinates for the next iteration x0 = x0 - 5; y0 = y0 - 5; x1 = x1 + 5; y1 = y1 + 5; } // Set text style: Default font, Horizontal direction, Size 2 settextstyle(DEFAULT_FONT, HORIZ_DIR, 2); // Output text at coordinates (150, 40) outtextxy(150, 40, "How beautiful it is!"); // Draw a horizontal line under the text line(130, 60, 480, 60); // Set color to Green (2) and draw a bounding circle around the squares setcolor(2); circle(269, 269, 137); // Wait for a key press before closing the graphics window getch(); closegraph(); return 0; } ``` --- ### 4. Key Functions Explained * **`initgraph(&driver, &mode, "path")`**: Initializes the graphics system by loading the graphics driver from disk and putting the system into graphics mode. * **`setbkcolor(color)`**: Sets the background color of the viewport. * **`setcolor(color)`**: Sets the current drawing color. In the standard 16-color VGA palette, `1` represents Blue and `2` represents Green. * **`circle(x, y, radius)`**: Draws a circle with its center at `(x, y)` and the specified `radius`. * **`outtextxy(x, y, text)`**: Displays a string at the specified `(x, y)` coordinate. --- ### 5. Modern Compilation Considerations Since `graphics.h` is a non-standard, deprecated library from the MS-DOS era, compiling this code on modern operating systems (Windows 10/11, macOS, Linux) with modern compilers (GCC/Clang) requires extra setup: 1. **Using Turbo C++ in DOSBox**: This is the easiest way to run the code exactly as written. You can download a pre-configured Turbo C++ environment that runs inside the DOSBox emulator. 2. **Using WinBGIm (Windows)**: WinBGIm is a port of the Turbo C graphics library for modern GCC compilers (like MinGW). You can link `libbgi.a` and include `graphics.h` in IDEs like Code::Blocks or Dev-C++. 3. **Modern Alternatives**: If you are building modern graphical applications in C, it is highly recommended to use modern cross-platform libraries such as **SDL2**, **Raylib**, or **OpenGL** instead of the legacy `graphics.h`.