Plotting Graphs Using Turbo C: A Step-by-Step Guide

Graph calculators have always been a fascinating tool for students and professionals to visualize mathematical functions and understand their behavior. One of the classic environments for implementing such functionality was Turbo C, a now-archived but historically significant programming environment. In this article, we will discuss how to create a basic graph plotting program in Turbo C, exploring the necessary steps and techniques involved.

Set Up the Graphics Library in Turbo C

To begin with, you need to make sure your Turbo C environment is properly set up with the graphics libraries included. Turbo C provides a rich set of graphics functions to help you plot graphs effortlessly.

Include the Necessary Headers

The first step is to include the necessary header files in your Turbo C program. These headers define the functions and constants you will need to work with the graphics library.

include graphics.h
include conio.h
include math.h

Graphics.h: This header file contains declarations for various graphics functions and constants.

Conio.h: This header file defines constants and functions related to console I/O.

MATH.H: This header file is required for mathematical functions, particularly those that might be needed to perform calculations for the function you want to plot.

Initialize the Graphics Mode

The next step is to initialize the graphics system. This is done using the initgraph function, which sets up the graphics driver and initializes the graphics mode.

int gd  DETECT; int gm; initgraph(gd, gm, "");

By setting gd to the constant DETECT, the system automatically selects the best graphics driver. The second parameter gm is used to receive the graphics mode. The third parameter is an optional path to the BGI files, which should be left empty if not sure.

Draw the Axes

Now that the graphics system is initialized, you can draw the axes to provide a reference for the plotted graph.

int xOrigin  getmaxx / 2; int yOrigin  getmaxy / 2;
line(0, yOrigin, getmaxx, yOrigin); // X-axis coordinates
line(xOrigin, 0, xOrigin, getmaxy); // Y-axis coordinates

xOrigin and yOrigin are set to the center of the screen. The line function is used to draw the axes.

Plot a Function

To plot the function, you will use a loop to iterate through a range of x-values, calculate corresponding y-values, and then use the putpixel function to plot the points on the graph.

for(int x  -getmaxx/2; x  getmaxx/2; x  ) {
    int y  x * x / 100; // Scale down for better visibility
    putpixel(xOrigin   x, yOrigin - y, WHITE); // Plot the point in white color
}

The function y x2 is plotted in this example. The y-values are scaled down to accommodate the visible range of the screen.

Final Steps

The getch function is used to wait for a key press before closing the graphical window, allowing the user to see the final graph.

getch();
closegraph();

The main function calls the drawGraph function to plot the graph, and returns 0 at the end to signify a successful execution.

Compile and Run the Code

Once you have written the code, ensure that your Turbo C environment is correctly configured with the BGI files. To compile the code, you need to use the appropriate commands specific to your Turbo C version.

Further Enhancements

Now that you have the basic graph plotting program working, there are several enhancements you can make to improve its functionality:

Allow User Input for Different Functions: Modify the program to accept different functions from the user. Add Labels to Axes: Label the axes to provide a clear reference to the plotted function. Implement Zoom and Pan Features: Add functionality to allow the user to zoom in and out, and pan around the graph.

Feel free to experiment and extend the program to meet your specific requirements and interests.