Solution for Exercise 11-15

ex1115

#include <stdio.h>
#include <math.h>

#ifndef M_PI
#define M_PI 3.14159
#endif

int main()
{
    const float amplitude=70, wavelength=0.1;
    float graph,s,x;

    for(graph=0;graph<M_PI;graph+=wavelength)
    {
        s = sin(graph);
        for(x=0;x<s*amplitude;x++)
            putchar('*');
        putchar('\n');
    }
    return(0);
}

Output

*******
**************
*********************
****************************
**********************************
****************************************
**********************************************
***************************************************
*******************************************************
***********************************************************
***************************************************************
******************************************************************
********************************************************************
*********************************************************************
**********************************************************************
**********************************************************************
**********************************************************************
*********************************************************************
*******************************************************************
****************************************************************
*************************************************************
*********************************************************
*****************************************************
************************************************
******************************************
*************************************
******************************
************************
*****************
**********
***

Notes

* Don't sweat it if the trigonometry in this code boggles you.

* Here is the graphical representation of a sine wave:

Sine Wave

* The constant M_PI is required because the C language trig functions deal with radians, not degrees. So in Line 14, the for loop goes from zero to M_PI radians, which is half a circle.

* Refer to my information on preprocessor directives if you'd like to know more about #ifndef.

* You can make adjustments to the code by changing a few of the key values. I've defined those values as constants, which makes them easier to change:

* The constant amplitude sets the height of the graph (left-to-right) as measured by screen columns. To make the graph more squat, change the value to something smaller. The wavelength constant is related to the number of rows in the output.

Exercise ex1116 →