Final answer:
The program requires a programming language that supports graphics and key event handling; by using JavaScript and HTML5 canvas or a Python library like Pygame, one can manipulate the size of a red circle starting with a radius of 49 at coordinates (199, 199). Pressing 'D' decreases the radius by 10, while 'I' increases it.
Step-by-step explanation:
To create a program that responds to key events to manipulate the size of a red circle, you would need to use a programming language that supports graphics and event handling such as JavaScript with HTML5 canvas, or Python with a library like Pygame. The initial circle will begin with a radius of 49 and will be positioned at coordinates (199, 199). When the user presses the 'D' key, the circle's radius should decrease by 10, and when the 'I' key is pressed, the radius should increase by 10.
An example of how this could be achieved using JavaScript and HTML5 canvas might be as follows:
var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext('2d');
var radius = 49;
function drawCircle() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.beginPath();
ctx.arc(199, 199, radius, 0, Math.PI * 2);
ctx.fillStyle = 'red';
ctx.fill();
}
drawCircle();
document.addEventListener('keydown', function(event) {
if(event.key === 'd') {
radius = Math.max(0, radius - 10);
} else if(event.key === 'i') {
radius += 10;
}
drawCircle();
});
The JavaScript code sets up a drawing context on an HTML5 canvas, defines a function to draw the circle, and adds an event listener for key presses. The event listener checks if the 'D' or 'I' key is pressed, adjusts the radius accordingly, and then calls the function to redraw the circle with the new size.