Picasso likely never dreamed of the kinds of tools a computer can offer. From those raised on computers to strict physical medium traditionalists, hardware and software combinations for computers open compelling options for drawing. Using a tablet, mouse or touch screen, you can recreate the drawing process in programs like Adobe Photoshop, Microsoft Paint and others.
The Easiest Solution
Virtually every computer comes equipped with a native, or free, drawing solution. For Windows 8, that program is the free Fresh Paint (see Resources). Once you've downloaded it, you can use your mouse to draw on a white screen. Click, or tap and hold down while dragging in order to paint lines. Use the settings at the top of the program to change the style and color of brush. In earlier versions of Windows, a program came already installed and was simply called "Paint."
Professional Painting Programs
You'll find that native and free computer-painting solutions usually lack advanced features. Many programs are available for purchase that give you more tools for painting as well as greater control over the finished image. Adobe Photoshop provides a multitude of tools for both photo-editing and painting, but its complexity means the learning curve can be fairly steep. Corel's Painter X3 seeks to accurately reproduce the behavior of physical media in a digital environment, easing the transition for a traditional artist.
Physical Tools for Digital Drawing
Even with good software, it can be difficult to draw using a mouse or trackpad. To this end, a drawing tablet can be connected to a computer. Most such tablets allow you to "draw" with a pen-like stylus that moves your cursor across the screen as you pass it over the specially-designed pad. In addition to more fluid control, tablets such as the WACOM Intuos or VT PenPad can detect how hard you are pushing on the pen, and change the "flow" of digital paint accordingly. This results in smoother, more organic strokes.
Drawing Directly on Screen
The problem with mice and external tablets is that you are not looking at your hand as you draw or paint. To fix this, certain drawing pads and touch screens allow you to draw directly on your workspace, the same as if it were a piece of paper. The iPad enables this, but its capacitive touchscreen cannot detect how much pressure is being applied. Microsoft's Surface Pro uses Wacom technology with pressure sensing. Wacom also makes the Cintiq, a drawing pad that can be connected to any computer and replicates your computer screen as you draw on it.