In a Numerical Control machine, the program is fed to the machine through magnetic tapes or other such media. The original NC machines were essentially basic machine tools which were modified to have motors for movement along the axes. CNC machines
In a Computer Numerical Controlled machine, the machines are interfaced with computers. This makes them more versatile in the sense that, suppose a change in dimension of a part is required. In a NC machine, you would have had to change the program in the tape and then feed it to the machine again. But in a CNC machine, you just change a variable in the computer and your modification is done!!
Read more: http://wiki.answers.com/Q/Difference_NC_and_CNC#ixzz27yxVbWo3
The input device is any machine that feeds data into a computer. The input devices are:
i)- Keyboard:- Keyboard is an input device consisting of a set of typewriter keys that enable us to enter data into a computer. Computer keyboard are similar to electric typewriter. Keyboard has the following keys.
Alphabetic keys (A to Z, a to z) Alphanumeric keys (0 to 9).
Special keys. Functions keys, control keys, arrow keys caps lock key, and so on.
ii). Mouse:- Mouse is a device that controls the movement of the curser or pointer on a display screen. A mouse is a small object we can roll along a hard flat surface. As we move the mouse the pointer on the display screen moves in the same direction.
iii). Joystick:- A lever that moves in all directions and controls the movement of a pointer or some other display symbols. A joystick is similar to a mouse except that with a mouse the cursor stops moving as soon as we stop moving the mouse. With a joystick the pointer continuous moving in the direction the joystick is pointing. Joysticks are used mostly for computer games but that are also used occasionally for CAD/CAM systems and other applications.
iv). Scanners:- Scanner is an input device that can read text or Picture printed on paper and translates the information into a form that the computer can use. A scanner works by digitizing an image dividing it into a grid of boxes and representing each box with either a zero or a one. We can send the picture or other images to compute.
v). Digital Camera:- Images can be input into a computer using a digital camera. These images can then be manipulated in many ways using the images tools. The digital camera takes a still photograph, stores it and then sends it as digital input the computer. The images are then stored as digital files.
vi). Bar Code Reader: The bard code identifies the product to the supermarkets, computers, which has a description and the latest price of the product the computer automatically tells the point of sales terminal what the price is.
vii). Light Pen. Light pen is an input device that utilizes a light sensitive detector to select objects on a display screen. A light pen is similar to a mouse except that with a light pen we can move the pointer and select objects on the display screen by directly pointing to the objects with the pen.
- An output device is any machine capable of representing information forms a computer. Output devices include display screens, loudspeakers, printers, plotters etc.
i). Monitor: Monitor is displays output. We can see the result by monitor. It is look like a T.V screen. There are many ways to classify monitors. The most basic is in terms of color capacities separates monitors into three classes.
Monochrome: Monochrome monitors actually display two colors, one for the background and one for the foreground. The colors can be black and white, green and black or amber and black.
Color: Color monitors can display anywhere from 16 to over I million different colors it is also called RGB monitors because they accept three separate signals red, green, and blue. An RGB monitor consists of a vacuum tube with three...