Although every person has different writing style so it is very difficult for machine to recognize these characters. So, lots of researcher did a lot of work in this area and still going on to make it better. Image processing is an interesting and widely used field in the research area. Handwritten digit recognition is a sub module of the image processing. Although lots of research has been done so for in this field and continues. This paper suggested a novel approach of off-line handwritten digit recognition. The paper classified the digits into four regions: the left part, right part, upper part and lower part. In these four parts the images are identified on the basis of curve. The curve of a left part image is converted into pixels and as well as rest of all parts. Then these pixels are compared through decision tree and the result of comparison describes the format of digit. This application should help in zip code recognition, bank's cheque number recognition.