Abstract This thesis mainly discusses D.C. functions. In the opinion of J.B. Hiriart-Urruty﹝2﹞, there are five interesting problems concerning D.C. functions: 1. Basic properties of D.C. functions. 2. How to characterize a D.C. function? 3. How to decompose a D.C. function? 4. Optimality conditions, duality for D.C. function. 5. Preview on minimization procedures for D.C. functions. The main purpose of this report is based on recognizing a D.C. function. After introducing the definitions of convex functions and functions of bounded variation on the real line, we investigate furtuer the characteristic of convex functions and functions of bounded variation. Then, we find the relationships among convex functions, function of bounded variation D.C. functions. Key words: convex function, convex analysis, D.C. function, function of bounded variation.