Software Engineering is a technological and managerial discipline concerned with systematic production and maintenance of software products that are developed and modified on time. The primary goal of software engineering are to improve the quality of software products and to increase the productivity and job satisfaction of software engineer.    Software development life cycle(SDLC): Software is said to have life cycle composed of several phases . 1. Feasibility study 2. Requirement analysis and specification 3. Design 4. coding 5. Testing 6. Implementation 7. Maintenance                       In comparison coding takes less time while testing takes very much time. Testing includes independent person , quality, time ana effort. Ojective: of software engineerinf is to produce high Quality software at low economical cost. Software characteristics : 1. Software are engineered or developed not manufactured. 2. Software does not wear out. 3. All the software are custom build Software Application: 1. System software eg compiler , editor 2. Bussiness Software eg payroll , trading 3. Scientific and engineering software eg eye testing 4. Artificial Intelligence software eg robot 5. PC software