Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software, and the study of these approaches. That is the application of engineering to software.
The term software engineering first appeared in the 1968 NATO Software Engineering Conference and was meant to provoke thought regarding the current "software crisis" at the time. Since then, it has continued as a profession and field of study dedicated to creating software that is of higher quality, cheaper, maintainable, and quicker to build. Since the field is still relatively young compared to its sister fields of engineering, there is still much work and debate around what software engineering actually is, and if it deserves the title engineering. It has grown organically out of the limitations of viewing software as just programming. Software development is a term sometimes preferred by practitioners in the industry who view software engineering as too heavy-handed and constrictive to the malleable process of creating software.
Yet, in spite of its youth as a profession, the field's future looks bright as Money Magazine and Salary.com rated software engineering as the best job in America in 2006. 
See main article: History of software engineering. While the term software engineering was coined at a conference in 1968, the problems that it tried to address started much earlier. The history of software engineering is inextricably intertwined with the dueling histories of computer hardware and computer software.
When the modern digital computer first appeared in 1941, the instructions to make it operate were wired into the machine. Practitioners quickly realized that this design was not flexible and came up with the "stored program architecture" or von Neumann architecture. Thus the first division between "hardware" and "software" began with abstraction being used to deal with the complexity of computing.
Programming languages started to appear in the 1950s and this was also another major step in abstraction. Major languages such as Fortran, Algol, and Cobol were released in the late 1950s to deal with scientific, algorithmic, and business problems respectively. E. W. Dijsktra wrote his seminal paper, "Go To Statement Considered Harmful",  in 1968 and David Parnas introduced the key concept of modularity and information hiding in 1972 to help programmers deal with the ever increasing complexity of software systems. A software system for managing the hardware called an operating system was also introduced, most notably by Unix in 1969. In 1967, the Simula language introduced the object-oriented programming paradigm.
These advances in software were met with more advances in computer hardware. In the mid 1970s, the microcomputer was introduced, making it economical for hobbyists to obtain a computer and write software for it. This in turn lead to the now famous Personal Computer or PC and Microsoft Windows. The Software Development Life Cycle or SDLC was also starting to appear as a consensus for centralized construction of software in the mid 1980s. The late 1970s and early 1980s saw the introduction of several new Simula-inspired object-oriented programming languages, including C++, Smalltalk, and Objective C.
Open-source software started to appear in the early 90s in the form of Linux and other software introducing the "bazaar" or decentralized style of constructing software  . Then the Internet and World Wide Web hit in the mid 90s changing the engineering of software once again. Distributed Systems gained sway as a way to design systems and the Java programming language was introduced as another step in abstraction having its own virtual machine. Programmers collaborated and wrote the Agile Manifesto that favored more light weight processes to create cheaper and more timely software.
The current definition of software engineering is still being debated by practitioners today as they struggle to come up with ways to produce software that is "cheaper, bigger, quicker".
See main article: Software engineer.
While some areas, such as Ontario, Canada , license software engineers; most places in the world have no laws regarding the profession of software engineers. Yet there are some guides from the IEEE Computer Society and the ACM, the two main professional organizations of software engineering. The IEEE's Guide to the Software Engineering Body of Knowledge - 2004 Version or SWEBOK defines the field and gives a coverage of the knowledge practicing software engineers should know. There is also an IEEE "Software Engineering Code of Ethics".  In addition, there is a Software and Systems Engineering Vocabulary (SEVOCAB) , published on-line by the IEEE Computer Society.
In 2004, the U. S. Bureau of Labor Statistics counted 760,840 software engineers holding jobs in the U.S.; in the same time period there were some 1.4 million practitioners employed in the U.S. in all other engineering disciplines combined. Due to its relative newness as a field of study, formal education in software engineering is often taught as part of a computer science curriculum, and as a result most software engineers hold computer science degrees.
Most software engineers work as employees or contractors. Software engineers work with businesses, government agencies (civilian or military), and non-profit organizations. Some software engineers work for themselves as freelancers. Some organizations have specialists to perform each of the tasks in the software development process. Other organizations require software engineers to do many or all of them. In large projects, people may specialize in only one role. In small projects, people may fill several or all roles at the same time. Specializations include: in industry (analysts, architects, developers, testers, technical support, managers) and in academia (educators, researchers).
There is considerable debate over the future employment prospects for Software Engineers and other IT Professionals. For example, an online futures market called the "ITJOBS Future of IT Jobs in America" attempts to answer whether there will be more IT jobs, including software engineers, in 2012 than there were in 2002.
Professional certification of software engineers is a contentious issue. Some see it as a tool to improve professional practice;"The only purpose of licensing software engineers is to protect the public" 
The ACM had a professional certification program in the early 1980s, which was discontinued due to lack of interest. The ACM examined the possibility of professional certification of software engineers in the late 1990s, but eventually decided that such certification was inappropriate for the professional industrial practice of software engineering., the IEEE had certified over 575 software professionals. In Canada the Canadian Information Processing Society has developed a legally recognized professional certification called Information Systems Professional (ISP).
Most certification programs in the IT industry are oriented toward specific technologies, and are managed by the vendors of these technologies. These certification programs are tailored to the institutions that would employ people who use these technologies.
Many students in the developed world have avoided degrees related to software engineering because of the fear of offshore outsourcing (importing software products or services from other countries) and of being displaced by foreign visa workers. Although government statistics do not currently show a threat to software engineering itself; a related career, computer programming does appear to have been affected.  Often one is expected to start out as a computer programmer before being promoted to software engineer. Thus, the career path to software engineering may be rough, especially during recessions.
Some career counselors suggest a student also focus on "people skills" and business skills rather than purely technical skills because such "soft skills" are allegedly more difficult to offshore. It is the quasi-management aspects of software engineering that appear to be what has kept it from being impacted by globalization.
A knowledge of programming is the main pre-requisite to becoming a software engineer, but it is not sufficient. Many software engineers have degrees in Computer Science due to the lack of software engineering programs in higher education. However, this has started to change with the introduction of new software engineering degrees, especially in post-graduate education. A standard international curriculum for undergraduate software engineering degrees was defined by the CCSE.
In 1998, the US Naval Postgraduate School (NPS) established the first doctorate program in Software Engineering in the world. Steve McConnell opines that because most universities teach computer science rather than software engineering, there is a shortage of true software engineers. In 2004 the IEEE Computer Society produced the SWEBOK, which has become an ISO standard describing the body of knowledge covered by a software engineer .
Software engineering can be divided into ten subdisciplines. They are:
The building of a software system is usually considered a project and the management of it borrows many principles from the field of Project management.
Systems engineers have been dealing with the complexity of large systems for many decades and their knowledge is applied to many software engineering problems.
. Roger S. Pressman. Software Engineering: A Practitioner's Approach. 6th ed.. 2005. McGraw-Hill. Boston, Mass. 0072853182.
. Pankaj Jalote. An Integrated Approach to Software Engineering. 1991. 3th ed.. 2005. Springer. 0-387-20881-X.