Software Development and Software Engineering

Lecture 13 - February 3rd, 2017

Software is being integrated into everythnig we own
- coffee makers
- refrigerators
- cars
- airplanes

"The cost to fix an error found after product release was four to five times as much as one uncovered during design, and up to 100 times more than one identified in the maintenance phase."
- If a bug is found in the requirements-gathering phase, the cost could be $100.
- If the product owner doesn't
A 2003 study commisioned by the Department of Commerce's National Institure of Standards and Technology found that software bugs cost the US economy $59.5 billion annually.
- AND that was almost 15 years ago!

Software Engineering is...
- Discipline that applies theories, methods, and tools to solve problems related to software production and maintance
- Software engineers strive to deliver high- quality software that satisfies users’ needs, on time and within budget

Why is software engineering an important discipline?

What are some of the main challenges in developing software?

Software that remains useful over time, will
- continually change...
- become more complex
- increase in size
- decrease in quality

Free Puppy = Free Software

Term coined in 1968 due to The Software Crisis!
- "The major cause of the software crisis is that the machines have become several orders of magnitude more powerful! To put it quite bluntly: as long as there were no machines, programming was no problem at all; when we had a few weak computers, programming became a mild problem, and now we have gigantic computers, programming has become an equally gigantic problem.” Edsger Dijkstra, 1972
Still debated a bit what the term "software engineering" means!

"there is no single development, in either technology or management technique, which by itself promises even one order of magnitude [tenfold] improvement within a decade in productivity, in reliability, in simplicity.“ Fred Brooks, 1986
Difference between essential complexity

Brook's Law: "adding manpower to a late software project makes it later."
Watch for the "second system effect."
The tendency towards irreductible number of errors
Question:
- How does a large sofware project get to be one year late?
- One day at a time!
Always design a system to throw away
"good" programmer are generally five to ten times as productive as mediocre ones.

More fin grained steps

Flowchart from Slide

Waterfall Model

Water model in practice

Characteristics:

Every programmers has their own version of the code, which they work on on their own computer.
Changes are synchronized with a version control program like git
Programmers integrate code changes often, even several times a day
Communication is facilitated through:
- source code
- test cases
- system structure
- use case scenarios
- task estimation
Pair Programming:
- Two programmers work together at one computer
  - Observer/Navigator
    - strategize over direction
    - think of improvements
    - see likely future problems to address
    - bigger picture
  - Driver
    - actually writes the code
    - more details oriented
  - Switch roles often to prevent fatigue, leep interest
  - More man power BUT less code defects
  - Great learning experience
  - Better for complex task
Software Testing:
- Every line of code is tested (in practice, impossible)
- Test -> while coding, before coding
Ethics...
- ACM/IEEE Software Engineering Code of Ethics and Professional Practice
- Eight Priniciples

Ethical Dilemmas?

Open Source:

Things to think about:

How is software engineering different from other kinds of engineering (e.g. civil, mechanical, electrical etc)?
How is software engineering different from computer science?

Summary

Software engineering is an exciting field!
Combines elements of engineering, computer science, social sciences, business, management....
Can be interdisciplinary
Is an important profession! Software engineers are in high demand!