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# CST 104 Lec 5

## Software Engineering

- engineering discipline that is concerned with all aspects of software production
- using approriate theories and methods to solve problems
- technical process of developement, project management, etc to support software production

## Software Products

### Generic vs Customized

| Types | Target | Examples | Software Changes |
| - | - | - | - |
| Generic | any customer | project management tools, CAD, etc | by the developer only
| Customized | specific customer | embedded control systems, etc | under customer request

## Software Costs

Software development often costs way more than hardware, this is due to frequent maintenance issues that require massive resources to resolve in the long term.

Hence, **implementing a cost-effective software development is crucial to build softwares that run cheaper in the long run.**

## Software Engineering Process

The formal process of developing large projects is facilitated through a clear 5 step approach:

flowchart LR;
Requirements --> Design --> Implementation --> Verification --> Maintenance

It requires collaboration and efficient management, where this principle is applied through **Softwaree Development Life Cycle (SDLC).**

## Software Development Life Cycle (SDLC)

Life cycles exist to maintain large-scale softwares:

### Before Implementation

**Feasibility Study**

- assess costs and benefits
- consider if the project is cost-effective
- consider alternatives
- create something from another way

**Problem Specification**

- statement of problems to be solved
- documentation of problems specified
- consider all scenarios

**Program Design Phase**

- **divide-and-conquer and decomposition approach**
- break into tasks and subtasks
- documentation of tasks graphically

**Algorithm Selection or Development and Analysis**

- design algorithm for each task
- analyze it's efficiency
- provide pseudocode and efficiency report

### Implementation

**Coding**

- translate pseudocode to working code

**Debugging**

Types of errors:

- **Syntax Errors: Grammatical errors in code**
- **Runtime Errors: illegal operations**
- exp: dividing by 0
- **Logic Errors: does not perform as expected**

### After Implementation

Testing, verification and benchmarking:

- **Emphirical Testing: test suite to check correctness**
- **Unit Testing: test each module/subtask**
- **Integration Testing: test how modules work together**
- **Regression Testing: test when changes are updated**

**Program Verification**

- Benchmarking: check performance on inputs

**Documentation**

Document each phase of the project along the process of engineering a software.

- **Internal:** comments in code
- **External:** everything during the phase before implementation
- **Technical:** information for programmers to understand the code
- **User:** helps users run programs

**Program Maintenance**

- add features, fix bugs and improve performance

## Integrated Development Environment (IDE)

IDE consists of these features to significantly speed up program development:

- program editor: create program
- file manager: store program
- compiler / interpreter: translate program to machine language
- debugger: help locate errors

**Rapid Prototyping**

GUI:

- shown to prospective users during initial stage of development
- allows any miscommunication between user and programmer to be resolved quickly

Software packages:

- track requirements from initial specification through the design process to final code
- version control system: track code versions

## Other Software Engineering Methodologies

### Agile Software Development

- problem specification doesn't exists
- change is expected and resolved in an agile way

## Software Engineering Diversity

Software engineering methods and tools **depend on the type of application being developed:**
- customer requirements
- development team background

## Application Types

### Standalone Software

- includes all necessary functionality
- can work offline

### Interactive or Online Transcation Processing System (OLTP)

- access and execute remotely
- web-based or remote systems
- exp: e-commerce applications, financial transcation systems

### Embedded Control Systems

- control and manage hardware devices

### Batch Processing Systems

- non-interactive systems
- process large data to create corresponding outputs

### Entertainment Systems

- handle graphics, audio, video, etc
- based on entertainment purposes

### Modeling and Simulation

- model physical process or situations
- interactive objects
- model and simulate system engineering

### Data Collection Systems

- collect data from an environment
- using sensors
- send data for analysis and processing

### Systems of systems

- composed of software systems
- collection of task-oriented systems to build a complex system
- system of systems engineering

## Software Engineering and The Web

**Web-based systems (complex distributed systems) and web services** allow application functionality to be accessed over the web. Fundamental software engineering principles still apply to web-based software

**Cloud Computing**

### Web Software Engineering

**Software reuse is the main approach to constructing web-based systems:**

- assemble from pre-existing software components and systems
- impractical to specify all requirements for such system

**User interfaces are constrained by the capabilities of web browsers**

- **AJAX** (difficult to use)
- local scripting are more commonly used

## Software Engineering Ethics

### Honesty and Ethics

Ethical behaviour is more than simply upholding the law:

- following a set of ethically principles that are morally correct

**Intellectual Property Rights**

- aware of local laws governing the use of intellectual
- ensure that the intellectual property of employers and clients is protected

**Computer Misuse**

- **must not use their technical skills to do harm**

### Ethical Dilemmas

**Red flags:**

- disagreement with the policies set by senior management
- unethical employer:
- releases safety-critical system without finishing tests
- participation in development of military weapons and nuclear systems

## ACM/IEEE Code of Ethics

**ACM/IEEE-CS Joint Task Force**

Professional socities in US cooperated to produce code practice:

> Software engineers should be committed to making the *analysis, specification, design, development, testing and maintenance of software a beneficial and respected profession* in accordance to the health, safety and welfare of the public, software engineers shall adhere to the **Eight Principles.**

- **PUBLIC - Software engineers shall act consistently with the public interest.**

- **CLIENT AND EMPLOYER - Software engineers shall act in a manner that is in the best interests of their client and employer consistent with the public interest.**
- **PRODUCT - Software engineers shall ensure that their products and related modifications meet the highest professional standards possible.**
- **JUDGEMENT - Software engineers shall maintain integrity and independence in their professional judgment.**
- **MANAGEMENT - Software engineering managers and leaders shall subscribe to and promote an ethical approach to the management of software development and maintenance.**
- **PROFESSION - Software engineers shall advance the integrity and reputation of the profession consistent with the public interest.**
- **COLLEAGUES - Software engineers shall be fair to and supportive of their colleagues.**
- **SELF - Software engineers shall participate in lifelong learning regarding the practice of their profession and shall promote an ethical approach to the practice of the profession.**

## Case Studies

Refer to PPT