College Board 1.3 1.4 - LindaLiu1202/lindaliu GitHub Wiki

College Board 1.3.1 Video Notes

How is a program developed?
- Programs are developed with a specific function in mind
- Developers follow specific steps and follow through with them
  - Sometimes development can be more exploratory
- Developers start investigating the problem/purpose and reflect
  - Investigation is important (surveys, user testing, interviews, direct observations)
  - Developers: determine the requirements of the program, understand the constraints, and understand the user concerns and interests
- After initial investigation and reflection:
  - Developers design the program by: brainstorm, storyboard the program, plan user experience, lay out user interface, organize into modules, develop testing strategy
Developers decide program requirements that list user interactions and describe how a program should behave
Program specifications outline all program requirements
Developers create a prototype of the program
- Incremental process frequently used by developers so that they can work in small increments then test
- Testing occurs at micro and macro levels, at every step of the development

Program development is rarely a solo endeavor
- Usually developed by teams of people
- Individuals/teams work on different functional components
- Each member of the project deserves to receive credit for their work
- Their names must be written in the documentation of the program indication their contributions to the project
While documentation is an important place to give credit:
- Many project use comments within the programming language to give credit
- This is an important part of the development of the program
- When developers find a bug they need to be able to determine who can/should fix the problem
- This may not be most useful after a program is completed and users find additions bugs
Many times developers use code segments, procedures, algorithms, and more that are written by others
- These other individuals are not necessarily a part of the project, but they still deserve to be credited
  - This is similar to quoting someone in a research paper or article
- Any code segments, procedures, algorithms, are considered intellectual property of the author
- The program documentation should include the author’s name and the source of any code segment being used
- This portion of the documentation may resemble a bibliography or a works cited page in a research paper

Programmers create something called program documentation in order to:
- Describe the overall program
- List program specifications
- Describe functions, procedures, methods with the code, code segments, lists of events/corresponding outputs, development of the program, how other programs interact with the program
- List of contributors and authors of the program
Documentation happens throughout the development process of the program:
- At the beginning - list specification
- During - to keep track of process
- After - to explain the overall process
Documentation throughout can improve:
- Efficiency of overall programming process
- Programmer’s ability to test and refine the program
- Programmer’s response to bugs
Most programming languages offer a commenting feature, although some do not
- Commenting allows programmers to write text within the program
- This text doesn’t affect the program
- Comments are for programmers to read
- This is a form of documentation and can be very useful when programmers collaborate or work individually
Text languages:
- Python: #comments appear on lines that follow the pound symbol
- Java: //comments appear on single line after the double forward slashes

Programmers are constantly running into errors when they program
- In fact, its an explanation that errors are a part of the programming process
- Proficient programmers can identify errors as one of the following types:
  - Logic error
  - Syntax error
  - Run-time error
  - Overflow error
Logic Error:
- This error is caused by the programmer making a mistake in the algorithm, which causes the program to behave unexpectedly
Syntax error:
- This is a mistake when a programmer makes a typo or writes some code that doesn’t follow the rules of the language
- Syntax errors cause the program to fail to run/compile
- Common examples are: colon, semicolon, parenthesis, curly braces, indentation, quotes, variable definitions
Run-time error:
- When a program fails in the midst of running
- This error is commonly referred to as a bug
- The key to identifying this error is that the program runs/compiles initially, but fails and cannot complete its process
- May result from: dividing by zero, inappropriately entered data type
Overflow error:
- When a program is required to perform a calculation that’s outside of defined value range
- Due to memory allocation constraints that programming languages require, certain values are too big to calculate and/or display

The easiest error to correct is usually the syntax error
- Most integrated development environments display information when there is a syntax error
- This information usually directs the programmer to the line in the program where the error occurred
- Sometimes the user needs to do a little digging to find the error
The more difficult errors to find/correct are logic errors
- A logic error isn’t always immediately noticed
- Using test cases is the first strategy programmers use to find logical errors
Hand tracing can be most useful with iteration
- Hand tracing is simply writing out the values of the variables within the loop as it iterates to determine if the outcome is correct
- Can be useful for small code segments and loops that iterate a small number of times
- Larger code segments or loops might require a debugging program
Hand tracing shows us that the algorithm was actually just displaying the last time a number was less than the number after if in a list
A programmer would use this strategy to help find and fix an error
Once the error is corrected, the extra output statements are usually removed
This has a similar effect as hand tracing, but allows the computer to do more of the work

When do we start testing a program?
- Programs start testing on the onset of development
  - Or start thinking of testing
  - As soon as they know the specifications, they wonder how they know program is running
Specification Influence Testing:
- Recall program specifications list
- Programmers need to define the inputs to determine whether/whether not specifications were met
- Ex: algorithm designed to find minimum in a list
How does this influence program development?
- Once inputs/outputs are determined, the programmers test
- After testing, programmers refine to better the results
- Continue this process until they have the users test
- Once again refine and then release