Direct Changeover: This involves completely replacing the old system with the new system overnight.

Characteristics: The old system is decommissioned immediately after the new system is installed. All data is migrated at the same time.

Benefits: It's the quickest and potentially cheapest method in the short term. There's no period of running both systems.

Drawbacks: It's the riskiest method. If there are problems with the new system, the entire organization is affected immediately, potentially leading to significant disruption and data loss. Requires extensive testing beforehand.

Parallel Running: The old and new systems run simultaneously for a period.

Characteristics: Both the old and new systems are used to process data. Data is compared to ensure accuracy.

Benefits: Minimizes disruption as users can continue using the familiar old system if problems arise with the new one. Allows for thorough testing and validation of the new system.

Drawbacks: It's the most expensive method as it requires maintaining two systems concurrently. It can be complex to manage and requires significant resources.

Pilot Running: The new system is implemented in a limited area or with a small group of users before being rolled out to the entire organization.

Characteristics: A controlled environment for testing and identifying issues. Feedback is gathered from pilot users.

Benefits: Allows for early identification and resolution of problems before a full-scale rollout. Reduces the risk of widespread disruption. Provides valuable user feedback.

Drawbacks: The pilot group may not be representative of the entire organization, so issues identified in the pilot may not occur in the wider implementation. Can delay the overall implementation process.

Phased Implementation: The new system is implemented in stages, with different parts of the organization or different functions using the system at different times.

Characteristics: Allows for a gradual transition to the new system. Each phase can be tested and refined before the next phase begins.

Benefits: Reduces disruption by limiting the impact of any problems to a specific area. Allows for better resource allocation and training.

Drawbacks: Can be more complex to manage than direct changeover. Requires careful planning and coordination between phases. May require temporary integration between the old and new systems during the transition periods.

Here are three types of test data a developer could use for a login form:

1. Valid Username and Password: This is the baseline test. It verifies that the login form correctly authenticates users with legitimate credentials. It's important to ensure the core login process works as intended. Failure here indicates a fundamental problem with the authentication logic.
2. Invalid Username and Valid Password: This tests the username validation. It checks if the system correctly rejects incorrect usernames while allowing users with valid passwords to log in. It reveals issues with username format validation or database lookup.
3. Valid Username and Invalid Password: This tests the password validation. It verifies that the system correctly rejects users with incorrect passwords while allowing users with valid usernames to log in. It reveals issues with password matching algorithms or password storage.

Validation routines are essential to ensure the accuracy and reliability of data entered into the student grade management program. Here are some necessary validation routines:

• Input Validation: Checks that the user has entered data in the correct format. For example, ensuring that grades are entered as numbers (e.g., 0-100) and not as text. This can involve using regular expressions or other parsing techniques.
• Range Checking: Verifies that the entered grades fall within acceptable ranges. For example, ensuring that a grade is not below 0 or above 100. This prevents invalid data from being stored.
• Data Type Validation: Ensures that variables are of the correct data type. For example, ensuring that the number of attempts is an integer.
• Required Field Validation: Checks that all required fields are filled in. For example, ensuring that a student's name and ID are entered.
• Duplicate Entry Validation: Prevents the creation of duplicate student records.

Sample Run for Testing Validation Routines:

1. Run the program.
2. Attempt to enter a grade of -50. The validation routine should prevent this and display an error message.
3. Attempt to enter a grade of 110. The validation routine should prevent this and display an error message.
4. Attempt to enter a grade of "A". The validation routine should prevent this and display an error message.
5. Attempt to save the program with a missing student ID. The validation routine should prevent this and display an error message.
6. Attempt to save the program with a duplicate student ID. The validation routine should prevent this and display an error message.

By carefully designing and testing these validation routines, the program can ensure that the student grade data is accurate and reliable.