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How to use Methods in Java
Methods and Parameters in Java
Creating User-Defined Methods
Common Programming Errors
Good Programming Practices
Lab Exercises
Labs 1
Labs 2
Rubric

Defining Our Own Subroutines

Description

This activity builds on students’ knowledge of variables and subroutines. Through a series of discussions, demonstrations, and lab exercises, students learn to make the distinction between local and global variables as they relate to variable parameters in programmer-defined subroutines.

Strand(s) & Learning Expectations  

Strand(s): 

A. Programming Concepts and Skills  B. Software Development  C. Computer Environments and Systems  D. Topics in Computer Science

Planning Notes

• Gather samples of built-in subroutines for identification of functions vs. procedures and for identification of parameters.

• Provide and demonstrate syntax required for writing programmer-defined subroutines in the language of choice.

• Provide on-line and/or print resources for shared use by students.

• Provide examples that help students understand variable scope and the passing of parameters as information to parts of the program. Students often have difficulty with variable scope and parameter passing.

• Review variable naming conventions and/or adopt conventions that identify the scope of a variable.

Prior Knowledge & Skills

Students:

• can demonstrate appropriate use of built-in subroutines;

• are able to debug programs containing syntax and logic errors.

Teaching/Learning Strategies

• Discuss with students the concept that a subroutine (function or procedure) often needs data in order to complete its task. Data is given (passed) to a procedure by enclosing it in parentheses in the procedure call.

• Assign students the task of identifying the required parameters for a series of selected functions and procedures, making connections to math and text subroutines explored in Activities 2 and 3.

• Discuss the concept of variable scope and the need for parameters to pass information from one component to another.

• Facilitate a brainstorming session to write an algorithm for a modular program that reads (input) a customer’s bank balance then, if the balance is less than zero, prints an “Overdraft” notice, or else interest is calculated (based on current rate) and added to the original balance.

• Promote use of subroutines to divide tasks, identifying required parameters for each subroutine.

• Introduce the concept that the parameters for balance and interest are considered variable parameters because their values are changed by the Calculate subroutine, while the rate parameter is not a variable parameter because its value is not changed by the Calculate subroutine.

• Demonstrate the syntax for defining a custom subroutine in your programming language.

• Student record new tools and strategies in a journal or notes.

• Student complete as many lab exercises as possible in time allotted. (See Lab Exercises, Labs 1, Labs 2)

Assessment & Evaluation of Student Learning

As Learning

Students will be given time to:

• reflect on their progress/ understanding/areas of concern based on teacher/student/peer suggestions (e.g. after test take up)
• journalize their reflections
• reflect on the work of others

For Learning

The teacher will

• observe student progress/performance
• ask questions based on student work
• check homework correctness/completion when appropriate
• review formative quiz results

Of Learning

The teacher and students gather assessment information based on specific expectations outlined for this activity, including:

• a formative assessment of the assigned work in the form of roving conferences;

• a formative assessment of the journal/notebook (checking for inclusion of tools/strategies presented);

• a summative assessment of the student’s ability to describe parameter passing and scope and identify differences between local and global variables. Students break down computer tasks into specific functions and define the modules, parameters, and variables used.

Accommodations

The following are ways in which the activity can be adapted to accommodate the exceptional students’ needs:

• support brainstorming activity through use of web or mapping chart with print copy;

• provide support through one-to-one teacher-directed conferencing to ensure understanding;

• provide “scaffolded” programs (program listings with subroutine headings, loop structures, etc., already included) to help struggling students.

Resources

• Installed help files and/or manuals for the programming language in use.

• How to use Methods in Java (Appendix 3.3.1)

• Methods and Parameters in Java (Appendix 3.3.2)

• Creating User-Defined Methods (Appendix 3.3.3)

• Common Programming Errors (Appendix 3.3.4)

• Good Programming Practices (Appendix 3.3.5)

• Lab Exercises (Appendix 3.3.6)

• Labs 1 (Appendix 3.3.7)

• Labs 2 (Appendix 3.3.8)

• Rubric (Appendix 3.3.9)

Source: Public and Catholic District School Board Writing Partnership,  Course Profile: Computer and Information Science, Grade 11, University/College Preparation ICS3U, Queen’s Printer for Ontario, 2001, adapted.