CSC 1029 Week 05: Software Development Lifecycle

CSC 1029 Week 05 Class Session

• Topic: Responsible Software Development
• Sections: The Software Development Lifecycle

Learning Objectives

• Students will describe the security development lifecycle (SDL).
• Students will illustrate the analysis phase of the software development lifecycle (SDLC) for simple problems.
• Students will recognize the three basic control structures.

Overview

• Topics: Software development lifecycle (SDLC), Security development lifecycle (SDL), Programming languages, Structured programming, Defining the problem

Software Development Lifecycle (SDLC)

• Step 1: Define the problem (analysis)
• Step 2: Design the solution (algorithm)
• Step 3: Code solution (program)
• Step 4: Test and debug
• Step 5: Maintain and document

Software Development Lifecycle (continued)

• Phases: Analysis, Design, Implement, Test, Maintain

Security Development Lifecycle (SDL)

• SDL takes each element of the software development lifecycle (SDLC) and considers how it pertains to security.
• Each phase of the SDL considers security.

Analysis

• WHAT?: Defining the problem, Requirements, Most common cause of software failures is poor requirements gathering, Generate and document a clear problem statement, Use IPO diagram, Consider security

Design

• HOW?: Planning, Algorithm—expansion of steps in the IPO diagram, Flowchart, Pseudocode, Consider security

Design Tools

• Pseudocode: Can be easily done on a word processor, Implements structured design elements well, Not visual, No standard
• Flowchart: Standardized, Visual, Difficult to modify, Requires special software to do on computer

Flowchart and Pseudocode

• Example of both flowchart and pseudocode are provided depicting input of pay rate and hours worked, calculating net pay, and outputting net pay

Algorithm

• Step-by-step procedures for solving a problem in a finite amount of time.
• Computer is a tool to implement algorithms.
• Algorithm is an ordered set of instructions with finite steps, takes finite time, precise steps, and solves a general class of problems.

Implement

• Choose language, Edit—create source program, Code responsibly, Compile (translate) and Link, Syntax error—violation of programming language rules, Compiler error messages, Example: semicolon missing from programming language statement

Implement (continued)

• Create an executable program.
• Consider security.

Structured Programming

• Top-down Design—divide and conquer
• Modularity, Subprograms, Stepwise refinement
• The Structure Theorem—use three basic control structures to solve any problem:
  • Sequence
  • Selection (if-then-else)
  • Repetition (loop)

Basic Control Structure 1: Sequence

• Statement, Statement, Statement

Basic Control Structure 2: Selection (Branch)

• IF condition THEN Statement1 ELSE Statement2
• Example: If (num > 0) Display "Positive" Else Display "Negative"

Basic Control Structure 3: Repetition (Loop)

• WHILE condition DO Statement1

Subprogram (Function)

• Meaningful collection of sequences, selections, loops, and subprograms.

Test and Debug

• Test with variety of data.
• Debugging: locating and correcting errors
  • Logic error, flaw in the algorithm
  • Run-time error (e.g., divide by zero)
• Programming packages usually have debugger software to help programmers.
• Consider security.

Maintain and Document

• Maintenance—changing and maintaining existing programs.
• Most coding is actually maintenance.
• Documentation—sometimes done by technical writers.
• Reliable documentation is a must.
• Helps keep track of all aspects of an application.
• Makes complex programs easier to read and understand.
• Key in knowledge transfer.
• Consider security.

Example charts for steps in software development lifecycle

• Examples of IPO chart tables and their elements, and several examples (Example 1 to 4) for practice exercises.
• Example charts are included to practice identifying the input, process, and output for solving problems to construct computer programs.

Computing Profession Ethics

• Copy software only with permission.
• Give credit to programmers.
• Use computer resources only with permission.
• Guard confidential data.
• Use software engineering principles to make error-free programs.

This quiz covers the Responsible Software Development topic, focusing on the Software Development Lifecycle (SDLC) and the Security Development Lifecycle (SDL). Students will learn the phases of the SDLC, including analysis, design, coding, testing, and maintenance, while also recognizing basic control structures essential in programming.