week08

Interface Prototypes Logic Prototypes System Sketches Incremental Implementation
CSE2200 - System Design and Implementation
Lecture 8
Interface Prototype
Test the usability of the system’s intended interface Requires a working system “underneath” Should determine the
Cost of learning the system Cost of using the system
Note that these are very different issues!
CSE2200 - System Design and Implementation
Lecture 8
Logic Prototype
Test the analyst/designers’ understanding of the users’ requirements As such, must happen early in the analysis phase Important phase of analysis when the users are experts at their tasks and not able to articulate requirements.
only do this with array storing primitive types
int result = myArray[3] + myArray[4] ; // result = 300 int my2DArray[3][5]; int x = my2DArray[1][1] + my2DArray[2][5]; Arrays start with element 0 (zero) Array indexes must be of type int
CSE2200 - System Design and Implementation
Lecture 8
Human Expertise
Know what -- that knowledge that can be consciously retrieved anБайду номын сангаас articulated. Typically “book learning” Know how -- skill-based knowledge which is skillthe basis of expert performance without much conscious thought. The result of experience. This is a critical distinction of great importance in prototyping.
CSE2200 - System Design and Implementation
Lecture 8
Variables and Data Types
Variable declaration
int x; int y = 100; data type variable_name (assignment)
CSE2200 - System Design and Implementation
Lecture 8
Operators
Commonly Used Java Operators
+ : addition - : subtraction * : Multiplication / : Division = : Assignment += Assign and sum && : Logical AND || : Logical OR == : Equal to != : Not equal to ++ : Increment x = y + z; x = y - z; x = y * z; x = y / z; x = 10; x += 10; (same as x = x + 10) if (x && y) {…} if (x || y) {…} if (x == 10) {…} if (x != 10) {…} x++; (same as x := x + 1;)
CSE2200 - System Design and Implementation
Lecture 8
Arrays
An array is a collection of values of a particular data type int myArray[ ]; // declares the array myArray = new int[5]; // creates the Array object int myArray[ ] = { -200, -100, 0, 100, 200 };// creates the Array with an implied new
CSE2200 - System Design and Implementation
Lecture 8
What is prototyping?
The development of a system and/or the requirements of the system by the means of building a partial ‘working’ version of the ‘working’ system Advantages
defining requirements is easier users and developers see actual progress from an early stage
Disadvantages
users see what appears to be a real system early on, creating false expectations implementation compromises are made to get the prototype working, which carry over to the final system CSE2200 - System Design and Implementation Lecture 8
CSE2200 - System Design and Implementation
Lecture 8
Incremental Implementation
System prototyped and developed in chunks Prototypes put into production use as implemented Assumes
Boolean - true or false byte (-128 to 127) (short (32,768 to 32,767) char (16 bit Unicode characters) int (-2,147,483,648 to 2,147,483,647) (long (-263 to 263-1 integers) (float (+/- 1039 floating point) (+/double (+/-10317 floating point) (+/-
CSE2200 - System Design and Implementation Lecture 8
Programming Constructs
IF if (condition) { true statements; } else{ false statements; } FOR LOOP for (initial; condition_expression, adjustment) { statements; } BREAKING OUT OF LOOPS break; CSE2200 - System Design and Implementation
CSE2200 - System Design and Implementation
Lecture 8
Prototyping as Requirements Elicitation
Expertise is hard to access Experts find it difficult to articulate their expertise Prototypes (that work) throw the experts into their normal tasks The expertise may well emerge Note that this approach is not appropriate where Know What needs to be accessed and the expert is perfectly capable of articulating the system requirements. EG, most accounting systems
CSE2200 - System Design and Implementation Lecture 8
Review of Java Basics
Variables and Data Types Operators Arrays Programming Constructs Classes Scope Strings
Variable names are CASE-SENSITIVE! CASECSE2200 - System Design and Implementation Lecture 8