Introduction to Computing Technology PDLC (PDF)

Introduction to Computing Technology The Program Development Life Cycle Program Development (PDLC) (application software development) – The process of creating application programs Program Development Life Cycle (PDLC) – The five phases of progra...

Introduction to Computing Technology The Program Development Life Cycle Program Development (PDLC) (application software development) – The process of creating application programs Program Development Life Cycle (PDLC) – The five phases of program development Program Analysis  1- Problem During problem analysis, a systems analyst and Analysisand talk with users to programmer review specifications fully understand what the software should do. Documentation consists of: Program specifications, Timetable, Which language will be used, How the program will be tested, What documentation is required. 2-Program design  Program Design: Program Design Tools Program design tools are planning tools. 1. Program flowcharts 2. Pseudocode  Program Design:Program Design Tools Program flowcharts – use geometric symbols and familiar relational operators to provide a graphic display of the sequence of steps involved in a program. – The steps in a flowchart follow each other in the same logical sequence as their corresponding program statements will follow in a program. – Different symbols are used to represent different actions, such as start/stop, decision, input/output, processing, and looping symbols.  Example Example: Average of 10 Numbers – iteration with a while loop Begin i 0 = 0 sum i < while = input 10 x sum = sum + x Increment i avg = sum / 10.0 print avg End  Program Design: Program Design Tools Pseudocode uses English-like statements in plac of the graphic symbols of e the flowchart. Unlike a flowchart,pseudocode is easy modify and can be to embedded into a program as comments. No standard set of rules exists for writing pseudocode, although a  Pseudocode Write a pseudocode algorithm that computes the area of the circle Problem: Calculate and display the area of the circle Discussion: Uses mathematical knowledge, that is area = r2 Output: area of the circle Input: radius of the circle Processing: Find the area of the circle; area = 3.14 * radius * radius pseudocode algorithm Codin  3- PDLC- Program Coding Coding: actual process of creating the program in a programming language. Programming language must be chosen. Coding standards should be adhered to. Make use of reusable code and data dictionaries. Translate coded programs into executable code.  Progra m Coding The coded program is referred to as source code. to be executed, the program is converted by the computer to object code using a special program. A compiler translates the entire program into machine language before executing it. The program then doesn’t need to be recompiled until it is modified. An interpreter translates program statements one at a time. Interpreters are helpful during the debugging stage, but are slowerduringexecution of the 4- Debugging and testing  4- PDLC- Program Debugging and Testing Debugging: process of making sure a program is free of errors or bugs. Preliminary bugging often finds syntax or logic errors. Testing can consist of alpha or beta testing.  Program Debugging and Testing Preliminary debugging begins after the program has been entered into the computer system. Rarely is a program error- free the first time it runs. Two common types of errors are syntax errors and logic errors. – A syntax error: occurs when the programmer has not followed the syntax rules of the language. – A logic error, or execution-time error: results when the command syntax is correct but the program is producing incorrect results due to incorrect equation or design. –A run time error: occurs at running time of a program as e.g. dividing by zero or access not found Example of Syntax error Example of logic error Example of runtime error  Program Debugging and Testing At some point in the preliminary debugging process, the program will appear to be correct. At this point, the programmer, or preferably someone else, will run the original program with extensive test data. Good test data will subject the program to all the conditions it might conceivably encounter when finally companies implemented.in the business of selling software Most companies run also alpha tests run commonly on-site prelimina to test beta versions oftests programs; the program by distributing to outside ry users.  5- Program Maintenanc e process of updating software so that it Program maintenance: continues to be useful. A costly process, but can be used to extend the life of a program. Documentation consists of amended program package reflecting what problems occurred and what program changes were made. What Is a Programming Language? A programming language is a set of rules used to write instructions to the computer.