Information SystemsSystem A collection of pieces working together to achieve a common goalAn information system includes Data, People, Procedure, Hardware/SoftwareSystem Development Life Cycle (SDLC) An organized process (or set of steps) used to develop systems in an orderly fashion
PROGRAM, PROGRAMMING & PROGRAMMER• Program: A set of step-by-step instructions that directs a computer to perform a specific task and to produce the required results.• Programming: Programming is a process of designing/ creating a program.• Programmer: Programmer is a person who writes the program.
Problem Opportunity Identification Analysis Design Development & Documentation Testing & InstallationMaintenance & Evaluation One step is completed before proceeding to the next System Development Life Cycle
The Life Cycle of a ProgramProgramming is the process of translating a task into a series of commands a computer will use to perform that task.Programming involves: Identifying the parts of a task the computer can perform. Describing tasks in a specific and complete manner Translating the tasks into a language that is understood by the computer’s CPU.
Program Development Life Cycle Step • Analyze Problem 1 Step • Design Programs 2 Step • Code Programs 3 Step • Debugging 4 Step • Formalize Solution 5 Step • Maintain Programs 6
Step 1 : Analyze ProblemThe problem statement is: The starting point of programming A description of tasks the program is to accomplish How the program will execute the tasks Created through interaction between the developer and the userThe program statement includes error handling and a testing plan
What is involved in analyzing problem? • Review program specifications package • Meet with systems analyst and users • Identify each program’s input, output, and processing components
Step 2 : Design ProgramDevelop an algorithm: A set of specific, sequential steps that describe what the computer program must do Complex algorithms include decision points: Binary (yes/no) Loop (repeating actions) Visual tools used to track algorithm and decision points include: Flowchart Pseudo Code Top Down design Object Oriented Analysis
Step 3 : CodingCoding is translating an algorithm into a programming languageGenerations of programming languages
What is involved in coding programs? Two Steps Translating Entering solution algorithm programming into a programming language code into language the computer
Step 4 : DebuggingRunning a program to find errors is known as debuggingSample inputs are used to determine runtime (logic) errorsDebugger: Tool that helps programmers locate runtime errors
What is involved in testing programs?Goal is to ensure program runs correctly and is error freeThree types of errors Syntax Logic Run time
Syntax Errors• Refers to an error in the syntax of a sequence of characters or tokens that is intended to be written in a particular programming language.• For compiled languages syntax errors occur strictly at compile- time. A program will not compile until all syntax errors are corrected.• For interpreted languages however syntax errors cannot be detected until runtime and it is not necessarily simple to differentiate a syntax error from a semantic error.• A syntax error may also occur when an invalid equation is entered into a calculator. This can be caused, for instance, by opening brackets without closing them, or less commonly, entering several decimal points in one number.
Logic Errors• A logic error (sometimes called a semantic error) is a bug in a program that causes it to operate incorrectly, but not to terminate abnormally (or crash).• A logic error produces unintended or undesired output or other behaviour, although it may not immediately be recognized as such.• Logic errors occur in both compiled and interpreted languages.• Unlike a program with a syntax error, a program with a logic error is a valid program in the language, though it does not behave as intended.
Run time Errors• A runtime error is a computer error that appears in the form of a message box consisting of a particular code along with its corresponding definitions.• Usually, a user will notice that the computer becomes noticeably slow before a runtime error appears.• After the runtime error message has been displayed and closed, the software that shows this error would normally close or freeze. In some cases, the operating system will reboot.• A wide variety of errors cause these problems. These include: • conflicts between the TSR (Terminate and Stay Resident Program) • currently running applications • software issues • memory problems • and harmful applications such as computer viruses
Step 5 : Formalize SolutionWhat is involved in formalizing solution? Programmer performs two activities: • Reviews program code • Reviews documentation
Step 6 : Maintain ProgramsWhat is involved in maintaining programs? Identify errors Identify enhancements Involves modifying existing programs to improve their functionality
Programming language Set of words, symbols, and codes that enables a programmer to communicate a solution algorithm to the computerProgram Development Tool User-friendly software products designed to assist in the creation of information system solutions