CS208 Software ProgrammingIntroductionSlide 3LanguagesSlide 5Programming Language Capability RequirementsExample LanguagesProgram DevelopmentProgramsHigh-Level Language ProgrammingTypes of CodeSlide 12Creating Computer ProgramsStructured ProgrammingStructured Programming ConceptsStructured Programming Concepts (continued)Benefits of Structured Programming01/14/19 1CS208 Software Programming2IntroductionSoftwareInstructions that tell the computer what to do (ie. a program)Instructions are written in a programming language3Language LevelsEach type of CPU has its own specific machine languageOther language levels were created to make it easier for a human being to write programsmachine languageassembly languagehigh-level language4LanguagesMachine LanguageZeros and OnesBit representations are specific to a particular hardware architectureAssembly LanguagesUse mnemonics for operations and sometimes also for memory locationsEach assembly language is specific to a particular hardware architectureTranslated by an Assembler5LanguagesHigh Level Languages –Use English-like statements to instruct the computer what to doAre more portable (will run on different kinds of hardware)Are easier for humans to understand and program withTranslated by a Compiler6Programming Language Capability RequirementsRepresentation & Storage (of both the Data and the program Instructions)Data Processing (Interprets the program instructions and carries out the operations defined by these instructions on the Data)Data Input and Data OutputInput Data - data that is provided (is not computed) to the program as it runsOutput Data - data that the program ultimately produces (output data = solution of the computational problem)7Example LanguagesHigh Level LanguagesFORTRAN - scientific/engineering, mathCOBOL - businessBASIC - education and PCsPascal - education C/C++ - application developmentJava - application development8Program DevelopmentProgram development consists of:Discovering the underlying algorithmRepresenting that algorithm as a program using a programming language9ProgramsWhat is a program?A collection of statementsWritten in a programming languageSpecify the steps taken to solve a problemEach programming language has grammar rules that specify:How the statements are formedHow the statements are combined10High-Level Language ProgrammingProgramming requires:A programming language (e.g. C++) to express your ideasA set of tools to edit and debug your codeA compiler to translate your programs to machine code A machine to run the executable code on11Types of CodeSource code (source file)Typed into the editor by the programmer using a programming languageObject Code (object file)Translated from the source code by the compilerExecutable CodeCreated by the linker - links the object code and any necessary library object code files together12Program DevelopmentHigh-Level LanguageProgramDevelopmentComputational ProblemAn Algorithm Source code Program in a High-Level Language (e.g. C++)CompilerA machine LanguageProgram developencodeSourceCodeLinkerObjectCode13Creating Computer ProgramsAnalyze the problemPlan an algorithmHand check the algorithmCode the algorithm (or write program)Hand check (trace through) the programEvaluate and modify program as necessary14Structured ProgrammingStructured Programming is a technique used to create well-formed programsUses top-down design with stepwise refinementLarger pieces of code are broken into shorter pieces of code that encompass a single taskTask are repeatedly broken down into smaller tasks, until they are small enough to be understood easily15Structured Programming ConceptsFinal program is created via top-down design. Main code starts with empty modules, and is slowly refined to lowest level Program is subdivided into modules (one logical task, generally no more than one page long)Keeps programmer from being overwhelmed by the size of the jobAllows easy division of work (modules assigned to different programmers)16Structured Programming Concepts (continued) Each module is organized into recognizable paragraphs, using indentation to show nesting and subordinate clauses.Code structures should have only one entry point and one point of exit (no GOTO).Embedded comments describe the function of each data item and purpose of each module.Straightforward, easily readable code is preferred over slightly more efficient, but obtuse, code.17Benefits of Structured ProgrammingMore readableEasier to maintainMore flexibleMore likely to be correct on first runEasier to "prove" by systematic program