Interactive vs Batch ProgramsSlide 2Files, Records, FieldsOverview of the Four DivisionsSlide 5Slide 6Sample Interactive ProgramSlide 8Slide 9Data Defined in Sample ProgramPICTURE ClausePICTURE ClausesGiving Field Initial ValuePROCEDURE DIVISIONSlide 15PERFORM … END-PERFORMSlide 17Slide 18Sample Batch ProgramSlide 20COBOL DivisionsDATA DIVISION (will be repeating this many times)Slide 23Slide 24Slide 25100-MAIN-MODULEREAD StatementREAD Statement - 1READ Statement - 2200-WAGE-ROUTINE Entering & Running a ProgramCOMMENTS 1COMMENTS 2COMMENTS 31Interactive vs Batch ProgramsCobol suited for developing both types of programsInteractive programsAccept input data from keyboardInput data processed immediatelyOutput (results) displayed on screen immediately2Interactive vs Batch ProgramsBatch programsProcess large volumes of input at periodic intervalsInput data read in from filesOutput written to filesCan be files on disk, print files, files to be transmitted to a remote location: but files.3Files, Records, FieldsField – a single data item: your name; salary;Record – everything to do with a specific topic, such as all the information about YOU to generate your pay check:Your name, ssan, deductions, address, bank account number, hours worked, overtime hours….File – The grouping of individual records of all employees working in a corporation for whom you want to generate a pay check.Typically read a single record, prepare the output, read next record, and continue until EOF.Book definitions: p. 214Overview of the Four DivisionsEvery COBOL program contains up to four separate divisions in the following order:IDENTIFICATION DIVISIONENVIRONMENT DIVISION DATA DIVISIONPROCEDURE DIVISION5Overview of the Four DivisionsIDENTIFICATION DIVISIONIdentifies program to operating systemProvides documentation about program ENVIRONMENT DIVISIONDefines file-namesDescribes devices used to store themNot included in fully interactive programs6Overview of the Four DivisionsDATA DIVISIONDescribes input and output format of data in filesDefines any constants and work areasPROCEDURE DIVISIONContains instructions to read input, process it and create output7Sample Interactive ProgramPurposeto compute employee WAGESInput from keyboardHOURS and RATEProcessingcompute WAGES as HOURS x RATEOutput displayed on screenWAGES8Sample Interactive ProgramIDENTIFICATION DIVISIONOne required entry, PROGRAM-IDNames the programDATA DIVISIONDescribes and defines storage for all data Data defined in WORKING-STORAGE SECTION for interactive program9IDENTIFICATION DIVISION. PROGRAM-ID. CH0102. DATA DIVISION. WORKING-STORAGE SECTION. 01 SALES-AMOUNT PIC 999V99. 01 SALES-TAX PIC 99.99. Fields; sizes; numeric 01 MORE-DATA PIC XXX VALUE 'YES'. Field; alphanumeric PROCEDURE DIVISION. instructions: operate on data 100-MAIN. PERFORM UNTIL MORE-DATA = 'NO' DISPLAY 'ENTER SALES AMOUNT AS DOLLARS AND CENTS' ACCEPT SALES-AMOUNT reads / accepts from keyboard COMPUTE SALES-TAX = SALES-AMOUNT * .08 DISPLAY SALES-TAX writes to keyboard DISPLAY 'IS THER MORE INPUT (YES OR NO)?‘ prompts user ACCEPT MORE-DATA accepts keyboard input END-PERFORM STOP RUN.Sample COBOL Program – Interactive (no Environment Division)10Data Defined in Sample ProgramKeyed input fields (HOURS, RATE)Output fields (WAGES)Other fields used for processing (MORE-DATA) Wages (not shown)01 WAGES PIC 999.99.11PICTURE Clause01 level begins definition of each fieldmuch more later on this…01 has special significance.PICTURE or PIC clause describesType of dataNumeric (PIC 9)Nonnumeric (PIC X) (alphanumeric)Size of field - determined by number of 9’s or X’s12PICTURE ClausesRATE with PIC 99V99 includes V to show assumed decimal point positionUser enters data with decimal pointProgram uses V to align dataWAGES includes actual decimal point Shown when value displayed on screenWages (not shown)01 WAGES PIC 999.99.13Giving Field Initial ValueMORE-DATA with PIC XXX is nonnumeric fieldAssigned initial contents of YES by use of VALUE clauseValue must be in quotation marks since MORE-DATA is nonnumeric field14PROCEDURE DIVISIONSet of instructions to be executed by programOrganization of instructions planned before coding beginsPseudo-code, an English-like description of program instructions, used for planningDescribes program logic and order in which instructions will be executed15PROCEDURE DIVISIONPROCEDURE DIVISION includes one paragraph 100-MAINNote: program here is horribly simple, as we would expect at this time.There is only one paragraph (module) and a structure chart (architectural design) is almost meaningless – would contain a single box…List of instructions that follow make up paragraphPeriod follows last statement in paragraph (STOP RUN.)Main processing controlled by PERFORM … END-PERFORM loopEND-PERFORM is called a ‘scope terminator.’VERY important!16PERFORM … END-PERFORMRepeats set of instructions as long as user enters YES in response to prompt"IS THERE MORE DATA (YES/NO)?"MORE-DATA initially contains YES so instructions in loop executed first time17PERFORM … END-PERFORMWhen user enters NO as responseMORE-DATA set to "NO" and loop ends After loop, STOP RUN is executed, ending program(Note the indentation of code within the loop. This is essential to good programming style!)18PERFORM … END-PERFORMStatements in loop executed in order they are listedDISPLAY displays value in quotes or value of field on screenACCEPT stores value user enters from keyboard in fieldMULTIPLY performs calculation to find WAGES19Sample Batch ProgramIn batch mode, data comes from input file instead of keyboard Data for each employee stored in a record in file on disk (see page 21)Employee name, hours and rate data called fields20Sample Batch ProgramCalculated results (Wages) stored in file instead of displayed on screen (but can be both displayed as well as stored in a For each input recordRecord created and stored in output fileIncludes employee name, hours, rate and computed wages File intended for printing so spacing added between fields for readabilityI disagree. Most input data is NOT spaced for printing!!!Fields are all contiguous