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diff --git a/cobol.html.markdown b/cobol.html.markdown new file mode 100644 index 00000000..1b33f9cc --- /dev/null +++ b/cobol.html.markdown @@ -0,0 +1,198 @@ +--- +language: COBOL +contributors: + - ["Hyphz", "http://github.com/hyphz/"] +filename: learn.COB +--- +COBOL is a business-oriented language revised multiple times since its original design in 1960. It is claimed to still be used in over 80% of +organizations. + +```cobol + *COBOL. Coding like it's 1985. + *Compiles with GnuCOBOL in OpenCobolIDE 4.7.6. + + *COBOL has significant differences between legacy (COBOL-85) + *and modern (COBOL-2002 and COBOL-2014) versions. + *Legacy versions require columns 1-6 to be blank (they are used + *to store the index number of the punched card..) + *A '*' in column 7 means a comment. + *In legacy COBOL, a comment can only be a full line. + *Modern COBOL doesn't require fixed columns and uses *> for + *a comment, which can appear in the middle of a line. + *Legacy COBOL also imposes a limit on maximum line length. + *Keywords have to be in capitals in legacy COBOL, + *but are case insensitive in modern. + *Although modern COBOL allows you to use mixed-case characters + *it is still common to use all caps when writing COBOL code. + *This is what most professional COBOL developers do. + *COBOL statements end with a period. + + *COBOL code is broken up into 4 divisions. + *Those divisions, in order, are: + *IDENTIFICATION DIVISION. + *ENVIRONMENT DIVISION. + *DATA DIVISION. + *PROCEDURE DIVISION. + + *First, we must give our program an ID. + *Identification division can include other values too, + *but they are comments only. Program-id is the only one that is mandatory. + IDENTIFICATION DIVISION. + PROGRAM-ID. LEARN. + AUTHOR. JOHN DOE. + DATE-WRITTEN. 05/02/2020. + + *Let's declare some variables. + *We do this in the WORKING-STORAGE section within the DATA DIVISION. + *Each data item (aka variable) starts with a level number, + *then the name of the item, followed by a picture clause + *describing the type of data that the variable will contain. + *Almost every COBOL programmer will abbreviate PICTURE as PIC. + *A is for alphabetic, X is for alphanumeric, and 9 is for numeric. + + *example: + 01 MYNAME PIC xxxxxxxxxx. *> A 10 character string. + + *But counting all those x's can lead to errors, + *so the above code can, and should + *be re-written as: + 01 MYNAME PIC X(10). + + *Here are some more examples: + 01 AGE PIC 9(3). *> A number up to 3 digits. + 01 LAST_NAME PIC X(10). *> A string up to 10 characters. + + *In COBOL, multiple spaces are the same as a single space, so it is common + *to use multiple spaces to line up your code so that it is easier for other + *coders to read. + 01 inyear picture s9(7). *> S makes number signed. + *> Brackets indicate 7 repeats of 9, + *> ie a 6 digit number (not an array). + + *Now let's write some code. Here is a simple, Hello World program. + IDENTIFICATION DIVISION. + PROGRAM-ID. HELLO. + DATA DIVISION. + WORKING-STORAGE SECTION. + 01 THE-MESSAGE PIC X(20). + PROCEDURE DIVISION. + DISPLAY "STARTING PROGRAM". + MOVE "HELLO WORLD" TO THE-MESSAGE. + DISPLAY THE-MESSAGE. + STOP RUN. + + *The above code will output: + *STARTING PROGRAM + *HELLO WORLD + + + + ********COBOL can perform math*************** + ADD 1 TO AGE GIVING NEW-AGE. + SUBTRACT 1 FROM COUNT. + DIVIDE VAR-1 INTO VAR-2 GIVING VAR-3. + COMPUTE TOTAL-COUNT = COUNT1 PLUS COUNT2. + + + *********PERFORM******************** + *The PERFORM keyword allows you to jump to another specified section of the code, + *and then to return to the next executable + *statement once the specified section of code is completed. + *You must write the full word, PERFORM, you cannot abbreviate it. + + IDENTIFICATION DIVISION. + PROGRAM-ID. HELLOCOBOL. + + PROCEDURE DIVISION. + FIRST-PARA. + DISPLAY 'THIS IS IN FIRST-PARA'. + PERFORM THIRD-PARA THRU FOURTH-PARA. *>skip second-para and perfrom 3rd & 4th + *> then after performing third and fourth, + *> return here and continue the program until STOP RUN. + + SECOND-PARA. + DISPLAY 'THIS IS IN SECOND-PARA'. + STOP RUN. + + THIRD-PARA. + DISPLAY 'THIS IS IN THIRD-PARA'. + + FOURTH-PARA. + DISPLAY 'THIS IS IN FOURTH-PARA'. + + + *When you compile and execute the above program, it produces the following result: + THIS IS IN FIRST-PARA + THIS IS IN THIRD-PARA + THIS IS IN FOURTH-PARA + THIS IS IN SECOND-PARA + + + **********Combining variables together using STRING *********** + + *Now it is time to learn about two related COBOL verbs: string and unstring. + + *The string verb is used to concatenate, or put together, two or more stings. + *Unstring is used, not surprisingly, to separate a + *string into two or more smaller strings. + *It is important that you remember to use ‘delimited by’ when you + *are using string or unstring in your program. + + IDENTIFICATION DIVISION. + PROGRAM-ID. LEARNING. + ENVIRONMENT DIVISION. + DATA DIVISION. + WORKING-STORAGE SECTION. + 01 FULL-NAME PIC X(20). + 01 FIRST-NAME PIC X(13) VALUE "BOB GIBBERISH". + 01 LAST-NAME PIC X(5) VALUE "COBB". + PROCEDURE DIVISION. + STRING FIRST-NAME DELIMITED BY SPACE + " " + LAST-NAME DELIMITED BY SIZE + INTO FULL-NAME + END-STRING. + DISPLAY "THE FULL NAME IS: "FULL-NAME. + STOP RUN. + + + *The above code will output: + THE FULL NAME IS: BOB COBB + + + *Let’s examine it to see why. + + *First, we declared all of our variables, including the one that we are creating + *by the string command, in the DATA DIVISION. + + *The action takes place down in the PROCEDURE DIVISION. + *We start with the STRING keyword and end with END-STRING. In between we + *list what we want to combine together into the larger, master variable. + *Here, we are combining FIRST-NAME, a space, and LAST-NAME. + + *The DELIMITED BY phrase that follows FIRST-NAME and + *LAST-NAME tells the program how much of each variable we want to capture. + *DELIMITED BY SPACE tells the program to start at the beginning, + *and capture the variable until it runs into a space. + *DELIMITED BY SIZE tells the program to capture the full size of the variable. + *Since we have DELIMITED BY SPACE after FIRST-NAME, the GIBBERISH part is ignored. + + *To make this clearer, change line 10 in the above code to: + + STRING FIRST-NAME DELIMITED BY SIZE + + *and then re-run the program. This time the output is: + + THE FULL NAME IS: BOB GIBBERISH COBB + + + + + + +``` + +##Ready For More? + +* [GnuCOBOL](https://sourceforge.net/projects/open-cobol/) + |