COP 2121 Basic Cobol Program Structure - Revision history

Jka: /* PARAGRAPHS */

2007-02-23T17:30:21Z

PARAGRAPHS

Jka: /* PROCEDURE DIVISION */

2007-02-23T15:42:15Z

PROCEDURE DIVISION

Jka: /* Data Division */

2007-02-23T15:37:57Z

Data Division

Jka: /* File Section */

2007-02-23T15:30:24Z

File Section

Jka: /* File Section */

2007-02-23T15:14:09Z

File Section

Jka at 20:38, 22 February 2007

2007-02-22T20:38:51Z

New page

==COBOL Program Structure==
* Each COBOL program is divided into four parts, called divisions:
** Identification division
** Environment division
** Data division
** Procedure division
* Division can contain sections
* Sections can contain paragraphs
* Paragraphs contain statements
** A statement or series of statements that end with a period are referred to as a sentence
* Source program line has 80 character positions
* Positions on line reserved for special purposes
** Columns 1-6 and 73-80 optional and rarely used today
** Column 7 for continuation, comment, starting a new page
** Columns 8-72 for COBOL program statements
* Column 7:
** * (asterisk) designates entire line as comment
** / (slash) forces page break when printing source listing
** - (dash) to indicate continuation of nonnumberic literal
* Columns 8-72 divided into two areas
** Area A - columns 8-11
** Area B - columns 12-72
==Margin Rules==
* Division Names
** Examples:
*** IDENTIFICATION DIVISION.
*** ENVIRONMENT DIVISION.
*** DATA DIVISION.
*** PROCEDURE DIVISION.
** Beign in Area A, end with a period
*** First letter of name must begin in column 8-11
*** Entry may extend into Area B
** Must appear on a line with no other entries
* Section Names
** Examples:
*** INPUT-OUTPUT SECTION.
*** FILE SECTION.
*** WORKING-STORAGE SECTION.
** Being in Area A, end with a period
*** First letter of name must begin in column 8-11
*** Entry may extend into Area B
** Must appear on a line with no other entries
* Paragraph-names
** Examples:
*** PROGRAM-ID.
*** MAIN-ROUTINE.
** Being in Area A, end with a period followed by at least one space
** May appear on line by themselves or with other entries. Recommended to be put by themselves for clarity.
* Statements and Sentences
** Examples:
*** SELECT EMPLOYEE-DATA ASSIGN TO "EMP.DAT"
*** COMPUTE WAGES = HOURES*RATE
** Being in Area B (Column 12-72)
** May appear on line by themselves or with other entries
** Statements may end with period but not recommended
** Sentences (e.g. a paragraph made up of one or more statements) end with period followed by at least one space
* Summary
** Division, section and paragraph names begin in Area A
** All other statements begin anywhere in Area B
** Division and section names end with a period
** Paragraph-names and Sentences end with period followed by at least one space
==Identification Division==
* Has no effect on the execution of a program, but is required
* Provides identifying information about program
* Divided into following paragraphs:
** PROGRAM-ID. program-name. (required entry)
** AUTHOR.
** INSTALLATION.
** DATE-WRITTEN.
** DATE-COMPILED.
** SECURITY.
* program-name can be up to eight characters, letters and digits only. Acceptable on all computers.
* PROGRAM-ID starts in Area A
* program-name starts in Area B
==Environment Division==
* Only machine-dependent division
** May change if program is run on a different computer
* Supplies information about the computer equipment to be used in the program
** Describes files and computer devices used to process them
* Optional for COBOL 85, but is required if files are to be processed
===Configuration Section===
* Describes computer used to compile/execute program
* Optional and recommended that you omit it
===Input-Output section===
* Describes input and output files and devices used by program
* Required for all programs using files
==Input-Output Division==
* Follows Configuration section (if coded)
* Included File-control paragraph
** Consists of SELECT statements
** One SELECT statement for each file used by program
** Each SELECT defines a file-name and assigns device name to that file
** Each SELECT statement starts in Area B
===SELECT Statement file-names===
* File-names
** are user-defined words chosen by programmer
** Must follow rules for forming user-defined words
===Rules for User-Defined Words===
# 1 to 30 characters
# Letters, digits, hyphens only
# No embedded blanks
# At least one alphabetic character
# May not begin or end with hyphen
# May not be a COBOL reserved word
===SELECT implementor-names===
* Implementor-name is the path to the file
* Conventions for these names vary widely among computers
===ORGANIZATION clause===
* This clause describes organization of records in the file
* Most disk files created as text files
** Following data for each record, Enter key is pressed
* Use ORGANIZATION IS LINE SEQUENTIAL to
** Correctly read records from files when Enter key is used to mark the end of each record
** Create disk files with each record followed by Enter key so each record appears on separate line when printed
===Coding Guidelines===
# Code SELECT statements in logical order (input files first, then output files) although order is not required
# Use separate lines for SELECT, ASSIGN, ORGANIZATION clauses for readability
# Choose meaningful file-names
* EMPLOYEE-FILE instead of E-FILE
* EMP-REPORT-FILE instead of OUT-FILE
==Data Division==
* Follows Environment Division
* Defines and describes storage for all data
** Files, records, fields in batch programs
** Fields keyed in by the user or displayed on screen to the user in interactive programs
** Any other data fields used by the program
* Each data item is assigned a user-defined name
* Data item names must follow the rules for user-defined name
** Use meaningful data-names that describe contents of field
** Use prefixes or suffixes in data-names when appropriate
===Data Division Sections===
* Two main sections
** File section (required if program uses files)
*** Defines all input and output files and their record formats
** Working-storage section
*** Defines all other fields not part of input or output files but used by the program
* File Section must be described first, followed by the working-storage section
====File Section====
* Each file described with an FD (File Descripor) sentence
* One FD for each SELECT statement in Environment Division
* Format
<pre>
FD file-name
RECORD CONTAINS integer-1 CHARACTERS.
</pre>
** file-name used in FD statement is the same as the file-name used in SELECT statement
** FD is coded in Area A
** RECORD CONTAINS should be coded in Area B
** Period used only at the end of the entire FD
** Recommendation: any clause used in FD appear on a separate line for clarity and ease of debugging

← Older revision		Revision as of 17:30, 23 February 2007
Line 361:		Line 361:
	* A paragraph begins with the paragraph name and ends with the next paragraph or section name or the end of the program text		* A paragraph begins with the paragraph name and ends with the next paragraph or section name or the end of the program text
	* The paragraph name in PROCEDURE DIVISION is a name chosen by the programmer followed by a full stop		* The paragraph name in PROCEDURE DIVISION is a name chosen by the programmer followed by a full stop
		+	* Paragraph-names
		+	** Follow rules for forming data-names except may be all digits: 1010, 1020, etc. are valid paragraph names
		+	** Must be unique
		+	** Coded in Area A, followed by perido
		+	===Sentences and Statements===
		+	* A paragraph is made up of one or more sentences that perform a specific set of operations on the data
		+	* A sentences consists of one or more statements and is terminated by a full stop
		+	<pre>
		+	MOVE .21 to VatRate
		+	COMPUTE VatAmount = ProductCost * VatRate.
		+
		+	DISPLAY "Enter name " WITH NO ADVANCING
		+	ACCEPT StudentName
		+	DISPLAY "Name entered was " StudentName.
		+	</pre>
		+	* A statement consists of a COBOL verb and operand(s)
		+	** SUBTRACT Tax FROM GrossPay GIVING NetPay
		+	** MULTIPLY HOURS BY RATE GIVING WAGES
		+	====Example====
		+	<pre>
		+	IDENTIFICATION DIVISION.
		+	PROGRAM-ID. MultiplyProgram.
		+
		+
		+	DATA DIVISION.
		+	WORKING-STORAGE SECTION.
		+	01 Num1 PIC 9 VALUE ZEROS.
		+	01 Num2 PIC 9 VALUE ZEROS.
		+	01 Result PIC 99 VALUE ZEROS.
		+
		+	PROCEDURE DIVISION.
		+	CalculateResult.
		+	ACCEPT Num1
		+	ACCEPT Num2
		+	MULTIPLY Num1 BY Num2 GIVING Result
		+	DISPLAY "Result is = ", Result
		+	STOP RUN.
		+	</pre>
		+	==[[COP 2121 Some Basic Cobol Verbs]]==

← Older revision		Revision as of 15:42, 23 February 2007
Line 350:		Line 350:

	==PROCEDURE DIVISION==		==PROCEDURE DIVISION==
		+	* Describes the algorithm which will process and produce the data previously described
		+	* Hierarchial in structure and consists of SECTIONS, PARAGRAPHS, SENTENCES, and STATEMENTS
		+	* Only the SECTION is optional. There must be at least one PARAGRAPH, SENTENCE and STATEMENT in the PROCEDURE DIVISION
		+	===SECTION===
		+	* A SECTION is made up of one or more PARAGRAPHS
		+	* A section begins with the SECTION name and ends where the next SECTION name is encountered or where the program text ends
		+	* A section name is the PROCEDURE DIVISION is a name chosen by the programmer followed by the word SECTION followed by a full stop
		+	===PARAGRAPHS===
		+	* Each paragraph is an independent module or routine
		+	* A paragraph begins with the paragraph name and ends with the next paragraph or section name or the end of the program text
		+	* The paragraph name in PROCEDURE DIVISION is a name chosen by the programmer followed by a full stop

← Older revision		Revision as of 15:37, 23 February 2007
Line 348:		Line 348:
	# VALUE clause will be allowed in FILE SECTION		# VALUE clause will be allowed in FILE SECTION
	# Commas and dollar signs will be permissible in numeric literals		# Commas and dollar signs will be permissible in numeric literals
		+
		+	==PROCEDURE DIVISION==

← Older revision		Revision as of 15:30, 23 February 2007
Line 274:		Line 274:
	* Level numbers need not be consecutive; most programmers use increments of 05		* Level numbers need not be consecutive; most programmers use increments of 05
	* By skipping levels, this leaves room for later insertions without having to rewrite the code		* By skipping levels, this leaves room for later insertions without having to rewrite the code
		+	====WORKING-STORAGE Section====
		+	* Follows FILE SECTION
		+	* Starts in Area A, ends with a period
		+	* Defines name, type and size of all other fields (that are not part of input or output files) used by the program
		+	** Example: Data fields for calculations, flags, counters, constants, etc.
		+	* Field names must follow the rules for user-defined names
		+	** For fields not used by program
		+	*** Data-name may be left blank (preferable)
		+	*** May use reserved word FILLER as data-name
		+	*** Size must still be defined using PIC clause
		+	* All fields must be defined at 01 level or in entries subordinate to 01 level entry
		+	* All elementary items (or fields)
		+	** Must include PICTURE clause to define their type and size
		+	** Can be given optional initial valuse with VALUE clauses
		+	=====VALUE clauses=====
		+	* Used to specify an initial value for data fields defined in the WS section
		+	* Example:
		+	<pre>
		+	01 Total PIC 9(5) VALUE initial-value1
		+	01 First-Name PIC X(8) VALUE initial-value2
		+	</pre>
		+	** initial-value1 and initial-value2 are constant (also called literals)
		+	* Constants or literals can be:
		+	** Numeric, 1 to 18 digits
		+	** Non-numeric, 1 to 160 characters
		+	** Figurative: SPACE(S), ZERO(S), QUOTE(S)
		+	======Rules for Numeric Literals======
		+	# 1 to 18 digits
		+	# + or - sign may be included to left of first digit
		+	# Decimal point permitted ''within'' literal. May not follow last digit.
		+	======Rules for Nonnumeric Literals======
		+	* Must be enclosed in quotation marks
		+	* From 1 to 160 characters, including spaces
		+	* Any character in COBOL character set except double quotation mark (")
		+	* May contain all numbers ('125') but not same as numeric literal (125)
		+	** Cannot be used in arithmetic operations
		+	** Cannot be moved to field with PIC of 9's
		+	* Are not data-names
		+	** 'Amount-In' not same as field defined in DATA DIVISION called Amount-In
		+	======Figurative Constants======
		+	* ZERO, ZEROS or ZEROES means all zeros
		+	* SPACE or SPACES means all spaces or blanks
		+	=====VALUE Clause=====
		+	* Literal type must match the field type as defined by PICTURE clause
		+	** ZEROS may be used with both PIC X and PIC 9 fields
		+	** SPAECS may be used only wth alphanumeric fields
		+	** Numeric literals may be used only with PIC 9 fields
		+	** Nonnumeric literals may be used only with PIC X fields
		+	* If omitted, field's value undefined when program begins execution
		+	* May be used only in WORKING-STORAGE SECTION and not in FILE SECTION
		+	* Recommendation: Always initialize the data fields defined in WS section using VALUE clause
		+	=====Continuation of Literals=====
		+	* Nonnumeric literals may be up to 160 characters
		+	* Long literals may not fit on one typed line
		+	* Long literals may be continued from one line to next, although this is not recommended
		+	* Rules for continuation of literals from one line to next
		+	** Begin literal with quotation marks
		+	** Continue literal to position 72. Do not end with quotation mark
		+	** Place hyphen on next line in position 7.
		+	** Continue literal with quotation mark starting anywhere in Area B
		+	** End literal with quotation mark
		+	** Subdividing long literals into seperate fields is recommended
		+	<pre>
		+	01 COLUMN-HDGS.
		+	05 COLUMN-HEADINGS1 PIC X(8) “MONTHLY ”.
		+	05 COLUMN-HEADINGS2 PIC X(12) “TRANSACTIONS”.
		+	05 COLUMN-HEADINGS3 PIC X(10) “ FOR APRIL”.
		+	</pre>
		+	=====COBOL 2008 Changes=====
		+	# Margins A and B rules will be guidelines rather than requirements
		+	# PROGRAM-ID will be only paragraph in IDENTIFICATION DIVISION. All others can be specified as comments
		+	# Length of user-defined words will be increased from 30 to 60 characters
		+	# VALUE clause will be allowed in FILE SECTION
		+	# Commas and dollar signs will be permissible in numeric literals

← Older revision		Revision as of 15:14, 23 February 2007
Line 149:		Line 149:
	** Period used only at the end of the entire FD		** Period used only at the end of the entire FD
	** Recommendation: any clause used in FD appear on a separate line for clarity and ease of debugging		** Recommendation: any clause used in FD appear on a separate line for clarity and ease of debugging
		+	=====RECORD CONTAINS clause=====
		+	* Indicates size of each record
		+	* Optional but recommended since it provides check on record size
		+	* Example
		+	<pre>
		+	FD Sales-File
		+	Record contains 75 characters
		+	</pre>
		+	** If the size of the files in the record definition mistakenly add up to 76 or more, compiler will report a syntax error
		+	=====Defining a Record=====
		+	* Each FD followed by record description entries for the file
		+	* Record description entries specify:
		+	** Name, type and size of the fields to appear in the record
		+	** The order in which the fields appear
		+	** How these fields are related to one another
		+	=====Record Description Entries=====
		+	* Record description entries grouped by levels
		+	** Record-name defined at the 01 level and considered the highest level of data
		+	** Fields within a record defined at subordinate level with numbers from 02 to 49
		+	*** Fields with higher level numbers contain fields with lower level numbers
		+	*** Fields at same level numbers are independent items
		+	=====Record Description Example=====
		+	<pre>
		+	01 Employee-Rec-In.
		+	05 Name-In ...
		+	05 Annual-Salary-In ...
		+	05 Job-Description-In ...
		+	</pre>
		+	* Fields at 05 level subordinate to 01 level entry
		+	* All fields at same level (05) independent or not subordinate to each other
		+	=====Invalid Level Numbers=====
		+	<pre>
		+	01 Employee-Rec-In.
		+	05 Name-In ...
		+	10 First-Name-In
		+	12 Last-Name-In
		+	05 Job-Description-In ...
		+	</pre>
		+	* Last-Name-In level number is invalid since it is not subordinate to First-Name-In
		+	* Both first and last name are at same level and should have same level number
		+	* This is considered a logic error, and would not error at the compilation level
		+	=====Elementary and Group Items=====
		+	* Items defined with a level number are one of two types
		+	** Elementary item - Field that is not further subdivided
		+	*** Must include a PICTURE clause to define its type and size
		+	** Group Item - Field that is further subdivided
		+	*** Has no PICTURE clause
		+	=====PICTURE (PIC) clauses=====
		+	* Specify type and size of the field
		+	* Three types:
		+	** Numeric: only digits (denoted by 9 in PIC clause)
		+	** Alphanumeric: letters, digits, special characters (denoted by X in PIC clause)
		+	** Alphabetic: Only letters and blanks (denoted by A in PIC clause)
		+	* Size:
		+	** Specified by number of digits, either explicitly written out (i.e. XXXX) or abbreviated (i.e. X(4))
		+	* Optional "IS"
		+	<pre>
		+	Cust-ID-In PICTURE IS XXXX
		+	</pre>
		+	* Special characters, 'S', '.', & 'V'
		+	** "PICTURE IS S99V9" for a signed decimal
		+	** V stands for implied decimal, and should be used for all data fileds that will be used in arithmetic operations
		+	** '.' used if the data field is not involved in arithmetic operations and the decimal point needs to be printed
		+	* PICTURE Example
		+	<pre>
		+	01 Employee-Rec-In.
		+	05 Name-In
		+	10 First-Name-In PIC X(8)
		+	10 Last-Name-In PIC X(8)
		+	05 Annual-Salary-In PIC 99999V99
		+
		+	----\|----\|----\|----\|---
		+	Bill Hall 4000000
		+	</pre>
		+	=====Putting it all Together=====
		+	* SELECT defines a file-name for a physical file or device
		+	* FD describes the file
		+	* 01 names the file record
		+	* 02-49 describes fields within the file record
		+	=====Design Example=====
		+	* Problem Specification:
		+	** Given an input file containing a student's course record, output a file containing their GPA record
		+	* Course Record:
		+	** Includes Name, SSN, Courses, Grades
		+	* GPA Record:
		+	** Includes Name, SSN, GPA
		+	<pre>
		+	ENVIRONMENT DIVISION.
		+	INPUT-OUTPUT SECTION.
		+	FILE-CONTROL.
		+	SELECT COURSE-FILE
		+	ASSIGN TO “CourseFile.in“
		+	ORGANIZATION IS LINE SEQUENTIAL.
		+	SELECT GPA-FILE
		+	ASSIGN TO “GPAFile.in“
		+	ORGANIZATION IS LINE SEQUENTIAL.
		+
		+	DATA DIVISION.
		+	FILE SECTION.
		+
		+	FD COURSE-FILE
		+	RECORD CONTAINS 32 CHARACTERS.
		+	01 COURSE-RECORD.
		+	05 FULL-NAME.
		+	10 FIRST-NAME PIC X(10).
		+	10 LAST-NAME PIC X(10).
		+	05 SSN PIC 9(9).
		+	05 COURSE-GRADES.
		+	10 COBOL PIC X.
		+	10 C PIC X.
		+	10 JAVA PIC X.
		+
		+	FD GPA-FILE
		+	RECORD CONTAINS 32 CHARACTERS.
		+	01 GPA-RECORD.
		+	05 NAME PIC x(20).
		+	05 SSN PIC 9(9).
		+	05 GPA PIC 9V99.
		+	</pre>
		+	=====Coding guidelines for Record Description Entries=====
		+	* Record-names are coded in Area A on the 01 level
		+	* All fields are coded on levels 02-49 in Area B
		+	* Subordinate or elementary entries are indented for clarity
		+	* Level numbers need not be consecutive; most programmers use increments of 05
		+	* By skipping levels, this leaves room for later insertions without having to rewrite the code