COBOL Basics
A D V E R T I S E M E N T
Coding Areas
Syntax
The
Hello World Program
Coding Areas
If you look at the COBOL coding in later sections (e.g.
League Table program in the Sample
code section) the specific positions of coding elements are important for
the compiler to understand. Essentially, the first 6 spaces are ignored by the
compiler and are usually used by the programmer for line numbers. These numbers
arenot the same as those in BASIC where the line number is used as part
of the logic (e.g. GOTO 280, sending the logic to line 280).
The seventh position is called the continuation area.
Only certain characters ever appear here, these being:
* (asterisk), / (solidus or
forward slash), or - (hyphen).
The asterisk is used to precede a comment, i.e. all that
follows is ignored by the compiler. The solidus is used to indicate a page break
when printing coding from the compiler, but it too can be used as comment since
the rest of the line is ignored by the compiler. The hyphen is used as a
continuation marker, i.e. when a quoted literal needs to be extended over to the
next line. It is not for continuing a statement onto the next line (this
is unnecessary*) and also cannot be used to continue a COBOL word. (*You can
write any COBOL statement over as many lines as you like, so long as you stay in
the correct coding region and don't split strings.)
000200*Here is a comment.
000210/A new line for printing and a comment.
000220
:
000340 DISPLAY 'This might be a very long string that
000350- 'needs to be continued onto the next line'
Positions 8 to 11 and 12 to 72 are called area A
and area B, respectively. These are used in specific instances that will
be detailed in later sections.
| Summary |
| Positions |
Designation |
1 to 6
7
8 to 11
12 to 72
|
line code
continuation area
area A
area B
|
Syntax
Identifier names
User-defined names must conform to the following rules:
- Must only consist of alphabetic and numeric characters and/or hyphens
- The name must contain at least one alphabetic character
- Must be no more than 30 characters
- When using hyphens, they must not appear at the beginning or end of the
name
Some examples of legal names:
A123
RecordCount-1
WAGE-IN
Tot-2-out
Like all COBOL code, the compiler will not distinguish
between upper and lower case letters (except within quotes).
Lastly, COBOL has a large list of
reserved words that cannot be
used as identifier names. A list of COBOL reserved words is given elsewhere.
Punctuation
The full stop (period) is the most important punctuation
mark used, and its use will be detailed later (see
Scope terminators).
Generally, every line of the IDENTIFICATION, ENVIRONMENT, and DATA DIVISION end
in a period.
Quotation marks, either single or double, are used to
surround quoted literals (and when calling a sub-program). However, don�t mix
them when surrounding the literal, e.g.
" This is bad �
" but this is ok "
Commas and semi-colons are also used to separate lists of
identifiers, e.g.
MOVE 2 TO DATA-ITEM-1, DATA-ITEM-2, DATA-ITEM-3
A space must follow the comma/semi-colon. They are optional however, and a space
would suffice, but it does add to clarity.
Spelling
Since COBOL was developed in the USA, the spelling of
words is American, e.g. INITIALIZE or ORGANIZATION (using Z rather than S).
Brits be warned!
In many cases, abbreviations and alternative spellings are
available (see reserved word list), e.g. ZERO ZEROS ZEROES all mean the same
thing. Likewise, LINE and LINES, PICTURE and PIC, THROUGH and THRU.
The 'Hello World' Program
As is traditional for all introductory lessons for a
programming language, here's a 'Hello World' program:
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