HP 3000 Manuals HP 3000 Manuals
Statements and Their Elements
This section contains the following information:
* Gives the syntax of the general statement and briefly explains each
statement element.
* Explains the different types of statements.
* Provides further information on the statement elements keyword and
identifier.
* Lists the places in a program where spaces are required or are
illegal.
* Compares remarks and comments.
* Explains how statements form a program.
Statement Syntax
Every HP Business BASIC/XL statement has the following syntax, although
not every statement can have all of the optional elements shown. See
"Statement Types" in this chapter for restrictions on the general syntax.
Syntax
{line_num [line_label:]} [Statement_body] [comment]
Parameters
line_num Integer in the range[1, 999999]. Leading zeros are not
significant. Each program line in a program must have a
unique line number. Program lines are executed in line
number order unless control statements specify
otherwise.
line_label Identifier. For a description of an identifier, see
"Identifiers". If a program line has a label, it can be
referenced by either its label or line number.
statement_body The part of the statement that is specified by its
syntax specification. Syntax specifications for
individual statements appear in chapter 4. The
statement-body is composed of the following statement
elements:
Table 3-2. Statement Elements
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| | |
| Statement Element | Explained in |
| | |
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| | |
| Keyword | "Keywords". |
| | |
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| | |
| Variable name | "Variable Names". |
| | |
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| | |
| Spaces | "Spaces". |
| | |
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| | |
| Literal | "Numeric Literals" and "String Literals". |
| | |
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| | |
| Expression | "Operators" or "Subunits". |
| | |
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comment Any character string, including the null string. A
comment cannot follow a HELP command or an IMAGE or DATA
statement.
Statement Types
The HP Business BASIC/XL statement types and their relations are shown in
Figure 3-1. Figure 3-1 also lists the characteristics of each statement
type.
![[]](../../pic3k/M010189/STRUCT3c50.gif)
Figure 3-1. Statement Types
The following are command-only statements:
ANALYST CONTINUE HOP NAME
AUTO COPY INFO REDO
CALLS CWARNINGS LIST RENUMBER
CHANGE EXIT(or ::) LIST SUBS RUN
COMPGO FILES MODIFY STEP
COMPILE FIND MOVE VERIFY
COMPLINK HELP XREF
A command-only statement cannot be a program line. Every other Business
BASIC\XL statement can be a command or a program line. There are also
some statements that cannot be a command. That is, they can only appear
in program lines.
The following are statements that can appear as part of a program line,
but can not be issued as a command:
ACCEPT END WHILE IF THEN ELSE OPEN FORM SUBEND
CASE END IF IMAGE OPTION SUBEXIT
CLEAR FORM ENTER IN DATASET PACKFMT SUBPROGRAM
CLOSE FORM EXIT IF INPUT PAUSE THREAD IS
COPTION EXTERNAL INTEGER READ TINPUT
DATA FLUSH INPUT INTRINSIC READ FORM WHILE
DECIMAL FNEND LENTER REAL WORKFILE IS
DEF FN FOR LINPUT REPEAT WRITE FORM
DIM GLOBAL COPTION LOOP SELECT UNTIL
ELSE GLOBAL EXTERNAL MAT INPUT SHORT DECIMAL
END LOOP GLOBAL INTRINSIC MAT READ SHORT INTEGER
END SELECT GLOBAL OPTION NEXT SHORT REAL
All other statements can be issued as a command, and can appear in a
program line.
Keywords
Keywords are the basis of statements.
A keyword can be entered in the following ways:
* All uppercase letters (for example, PRINT).
* All lowercase letters (for example, print).
A keyword cannot be entered using a combination of uppercase and
lowercase letters; for example, PrINt, or Print.
Regardless of how keywords are entered, HP Business BASIC/XL lists them
in uppercase.
Examples
10 LET B$="Chocolate" !LET is a keyword
20 PRINT X !PRINT is a keyword
30 ON I GOTO 100,200,300 !ON and GOTO are keywords
Identifiers
An identifier is a character string that has the following
characteristics:
* Begins with a letter.
* Contains any combination of letters, digits, and underscores (_).
* Has 63 or fewer characters.
HP Business BASIC/XL uses identifiers for several purposes. Table 3-3
shows those uses.
Table 3-3. Identifier Uses
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| | | |
| Use of Identifier | Required Modifier | Example |
| | | |
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| | | |
| Numeric variable name | None | Total |
| | | |
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| | | |
| Line label | None | Return_point: |
| | | |
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| | | |
| User-defined subprogram name | None | Routine |
| | | |
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| | | |
| User-defined function name | Prefix FN | FNAdd |
| | | |
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| | | |
| String variable name | Suffix $ | Name$ |
| | | |
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An identifier can be entered in the following ways:
* All uppercase letters; for example, NAMES (See note below).
* All lowercase letters; for example, names.
* A combination of uppercase and lowercase letters; for example NaMeS.
NOTE If an identifier has the same spelling as a keyword, it must be
typed in a combination of uppercase and lowercase letters. For
example, "Print" or "pRiNt" is an identifier, but "print" or
"PRINT" is a keyword. If such an identifier appears where the
keyword is illegal, Business BASIC\XL recognizes it as an
identifier. For example, HP Business BASIC/XL interprets "PRINT
IF" as "PRINT If", where If is an identifier.
In general, identifiers should not have the same name and spelling
as keywords. This can be very confusing, especially when
attempting to debug a program.
Regardless of how an identifier is entered, HP Business BASIC/XL prints
it with the first character upshifted and the others downshifted. For
example, "NAMes" and "NAMES" become "Names", and both refer to the same
entity.
Examples
Table 3-4. Legal Identifiers
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| | |
| Legal Identifier | Printed |
| | |
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| | |
| X | X |
| | |
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| | |
| grand_total | Grand_total |
| | |
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| | |
| Sub_total_123 | Sub_total_123 |
| | |
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| | |
| i | I |
| | |
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| | |
| A_ | A_ |
| | |
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| | |
| variablename | Variablename |
| | |
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| | |
| LEGAL_IDENTIFIER | Legal_identifier |
| | |
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Table 3-5. Illegal Identifier
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| | |
| Illegal Identifier | Reason It Is Illegal |
| | |
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| | |
| 1XYZ | First character is not a letter. |
| | |
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| | |
| #illegal | First character is not a letter. |
| | |
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| | |
| sub'total | Contains a character that is not a letter, digit or underscore. |
| | |
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Spaces
One of the following must separate a keyword and an identifier:
* Space.
* Comma.
* Parenthesis.
* Operator.
With few exceptions, spaces can appear anywhere in a program. Table 3-6
lists the places where spaces cannot appear and gives examples.
Table 3-6. Places Where Spaces Are Not Allowed
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| | | |
| Space Is Not Allowed | Correct Example | Incorrect Example |
| | | |
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| | | |
| Within a line number. | 1020 | 10 20 |
| | | |
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| | | |
| Within a keyword. | PRINT | PR INT |
| | | |
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| | | |
| Within an identifier. | Grandtotal | Grand total |
| | | |
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| | | |
| Within a numeric literal. | 10000 | 10 000 |
| | | |
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| | | |
| Within a multicharacter relational operator | <> | < > |
| symbol. | | |
| | | |
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| | | |
| Between the identifier and $ in a string | Astring$ | Astring $ |
| variable name. | | |
| | | |
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| | | |
| Between the FN and the identifier in a | FNAdd | FN Add |
| function name. | | |
| | | |
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When a keyword has an alternate spelling that contains an embedded space,
the two parts can be separated by more than one space. The keywords in
the left column below can also be initially spelled as shown in the right
column. The space in the second column can be replaced with more than
one space. HP Business BASIC/XL prints these keywords as shown in the
left column.
Table 3-7. Keywords with Alternate Spellings
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| | |
| Keyword | Alternate Spelling |
| | |
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| | |
| ENDIF | END IF |
| | |
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| | |
| ENDLOOP | END LOOP |
| | |
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| | |
| ENDSELECT | END SELECT |
| | |
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| | |
| ENDWHILE | END WHILE |
| | |
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| | |
| FNEND | FN END |
| | |
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| | |
| GOSUB | GO SUB |
| | |
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| | |
| GOT0 | GO TO |
| | |
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| | |
| SUBEND | SUB END |
| | |
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| | |
| SUBEXIT | SUB EXIT |
| | |
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Comments versus Remarks
Both comments and remarks are used for documentation only. Table 3-8
summarizes their similarities and differences.
Table 3-8. Comments vs Remarks
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| | | | |
| | Relationship to | How Recognized | Effect on Run-time Efficiency |
| | Program | | |
| | | | |
--------------------------------------------------------------------------------------------------
| | | | |
| Comment | Optional part of | Follows ! on | None (HP Business BASIC/XL ignores |
| | program line. | program line. | everything after !). |
| | | | |
--------------------------------------------------------------------------------------------------
| | | | |
| Remark | Nonexecutable | Begins with the | Slight (HP Business BASIC/XL must |
| | program line. | keyword REM. | read the word REM to determine |
| | | | that it does not need to do |
| | | | anything else for that line). |
| | | | |
--------------------------------------------------------------------------------------------------
A comment can follow an empty statement as shown in line 400:
300 REM This is a remark.
400 !This comment follows an empty statement.
500 PRINT "Hello" !This comment is part of an executable program line.
HP Business BASIC/XL lists a remark with one blank between the keyword
REM and the text of the remark, as in line 300 above. HP Business
BASIC/XL lists a comment with one space before the exclamation point, as
in line 400 above. A comment cannot follow a HELP command.
Program Structure
A program is a sequence of program lines. It is good programming
practice to end a program with an END statement and use STOP statements
within the program if the program must be stopped before it ends.
However, the END statement can appear more than once in a program, and it
need not be the last line.
Syntax
program_line [program_line]...[END] [program_line]...
Parameters
program_line Any statement except a command (that is, any statement
with a line number).
The order that program lines are executed in is determined by line
numbers and control statements. Program lines are executed in line
number order unless control statements specify otherwise. Control
statements are in chapter 4.
The lines of a program can be entered in any order. HP Business BASIC/XL
arranges them in line number order before listing them or executing the
program. Chapter 2 explains how to enter program lines.
A program can be divided into program units, one main program and one or
more subunits. Execution begins with the first line of the main program
unit. Subunits are covered later in this chapter.