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<head><title>Elements of PBASIC Style</title>
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<div class="MCBreadcrumbsBox_0"><span class="MCBreadcrumbsPrefix">You are here: </span><a class="MCBreadcrumbsLink" href="AlphaRef.htm">PBASIC Language Reference</a><span class="MCBreadcrumbsDivider"> &gt; </span><span class="MCBreadcrumbs">Elements of PBASIC Style</span>
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<h1>Elements of PBASIC Style</h1>
<h2>INTRODUCTION</h2>
<p class="PlainText">Like most versions of the BASIC programming language, PBASIC is very forgiving
and the compiler enforces no particular formatting style. As long as the source
code is syntactically correct, it will compile and download to the BASIC Stamp
without trouble.</p>
<p class="PlainText">Why, then, would one suggest a specific style for PBASIC? Consider this: Over
three million BASIC Stamp modules have been sold and there are several thousand
members that participate in the
<a href="http://forums.parallax.com/forums/default.aspx" target="_blank" title="Open Parallax Forums in new window" alt="Open Parallax Forums in new window">Parallax online forums</a>.
This makes it highly likely that you'll be sharing your PBASIC code
with someone, if not co-developing a BASIC Stamp project. Writing code in an
organized, predictable manner will save you -- and your potential colleagues --
a lot of time; in analysis, in troubleshooting and especially when you return to
a project after a long break.</p>
<p class="PlainText">The style guidelines presented here are just that: <i>guidelines</i>. They have
been developed from style guidelines used by professional programmers using other
high-level languages such as Visual Basic<sup>®</sup>, C/C++, and Java™.
Use these guidelines as-is, or modify them to suit your individual needs. The key
is selecting a style the works well for you or your organization, and then
sticking to it.</p>
<h2>PBASIC Style Guidelines</h2>
<h3>1. Do It Right The First Time</h3>
<p class="PlainText">Many programmers, especially new ones, fall into the "<i>I'll knock it out now
and fix it later.</i>" trap. Invariably, the "<i>fix it later</i>" part never
happens and sloppy code makes its way into production projects. If you don't
have time to do it right, when will you find time to do it again?</p>
<p class="PlainText">Start clean and you'll be less likely to introduce errors in your code. And
if errors do pop up, clean and organized formatting will make them easier to find
and fix.</p>
<h3>2. Be Organized and Consistent</h3>
<p class="PlainText">Using a blank program template will help you organize your programs and establish
a consistent presentation.</p>
<h3>3. Use Meaningful Names</h3>
<p class="PlainText">Be verbose when naming constants, variables and program labels. The compiler will
allow names up to 32 characters long. Using meaningful names will reduce the
number of comments and make your programs easier to read, debug and maintain.</p>
<h3>4. Naming I/O Pins</h3>
<p class="PlainText">BASIC Stamp I/O pins are a special case as various elements of the PBASIC language
require a pin to be constant value, an input variable or an output variable. To
prevent redundant definitions, use the PIN type.</p>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
HeaterCtrl PIN 15
</pre>
<p class="PlainText">Since connections don't change during the program run, I/O pins are named like
constants using mixed-case, beginning with an uppercase letter.</p>
<h3>5. Naming Constants</h3>
<p class="PlainText">Begin constant names with an uppercase letter and use mixed case, using uppercase
letters at the beginning of new words within the name.</p>
<img src="../../graphics/bs1_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
SYMBOL AlarmCode = 25
</pre>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
AlarmCode CON 25
</pre>
<h3>6. Naming Variables</h3>
<p class="PlainText">Begin variable names with a lowercase letter and use mixed case, using uppercase
letters at the beginning of new words within the name.</p>
<p class="PlainText">BS1: Avoid using W0 (B0 and B1) so that bit variables (Bit0..Bit15) are
available for use in your programs. Bit variables 0..15 overlay W0, so the use
of W0 may cause undesired effects.</p>
<img src="../../graphics/bs1_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
SYMBOL waterLevel = W1
</pre>
<p class="PlainText">BS2: Avoid the use of internal variable names (such as B0 or W1) in your
programs. Allow the compiler to automatically assign RAM space by declaring a
variable of specific type.</p>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
waterLevel VAR Word
</pre>
<h3>7. Variable Type Declarations</h3>
<p class="PlainText">When using the BS1, variable type is declared by aliasing the SYMBOL name to an
internal variable of a specific size.</p>
<img src="../../graphics/bs1_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
SYMBOL status = Bit0
SYMBOL ovenTmp = B2
SYMBOL rndVal = W2
</pre>
<p class="PlainText">For the BS2, variable types should be in mixed-case and start with an
uppercase letter.</p>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
status VAR Bit
counter VAR Nib
ovenTmp VAR Byte
rndVal VAR Word
</pre>
<p class="PlainText">Conserve BASIC Stamp user RAM by declaring the variable type required to hold
the expected values of the variable. </p>
<img src="../../graphics/bs1_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
SYMBOL bitVal = BIT0 ' 0 - 1
SYMBOL byteVal = B2 ' 0 - 255
SYMBOL wordVal = W2 ' 0 - 65535
</pre>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
bitValue VAR Bit ' 0 - 1
nibValue VAR Nib ' 0 - 15
byteValue VAR Byte ' 0 - 255
wordValue VAR Word ' 0 - 65535 </pre>
<h3>8. Program Labels</h3>
<p class="PlainText">Begin program labels with an uppercase letter, used mixed case, separate words
within the label with an underscore character and begin new words with a number
or uppercase letter. Labels should be preceded by at least one blank line, begin
in column 1 and must be terminated with a colon (except after GOTO and THEN
[in classic PBASIC] where they appear at the end of the line and without a colon).</p>
<img src="../../graphics/bsall_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
Print_String:
READ eeAddr, char
IF char = 0 THEN Print_Done
DEBUG char
eeAddr = eeAddr + 1
GOTO Print_String
Print_Done:
RETURN
</pre>
<h3>9. PBASIC Keywords</h3>
<p class="PlainText">All PBASIC language keywords, including SYMBOL, CON, VAR, PIN and serial/debugging
format modifiers (DEC, HEX, BIN) and constants (CR, LF) should be uppercase. (Although PBASIC
is not case-sensitive, the BASIC Stamp Editor's Syntax Highlighting feature will automatically make
these keywords all caps</p>
<img src="../../graphics/bsall_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
Main:
DEBUG "BASIC Stamp", CR
END
</pre>
<h3>10. Indent Nested Code</h3>
<p class="PlainText">Nesting blocks of code improves readability and helps reduce the introduction of
errors. Indenting each level with two spaces is recommended to make the code
readable without taking up too much space.</p>
<p class="PlainText"><b>Note:</b> <![CDATA[ ]]><i>The dots are used to illustrate the level of nesting and are
<b>not</b> a part of the code.</i></p>
<img src="../../graphics/bs1_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
Main:
..FOR testLoop = 1 TO 10
....IF checkLevel &gt;= Threshold THEN LED_Okay
....lowLevel = lowLevel + 1
....GOTO Loop_Delay
LED_Okay:
....LEDokay = IsOn
Loop_Delay:
....PAUSE 100
..NEXT
..IF testMode = Yes THEN Main
</pre>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
Main:
..DO
....FOR testLoop = 1 TO 10
......IF (checkLevel &lt; Threshold) THEN
........lowLevel = lowLevel + 1
......ELSE
........LEDokay = IsOn
......ENDIF
......PAUSE 100
....NEXT
..LOOP WHILE (testMode = Yes)
</pre>
<h3>11. Condition Statements</h3>
<p class="PlainText">Enclose condition statements in parentheses for clarity (BS2 only - parenthesis
are not allowed when using the BS1).</p>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
Check_Temp:
IF (indoorTemp &gt;= setPoint) THEN
AcCtrl = IsOn
ELSE
lowLevel = lowLevel + 1
ENDIF
</pre><pre class="BScode" xml:space="preserve">
Fill_Water_Tank:
DO WHILE (waterLevel = IsLow)
TankFill = IsOn
PAUSE 250
LOOP
</pre><pre class="BScode" xml:space="preserve">
Get_Delay:
DO
DEBUG HOME, "Enter time (5 - 30)... ", CLREOL
DEBUGIN DEC2 tmDelay
LOOP UNTIL ((tmDelay &gt;= 5) AND (tmDelay =&lt; 30))
</pre>
<h3>12. Be Generous With White Space</h3>
<p class="PlainText">White space (spaces and blank lines) does not affect compiler performance or BASIC
Stamp execution speed, so be generous with it to make listings easier to read. Allow at least one blank line before program labels (two blanks
lines before a subroutine label is recommended). Separate items in a parameter list
with a space.</p>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" /><pre class="BScode" xml:space="preserve">
Main:
DO
ON task GOSUB Update_Motors, Scan_IR, Close_Gripper
LOOP
Update_Motors:
PULSOUT MtrLeft, leftSpeed
PULSOUT MtrRight, rightSpeed
PAUSE 20
task = (task + 1) // NumTasks
RETURN
</pre>
<img src="../../graphics/bs2all_inline.gif" border="0" alt="" />
<p class="PlainText">An exception to this guideline is with the bits parameter used with SHIFTIN
and SHIFTOUT, the REP modifier for DEBUG and SEROUT, and the byte count and
terminating byte value for SERIN. In these cases, format without spaces.</p><pre class="BScode" xml:space="preserve">
SHIFTIN A2Ddata, A2Dclock, MSBPost, [result\9]
</pre><pre class="BScode" xml:space="preserve">
DEBUG REP "*"\25, CR
</pre><pre class="BScode" xml:space="preserve">
SERIN IRbSIO, IRbBaud, [buffer\8\255]
</pre>
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<p style="text-align: right;">Copyright ©&#160;<span class="ContactInfoCompanyName">Parallax Inc.</span></p>
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