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GET130 Intro to Engineering Technology

Fall 2013


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Programming is FUN!

in addition to being a software package user, engineersand ETs can often benefit from being able to programcomputers for particular tasks solving special / newly discovered problems

simplify your job function / responsibilities promotions!

to do so, we need to learn a programming language rules, reserved words, syntax

MANY computer programming languages / environmentsexist general purpose / special purpose

mathematical/scientific, database/e-commerce, process control,artificial intelligence

BASIC, C, C++, Java, COBOL, Matlab, LabVIEW, PLCs

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BASIC

BeginnersAll-purpose Symbolic Instruction Code

very easy to learn & use carefree formatting, data typing, syntax

created in 1964 at Dartmouth College a family of general-purpose, high-level programming

languages over 300 dialects (http://en.wikipedia.org/wiki/List_of_BASIC_dialects)

has evolved through many incarnations over the years: Tiny-BASIC, Apple BASIC, Micro-Soft BASIC, IBM QuickBASIC,

Microsoft Visual Basic, VB.NET

and now:

Parallax PBASIC, RobotBASIC

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http://en.wikipedia.org/wiki/List_of_BASIC_dialectshttp://en.wikipedia.org/wiki/List_of_BASIC_dialects


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LANGUAGE SUMMARY

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BASIC Programs

BASIC is a line-oriented language

Program= series of statements

StatementStatement

Statement

statements may contain various language elements

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Language Elements

numbers

variables

operators

expressions constants

strings

functions

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covered on the following slides


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Numbers

numeric values for computation, etc

four types in RobotBASIC:: whole numbers

between -2,147,483,648 +2,147,483,647 (32 bit representation)

include a decimal point

2.23E-308 1.79E+308

(32 bit) integers: start with 0%

ex: n=0%110101 // same as n=53

(base 16) integers: start with 0x ex: n=0x1F // same as n=31

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number of unique binary patterns with n bits = 2n


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Variables

are programmer-defined names of storage locations

variable naming rules

must start with a letter, can then have any combination of letters &numbers; are case sensitive

cannot be same as a command, function name, constant name orlabel

RobotBASIC allows variables up to 255 characters

RobotBASIC variables are typeless and do not requiredeclaration before use

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goals = 2 / / goal s i s t he var i abl e name


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Operators

quite similar to calculatoroperators

including precedence rules

RobotBASIC operatorsummary (in precedenceorder) shown to right

note: some operators areRobotBASIC-specific

see Helpfile for examples

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( ) overrides other precedence rules

- unary negation

^ exponentiation

*, / multiply, divide

# modulus (remainder)

% numeric percentage

+, - add, subtract

$ substring test

less, less or equal, greater or equal, greater

=, == equality

, >>,


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Expressions

a formula comprised of numbers, variables, strings,function calls, operators, and other expressions that yieldsa result

used in variable assignments as well as parameters tocommands and function calls

notice precedence rules in that last statement

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I nput "Radi us: ", radiusci r cumf er ence = 2*pi()*radiuspr i nt "Ci r cumf er ence = " , circumferencepr i nt "Ar ea = " , pi() * radius^2

function callnumeric constant

variable referenceoperatorsoperators


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Constants

RobotBASIC provides many predefined names for certainnumeric values

always more meaningful compared to using number

instead of:

also useful in measure conversions:

cc = conversion constant

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Ci r cl e 10, 10, 30, 30, Red

Ci r cl e 10, 10, 30, 30, 4

pr i nt Conver t ( 212, cc_DFtoDC)


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Strings

textual content, arrays of characters

delimited with quotation marks

can apply certain operators to strings

+ performs string concatenation $ performs substring testing

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msg = "al i ve! "Pr i nt "Hel l o Wor l d, "i f " l i ve" $ msg t hen

Pr i nt " I m " + msg + " ! "


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Functions

use to call a built-in or programmer-defined subprogramunit that returns a result

can be used in expressions like pi() in previous example

format:FunctionName(parameter1,parameter2)

parameters separated by commas, may be optional

note use of parentheses; Command statements do not use them

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Pr i nt " l og( 1000) = " , log(1000)


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RobotBASIC Functions

there are MANY functions built in to RobotBASIC

categories: trig, logarithmic, exponential, coordinate, financial

string manipulation

scaling, weight & measure, numberstring

& I/O

, , chrono/calendar, system information

refer to Helpfile for details

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Statement Types

Assignment: assign a value to a variable

Command: built-in features that perform various tasks

Flow Control: control the sequence of program execution

Comment: provides documentation not actually statements

Label: provides a name for a program location

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Comments

Linecomments from // or to end of line

Blockcomments everything between /* and */

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/ / t hi s i s a l i ne comment' so i s t hi s

count = 0 ' i ni t i al i ze count t o 0

/ *************************t hi s i s an exampl eof a bl ock comment

**************************/

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Assignment Statements assigns value to a variable or array element

value can be a constantor result of an expression

formats:Var = expression

Var[] = expression[ ] denotes index to an array variable

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r adi us = 3. 5di amet er = 2*r adi us

Speed[ 5] = 12

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Command Statements

perform built-in tasks input, output, drawing, robot actions, etc.

format:CommandName parameter1,parameter2

commands are not case sensitive

parameters separated by commas, may be optional

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Circle 20, 20, 40, 40, r ed r adi us=10, cent er =30, 30Print "Ci r cl e i s dr awn"End

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Labels

is a marker (think bookmark) for a particular location in the program

use by flow control statements to transfer execution to other than thenext line

includes a colon : where defined

RobotBASIC: can be numeric or alphanumeric style

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I nput "How ol d ar e you? " , agei f age


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Flow Control Statements

control flow of program execution

unconditional

conditional tests & program branching

/ / /

iteration / repetition/

/

//

invoke subroutines / subprograms/

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Conditional: IF evaluates a numeric expression

and conditionally executesstatement(s) based on result

2 formats:IF expressionNTHEN statement

IF expressionNstatement

{ELSEIF expressionN}statement

{ELSE}statement

ENDIF

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a=5If ( a- 3) >0 Then Pr i nt "ok"

' check cof f ee t emper at ur e

t = t empsensor ( )If t >190Pr i nt "t oo hi gh"

ElseIf t


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Iteration: FOR

used when number of loopsneeded is already known

format:

FOR var=expr1NTO expr2N

statement

NEXT

may include optional "STEP"

clause expression2 is generally >

expression1; however, canalso go in decreasing direction

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For i =1 To 5Pr i nt " i =" , I

Next

For i =5 To 20 Step 5Pr i nt iNext

For i =100 To 0 Step - 1Pr i nt i , " bot t l es of beer "

Next' act ual l y, t hi s STEP i s opt i onal

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Iteration: REPEAT

used to repeat a loop until acondition is met

format:

REPEATstatement

UNTIL expressionN

statement(s) execute at leastonce

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Pr i nt "guessi ng game"n=Random( 100)Repeat

I nput "guess?" , g

I f gn

pr i nt "t oo hi gh"El se

pr i nt " that ' s i t ! "

EndI fUntil g=n

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Iteration: WHILE

used to repeat a loop as long asa condition is true

format:

WHILE expressionNstatement

WEND

statement(s) may execute zerotimes!

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' advance r obot car ef ul l y

' get i ni t i al di st anced=sensor_di st ance( )

While d > 5r For war d 5' get new r eadi ngd=sensor _di st ance( )

Wend

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Iteration: Alternative Loop Control

used to handle special circumstances

BREAK:

abandons enclosing loop and continues with statement followingloop

CONTINUE: forces next iteration of enclosing loop

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Subroutines: Gosub-Return

used to organize a codesequence into a module,typically reusable

formats:

GOSUBlabel

GOSUB expressionNstatement

code at labelis executed until aRETURN is reached

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I nput "ent er N: " , nGosub Summat i onPr i nt "summat i on=", t ot alEnd

Summat i on:t ot al =0For i =1 t o n

t ot al = t ot al + iNext

Return

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Subroutines: Call-Return

a more advanced subroutinemechanism that supportsparametersand local variables

parameters are passed by valueor by reference

format:

CALL label{(parameter list)}

code at labelis executed until a

RETURN is reached

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I nput "ent er N: " , nCall Summat i on( n, r esul t )Pr i nt "summat i on=", r esul tEnd

Sub Summat i on( x, &t ot al )t ot al =0For i =1 t o x

t ot al = t ot al + iNext

Return

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ROBOT SIMULATOR

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Robot Simulator

RobotBASIC includes a neat simulated robot environmentwith a collection of associated commands and functions

some features: obstacle detection and abort

robot sensors to detect & avoid obstacles

full color support

robot "tail" that can draw (if "down")

invisible colors are not detected as obstacles

simulated robot battery and charge state heading and position tracking via simulated compass & "GPS"

simulated "slip" factor for motions

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Robot Simulator Commands Summary

creates & locates robot

sets colors that will not be consideredobstacles

defines floor color (default is WHITE) moves forward/backward some number of

pixels

rotates robot CW (+) or CCW (-)

sets robot's heading (0-359 degrees) sets a robot "slowdown" factor

sets robot's pen UP or DOWN

sets a motor slip factor

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Heading Details

and are based on directional compassmeasure as opposed to mathematical angle measures

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0

180

90270

90

270

0180

135

135


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rBumper() details

the robot has 4 bump sensors (switches)

front, rear, left, right

each switch has an assignedbit position in the return value(bottom 4 bits):

each bit is 1 if bump sensor is active (object within 2 pixels) or 0 if not

ex: return value of 4 (01002) means front bumper is active

use bitwise Boolean operators to evaluate result ex:

left front right rear

bit: 3 2 1 0

I f ( rBumper()&4) = 0 t hen ' f r ont bumper i nact i ve

I f ( rBumper()&4) ! = 0 t hen ' f r ont bumper act i ve


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rGround() details

the robot has 3 down-facing sensors

center, 10

each sensor has an assigned sensor number, one of which must bepassed to rGround as an argument 3=10 left, 2=center, 1=10 right

rGround() returns color seen directly under specified sensor and does not ignore any colors, even if invisible

ex: move forward until robot is over something yellow

+10-100

Repeatr For war d 1

Unt i l rGround(2)= YELLOW

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