GET130 Intro to Engineering Technology Fall 2013
2 Programming is FUN! in addition to being a software package user, engineers and ETs can often benefit from being able to program computers 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 / environments exist general purpose / special purpose mathematical/scientific, database/e-commerce, process control, artificial intelligence BASIC, C, C++, Java, COBOL, Matlab, LabVIEW, PLCs
3 BASIC Beginner s All-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
LANGUAGE SUMMARY 4
5 BASIC Programs BASIC is a line-oriented language Program = series of statements Statement Statement Statement statements may contain various language elements
6 Language Elements numbers variables operators expressions constants strings functions covered on the following slides
7 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 number of unique binary patterns with n bits = 2 n
8 Variables are programmer-defined names of storage locations goals = 2 variable naming rules // goals is the variable name 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 or label RobotBASIC allows variables up to 255 characters RobotBASIC variables are typeless and do not require declaration before use
9 Operators quite similar to calculator operators including precedence rules ( ) overrides other precedence rules - unary negation ^ exponentiation *, / multiply, divide # modulus (remainder) % numeric percentage +, - add, subtract RobotBASIC operator summary (in precedence order) shown to right note: some operators are RobotBASIC-specific see Helpfile for examples $ substring test <, <=, >=, > less, less or equal, greater or equal, greater =, == equality <>, ><,!= inequality &&,, @@,! logical AND, OR, XOR, NOT &,, @, ~ bit-wise AND, OR, XOR, NOT >>, << bit shift left, right brotl, brotr bit rotate left, right ++, -- increment once, decrement once +=, -=, *=, /= add / sub / multiply / divide assign
10 Expressions a formula comprised of numbers, variables, strings, function calls, operators, and other expressions that yields a result used in variable assignments as well as parameters to commands and function calls Input "Radius: ", radius circumference = 2*pi()*radius print "Circumference = ", circumference print "Area = ", pi() * radius^2 function call operators numeric constant variable reference notice precedence rules in that last statement
11 Constants RobotBASIC provides many predefined names for certain numeric values always more meaningful compared to using number Circle 10,10,30,30,Red instead of: Circle 10,10,30,30,4 also useful in measure conversions: print Convert(212,cc_DFtoDC) cc = conversion constant
12 Strings textual content, arrays of characters delimited with quotation marks can apply certain operators to strings + performs string concatenation $ performs substring testing msg = "alive!" Print "Hello World," if "live" $ msg then Print "I m " + msg + "!"
13 Functions use to call a built-in or programmer-defined subprogram unit 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 Print "log(1000) = ", log(1000)
14 RobotBASIC Functions there are MANY functions built in to RobotBASIC categories: trig, logarithmic, exponential, coordinate, financial string manipulation scaling, weight & measure, number<->string & I/O,, chrono/calendar, system information refer to Helpfile for details
15 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
16 Comments Line comments from // or to end of line // this is a line comment ' so is this count = 0 'initialize count to 0 Block comments everything between /* and */ /************************* this is an example of a block comment **************************/
17 Assignment Statements assigns value to a variable or array element value can be a constant or result of an expression formats: Var = expression Var[ ] = expression [ ] denotes index to an array variable radius = 3.5 diameter = 2*radius Speed[5] = 12
18 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 Circle 20,20,40,40,red Print "Circle is drawn" End radius=10, center=30,30
19 Labels is a marker (think bookmark ) for a particular location in the program use by flow control statements to transfer execution to other than the next line includes a colon : where defined RobotBASIC: can be numeric or alphanumeric style Input "How old are you? ",age if age<0 then goto Alien Print "you must be human" end Alien: print "you must be alien" end
20 Flow Control Statements control flow of program execution unconditional conditional tests & program branching / / / iteration / repetition / / / / invoke subroutines / subprograms /
21 Conditional: IF evaluates a numeric expression and conditionally executes statement(s) based on result 2 formats : IF expressionn THEN statement IF expressionn statement {ELSEIF expressionn} statement {ELSE} statement ENDIF a=5 If (a-3)>0 Then Print "ok" 'check coffee temperature t = tempsensor() If t>190 Print "too high" ElseIf t<140 Print "too low" Else Print "ok" EndIf { } indicates optional content
22 Iteration: FOR used when number of loops needed is already known format: FOR var=expr1n TO expr2n statement NEXT may include optional "STEP" clause expression2 is generally > expression1; however, can also go in decreasing direction For i=1 To 5 Print "i=",i Next For i=5 To 20 Step 5 Print i Next For i=100 To 0 Step -1 Print i," bottles of beer" Next 'actually, this STEP is optional
23 Iteration: REPEAT used to repeat a loop until a condition is met format: REPEAT statement UNTIL expressionn statement(s) execute at least once Print "guessing game" n=random(100) Repeat Input "guess?",g If g<n print "too low" ElseIf g>n print "too high" Else print "that's it!" EndIf Until g=n
24 Iteration: WHILE used to repeat a loop as long as a condition is true format: WHILE expressionn statement WEND statement(s) may execute zero times! 'advance robot carefully 'get initial distance d=sensor_distance() While d > 5 rforward 5 'get new reading d=sensor_distance() Wend
25 Iteration: Alternative Loop Control used to handle special circumstances BREAK: abandons enclosing loop and continues with statement following loop CONTINUE: forces next iteration of enclosing loop
26 Subroutines: Gosub-Return used to organize a code sequence into a module, typically reusable formats: GOSUB label GOSUB expressionn statement code at label is executed until a RETURN is reached Input "enter N:",n Gosub Summation Print "summation=",total End Summation: total=0 For i=1 to n total = total + i Next Return
27 Subroutines: Call-Return a more advanced subroutine mechanism that supports parameters and local variables parameters are passed by value or by reference format: CALL label{(parameter list)} code at label is executed until a RETURN is reached Input "enter N:",n Call Summation(n,result) Print "summation=",result End Sub Summation(x,&total) total=0 For i=1 to x total = total + i Next Return
ROBOT SIMULATOR 28
29 Robot Simulator RobotBASIC includes a neat simulated robot environment with 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
30 Robot Simulator Commands Summary creates & locates robot sets colors that will not be considered obstacles pixels defines floor color (default is WHITE) moves forward/backward some number of 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
31 Heading Details and are based on directional compass measure as opposed to mathematical angle measures 0º 90º 135º 270º 90º 180º 0º 135º 180º 270º
32 Robot Simulator Functions Summary distance ahead to any obstacle distance to obstacle of particular color obstacle detection using bumper switches obstacle detection using infrared sensors get first color seen directly ahead reads a down-facing sensor looks down for a particular color gets robot's current compass heading gets robot's current X screen position gets robot's current Y screen position
33 rbumper() details the robot has 4 bump sensors (switches) front, rear, left, right each switch has an assigned bit position in the return value (bottom 4 bits): bit: 3 2 1 0 left front right rear each bit is 1 if bump sensor is active (object within 2 pixels) or 0 if not ex: return value of 4 (0100 2 ) means front bumper is active use bitwise Boolean operators to evaluate result ex: If (rbumper()&4) = 0 then 'front bumper inactive If (rbumper()&4)!= 0 then 'front bumper active
34 rfeel() details 0º the robot has 5 infrared sensors center, ±45º, ±90º each sensor has an assigned bit position in the return value (bottom 5 bits): -90º +90º bit: 4 3 2 1 0-90º -45º 0º +45º +90º each bit is 1 if object detected or 0 if not range distance is same as robot's radius ex: return value of 40 (11000 2 ) means objects are towards the left of robot use bitwise Boolean operators to evaluate result as with rbumper()
35 rground() details -10º 0º +10º the robot has 3 down-facing sensors center, ±10º each sensor has an assigned sensor number, one of which must be passed to rground as an argument 3=10º left, 2=center, 1=10º 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 Repeat rforward 1 Until rground(2)= YELLOW