Difference between revisions of "KTurtle/C3/Common-Errors-in-KTurtle/English"

Welcome to this tutorial on Common Errors in KTurtle.

Learning Objectives

• Syntax errors

• Runtime errors and

• Logical errors

System Requirement

Ubuntu Linux OS version 12.04.

KTurtle version. 0.8.1 beta.

Pre-requisites

If not,

for relevant tutorials, please visit our website.

http://spoken-tutorial.org

Definition of Error

Error is a mistake in a program that produces an incorrect or unexpected result.

Syntax Errors

Compilation fails when a program has syntax errors.

Syntax errors are easy to find and fix.

For Example:

• Unmatched parentheses, square brackets and curly braces.

• Use of variable that has not been declared.

• Missing quotes in strings.

Dash home >>In the Search bar type KTurtle

Click on the KTurtle icon.

Click on Dash home. In the Search bar, type KTurtle.

Click on the KTurtle icon.

$a=ask "enter any number and click Ok"

$a=ask within double quotes "enter any number and click Ok"

#$a=ask "enter any number and click ok"

print $a^3'

spritehide

Pause the tutorial here and type the program your into KTurtle editor

Resume the tutorial after typing the program.

Complier shows the following error,

variable "$a" was used without first being assigned to a value.

Remove the comment

$a=ask "enter a number and click ok"

print $a^3

spritehide

Enter 6 for a value and click OK

Program runs without errors.

Type clear command and Run to clean the canvas.

$radian=(pi/180)*$degree

degree=ask "enter an angle value and click OK"

$radian=(pi/180)*$degree

go 50,50

print "Value in radians is"+ " " +$radian

spritehide

Pause the tutorial and type the program your into KTurtle editor

Resume the tutorial after typing the program.

Complier shows the following error,

you cannot put “=” here

$degree=ask "enter an angle value and click OK"

$radian=(pi/180)*$degree

go 50,50

print "Value in radians is"+ " " +$radian

spritehide

Enter 45 for angle value and click OK

Program runs without errors.

$degree=ask "enter an angle value and click OK

$radian=(pi/180)*$degree

go 50,50

print "Value in radians is"+ " " +$radian

spritehide

Complier shows the following error,

Text string was not properly closed, expected a double quote “ ” to close the string.

$degree=ask "enter an angle value and click OK"

$radian=(pi/180)*$degree

go 50,50

print "Value in radians is"+ " " +$radian

spritehide

I will copy the program from text editor and paste it into Kturtle's Editor

Enter 45 for angle value and click OK.

Program runs without errors.

This way you can find the line at which error has occured, and also correct it.

Runtime errors

It may crash the program when you run it.

Runtime errors are commonly due to wrong input from the user.

Compiler cannnot find these errors.

For example:

• Trying to divide by a variable that contains no value.

• Run a loop without a terminating condition or increment value.

Type clear command and Run to clean the canvas.

This program divides two numbers.

'a' is dividend and 'r' is divisor.

$a=ask "enter a number for 'a' and click Ok"'

$r = ask "enter a number for 'r' and click OK"

$d=$a/$r

print $d

I will copy the program from text editor and paste it into KTurtle's Editor.

Pause the tutorial and type the program into your KTurtle editor

Resume the tutorial after typing the program.

le'ts enter 5 for 'a' and click OK

enter 0 for 'r' and click OK

Here we get a runtime error ,

“you tried to divide by zero”

Enter 5 for number and click OK

enter 2 for 'r' and click OK

Program without errors.

Type clear command and Run to clean the canvas.

For example,

Assigning a value to the wrong variable.

Multiplying two numbers instead of adding.

$x=30

message"In while loop, code inside the loop repeats till boolean

evaluates false"

while $x>20 {

$x=$x+1

fontsize 15

forward 20

print $x }

Pause the tutorial here and type the program into your KTurtle editor

Resume the tutorial after typing the program.

A dialog box pops-up, let's click OK.

Loop goes into an infinite loop.

This is a logical error.

In the “while” condition x is greater than 20,

but the variable x is always greater than 20

So, the loop never terminates.

$x=30

message"In while loop, code inside the loop repeats till boolean evaluates false"

while $x>20 {

'$x=$x-1'

fontsize 15

forward 20

print $x }

A dialog box pop-up let's click OK.

Loop terminates after printing values from 29 to 20.

Let us summarise.

Summary

• Use of variable that has not been declared.

• Missing quotes in strings.

• Runtime errors and

• Logical errors

Assignment

$x=3

$y=3

if $x==$y

print"they are equal"

else {

print "they are not equal"}

reset

$x=ask "enter value for x and click Ok"

$y = ask "enter value for y and click Ok"

$g =sqrt ($x*$y)

print "Geometric mean is ="+

learn sum $x {

{$r=0

for $i= 1 to $x{

return $r}

}

print

Acknowledgement

http://spoken-tutorial.org/What is a Spoken Tutorial It summarises the Spoken Tutorial project If you do not have good bandwidth, you can download and watch it

Slide Number 12

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It is supported by the National Mission on Education through ICT, MHRD, Government of India More information on this Mission is available at this link http://spoken-tutorial.org/NMEICT-Intro ]

This is Madhuri Ganpathi from IIT Bombay signing off. Thank you for joining