Pseudocode Web Activity.
The Pseudocode Activity allows small programs to be entered with Pseudocode. It uses an input mechanism which restricts the entry so that only valid code can be entered.
The code can then be run using the Trace Table tab to show how the variable values change as the code is run. There is also the option to run the code line by line
and to show the flow of the program. The Pseudocode is loosely based on the that used by AQA in its Computer Science exams. This activity can be used to give a better understanding of PseudoCode
and as practice for answering the trace table questions in the exam. The activity could be used to help design programs or as a way to start to learn the basic principles of coding.
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Variables Options |
A total of ten variables can be created for use in the PseudoCode. They can be one of six different types and can have a value allocated to them.
Note that if the value is left empty, a default will be allocated. Details on different types of variables can be found further down the help page.
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Set
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The set option relating to a variable allows for a new variable to be created
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Update
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The update option relating to a variable allows the variable name and/or default value to be updated.
If the variable name is changed, any code will be updated to reflect the change.
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Delete
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The delete option relating to a variable allows a variable to be deleted so that a new variable can be created.
If the variable is being used by the code, then an error is displayed and the variable will not be deleted.
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Code Options |
Delete
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The delete options deletes all code assosicated with the current line. The code which is to be removed is firstly highlighted in red with the options to confirm or cancel the action.
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Clear
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The clear option clears the code but does not reset the variables
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Reset
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The reset option clears the code and variables, resetting the state to that when the page is first displayed with a example output "Hello World" command.
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Save
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The save option creates a download of the current variables and code with the name based on the name entered on the "Variables" tab and the .pscode extension.
The code can then be loaded in using the Load opton on the Variable Tab.
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Trace Table Options |
Run
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The run options runs the whole code and displayed each variable update on a separate line
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Output
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The output option runs the whole code and but only displays the output.
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Trace/Step
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The trace option runs the code line by line. Click on the "Step" button for the next line
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Flow/Code
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The flow option toggles between displaying the whole code and displaying the code with line numbers and relevant goto values
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Variable Types |
String
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A string allows for text input. Strings can be compared to text and be assigned to other string variables or text with the option of including any variable value. The default value is the empty string.
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Integers
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An integer allows positive and negative whole numbers to be used. They can be used in comparison statements and have the following
arithmetic operations performed on them: addition (+), subtraction (-), multiplication (x), modulus (MOD - the remainder when integers are divided by each other)
and integer division (DIV). They can also be assigned to the results of the LENGTH, RANDOM, ROUND and FLOOR functions.The default value is 0.
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Float
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A float allows numbers with a fractional part, displayed after the decimal point, to be used. They can be used in comparison statements and have the following
arithmetic operations performed on them: addition (+), subtraction (-), multiplication (x) and division. They can also be assigned to the results of the LENGTH, SQRT, RANDOM, ROUND and FLOOR functions.The default value is 0.
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Count
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A count is used within a FOR statement and can be used as an integer. It is assigned to the firs value in the FOR statement and increased until it exceed the final value.
It can be used within an assignment but it's value cannot be changed. Without a count variable, the FOR statement cannot be used. The default value is 0.
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Boolean
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A boolean can only take the values true and false. It can be used in comparisons statements and have its value updated. It's default value is true.
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Integer Array
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The array represents an array of integers. Either the value can be set to a whole positive number which represents the size. The values will then default to 0s.
Alternative the array can be entered with spaces between each value. If an entry is not an integer, it is set to 0. The default value is "1 2 3", an array of three values.
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String Array
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The array represents an array of strings. The default value is "A B C D E F", an array of six values.
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Commands |
The commands are context specific. Some commands, for example the OUTPUT command, do not require any variables to have been defined before they can be used.
Others are greyed out until they are in the correct state to be used. Additional input is also context specific and variable values, operators and value entry is only presented
at the relevant point when entering a command.
Commands can be removed mid entry by using the delete option, and then re-entered, but it is currently not possible to edit a command.
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LET
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The LET command allows a value, variable or the result of an operation on two of these to be assigned to a variable.
Once this variable value has been entered the LET keyword is removed from the code.
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IF
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The IF command Starts a conditional statement with one or two conditions. For two statements the result is true bepending of the logical operator:
AND requires both statements to be true, OR requires at least one statement to be truef and XOR requires exactly one statement to be true.
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ELSE
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The ELSE command can only be entered before an ENDIF command. It is used for the code which if run when the preceding IF and ELSEIF statements are false.
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ELSEIF
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The ELSEIF command can only be entered before an ELSE or ENDIF command, or before another ELSEIF command. It is used for the code which if run when the preceding IF and ELSEIF statements are false.
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WHILE
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The WHILE command creates a loop which keeps running while the current condition is true. If the condition is immediately false, the code in the loop will never be run.
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REPEAT
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The REPEAT command creates a loop which keeps running while the UNTIL condition is true. The code will always run once before the condition is checked.
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FOR
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The FOR command can only be entered if a count type variable has been created. The count variable is set to the first value. At the end of each loop the count variable is increased by one.
The loop keeps repeating until the the count variable exceeds the last value.
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BREAK
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The BREAK command causes the code to break out of a loop. For this reason, the Break command is only available at the end of a conditional statement within a loop.
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OUTPUT
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The OUTPUT command can take up to two string values each followed by a variable. The contents is displayed in the output column of the trace table
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COMMENT
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The COMMENT command allows text to be entered to explain how the program works. It is ignores within the trace table.
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SHOWALL
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The SHOWALL commands allows all of the variables with the show flag set to be displayed in a row within the trace table.
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BREAKPOINT
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The BREAKPOINT commands caused the code to stop running at that line until the "continue" button is pressed.
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Functions |
Functions can be used in the LET statement. The take a single arugument as a value or variable, and return an integer or a float.
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LENGTH
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Takes an array value and returns the number of items in the array, or takes a string value and returns the length of the string.
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SQRT
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Takes an integer or a float and returns the positive square root of the value.
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RANDOM
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Takes an integer and returns a random integer value between 1 and the given value.
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ROUND
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Takes a float and rounds it to the nearest integer.
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FLOOR
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Takes a float and rounds it down to the highest integer which is equal or less than the given value.
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