INTERPRETER PROJECT APPLICATION

Project: making CODE interpreter using java, the code language specifications are in below

Introduction

CODE is a strongly – typed programming language developed to teach Junior High School students basics of programming. It was developed by a group of students enrolled in the Programming Languages course. CODE is a pure interpreter.

Sample Program:

This is a sample program in CODE

              BEGIN CODE
                INT x, y, z=5
                CHAR a_1=’n’
                BOOL t=”TRUE”
                x=y=4
                a_1=’c’
                # this is a comment
                DISPLAY: x & t & z & $ & a_1 & [#] & “last”
              END CODE
						 
**Output of the sample program:**
	4TRUE5
	n#last

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Language Grammar

Program Structure:
	- all codes are placed inside BEGIN CODE and END CODE
	- all variable declaration is found after BEGIN CODE
	- all variable names are case sensitive and starts with letter or an underscore (_) and followed by a letter, underscore or digits.
	- every line contains a single statement
	- comments starts with sharp sign(#) and it can be placed anywhere in the program
	- executable codes are placed after variable declaration
	- all reserved words are in capital letters and cannot be used as variable names
	- dollar sign($) signifies next line or carriage return
	- ampersand(&) serves as a concatenator
	- the square braces([]) are as escape code
	      
Data Types:
  1. INT – an ordinary number with no decimal part. It occupies 4 bytes in the memory.
  2. CHAR – a single symbol.
  3. BOOL – represents the literals true or false.
  4. FLOAT – a number with decimal part. It occupies 4 bytes in the memory.

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Operators:

 Arithmetic operators
   ( )       - parenthesis
   *, /, %   - multiplication, division, modulo
   +, -      - addition, subtraction
   >, <      - greater than, lesser than
   >=, <=    - greater than or equal to, lesser than or equal to
   ==, <>    - equal, not equal
  
 Logical operators (<BOOL expression><LogicalOperator><BOOL expression>)

   AND       - needs the two BOOL expression to be true to result to true, else false
   OR        - if one of the BOOL expressions evaluates to true, returns true, else false
   NOT       - the reverse value of the BOOL value
   
 Unary operator
  +          - positive
  -          - negative

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Sample Programs

1. A program with arithmetic operation
			BEGIN CODE
				INT xyz, abc=100
				xyz= ((abc *5)/10 + 10) * -1                                                                                      
				DISPLAY: [[] & xyz & []]
			END CODE
Output of the sample program:
[-60]

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3. A program with logical operation
      BEGIN CODE
        INT a=100, b=200, c=300
        BOOL d=”FALSE”
        d = (a < b AND c <>200)
        DISPLAY: d
      END CODE
Output of the sample program:
TRUE

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Code output statement:
      DISPLAY - writes formatted output to the output device
      
Code input statement:
      SCAN – allow the user to input a value to a data type.
      Syntax:
      SCAN: <variableName>[,<variableName>]*
      Sample use:
      SCAN: x, y
      It means in the screen you have to input two values separated by comma(,)
CODE control flow structures:

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1. Conditional

    a. if selection
    	      IF (<BOOL expression>)
    			BEGIN IF
    				 <statement>
    					…
    	       <statement>
    	      END IF
    b. if-else selection
          IF (<BOOL expression>)
          BEGIN IF
              <statement>
            …
              <statement>
          END IF
          ELSE
          BEGIN IF
              <statement>
              …
              <statement>
          END IF
    c. if-else with multiple alternatives
         IF (<BOOL expression>)
         BEGIN IF
               <statement>
               …
               <statement>
         END IF
         ELSE IF (<BOOL expression>)
         BEGIN IF
               <statement>
               …
               <statement>
         END IF
         ELSE
         BEGIN IF
               <statement>
               …
               <statement>
         END IF
   

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2. Loop Control Flow Structures

      a. WHILE (<BOOL expression>)
        BEGIN WHILE
              <statement>
              …
              <statement>
        END WHILE
   

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