General Format of an instruction

/*
Comments
*/

Label : Opcode operands ; //Comments

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Token	What	Usage
Label	Any Valid Variable name	Used to mark an instruction as well as Data.Instruction may or may not contain Label. Compulsary to mark an instruction when using Branching Operation. ALSO , when declaring a variable Label should clearly be DATA OR when assigning value to a variable , Label must be DATA. SEE : Labels
:	To be used after Label. To be used even if there is no Label	Tells the assembler about end of label. Every Instruction must use : Throws an error otherwise
Opcode	The string representing instruction.	Must be from the list given below. If not , throw an error
Operands	Operands to be used with Opcode.	Must be defined in this procedure , Variable name should be valid , Number of operands must be equal to those demanded by Opcode
;	End of Instruction	Compulsary to use in every instruction. if : is reached directly after ; Or file ends and ; is not present , then throw error.
\\	Single line comments	Everything after ; is ignored as long as it is in same line
/* Comments */	Multi-line comments	Everything in between /* and */ is ignored. Throw error if either of two is missing

Labels

Labels are of two types :

Variable Types	What
ADDRESS	Represents an address. Defined as Label
DATA	Represents Data eg. 2,5,16 etc., Declared explicitly

DATA is a reserved keyword. Whenever defining a variable the label must clearly be DATA.
General Format DATA : type variable name , value ;
Eamples :
>> DATA : int y , 10 ; //variable y declared and assigned value 10
>> DATA : int y ; //variable y declared but not assigned any value.
>> DATA : y = 10 ; //Already assigned vaiable attached a value.

ADDRESS is not a keyword. Any valid variable name can be used to mark address of an instruction
Examples :
>> Addition : Add x ; //Labeled Addition
>> : BRZ Addition ; // No label to it. But can jump to "Address"

VALID VARIABLE NAME :

1. Can contain English alphabets , digits 0-9 and only one special character _.
2. Cannot Start with a digit.
3. Cannot contain tabs , spaces new line etc.

Possible Errors

1)Variable name not valid
2)Variable is already declared

Opcodes

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Opcode	Assembly Opcode	Parameters	Meaning
0000	CLA	-	Clear accumulator
0001	LAC	x	Load into accumulator from address
0010	SAC	x	Store accumulator contents into address
0011	ADD	x	Add address contents to accumulator contents
0100	SUB	x	Subtract address contents from accumulator contents
0101	BRZ	ADDRESS	Branch to address if accumulator contains zero
0110	BRN	ADDRESS	Branch to address if accumulator contains negative value
0111	BRP	ADDRESS	Branch to address if accumulator contains positive value
1000	INP	x	Read from terminal and put in address
1001	DSP	x	Display value in address on terminal
1010	MUL	x	Multiply accumulator contents and address contents
1011	DIV	x , R1 , R2	Divide accumulator contents by **address content **. Quotient in R1 and remainder in R2
1100	STP	-	Stop execution

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Assemble Opcode	Possible Errors
CLA	-
LAC x	Variable not defined , **Variable Type : DATA expected ** , Value not assigned to variable
SAC x	Variable not defined , **Variable Type : DATA expected ** , Value not assigned to variable, Accumulator Contents Not Set
ADD x	Variable not defined , **Variable Type : DATA expected ** , Value not assigned to variable, Accumulator Contents Not Set
SUB x	Variable not defined , **Variable Type : DATA expected ** , Value not assigned to variable, Accumulator Contents Not Set
BRZ ADDRESS	Variable not defined , **Variable Type : ADDRESS expected **
BRN ADDRESS	Variable not defined , **Variable Type : ADDRESS expected **
BRP ADDRESS	Variable not defined , **Variable Type : ADDRESS expected **
INP x	Variable not defined , **Variable Type : DATA expected ** , Value not assigned to variable
DSP x	Variable not defined , **Variable Type : DATA expected ** , Value not assigned to variable
MUL x	Value not defined ,**Variable Type : DATA expected ** , Value not assigned to variable , , Accumulator Contents Not Set
DIV x , R1 , R2	Variable not defined , Zero division error , Variable Type : DATA expected , Value not assigned to variable , Accumulator Contents Not Set
STP	If anything after STP , Not reachable Code

Errors Defined

     
(1) typeMismatchError :          
        (i) `DATA` expected and `ADDRESS` passed and ice-versa.                
        (ii) In `ADD`,`MUL`,`SUB`,`DIV` Type of opperand different from accumulator type.         
        (iii) Variable defied type `A` and found to be type `B`.         
        
(2) variableError :         
        (i) Variable name invalid.     
        (ii) Variable not defined.     
              (a) `ADDRESS` not defined,     
              (b) `DATA` not defined,     
        (iii) Value not assigned.      

(3) syntaxError :     
        (i)`:` missing.      
        (ii) `;` missing.     
        (iii) Opcode invalid.    
        (iv) Possible variable defination , but not labelled `DATA`     
        (v) Multiline comment :   
            (a) Not starting , but ending.     
            (b) Not ending but start found.
            
(4) mathEror :       
    (i)zeroDivisionError

(5) accumulatorContentsNotSetError : Thrown when during program , accumulator is not cleared or No data is loaded. But an operation is done using contents of accumulator.