What are the functions of passes used in two-pass assembler?
In an assembly language program, two pass translations can handle forward references early.
The subsequent tasks are performed through the passes of a two pass assembler are as given below:
Pass I:
(i) Separate the symbol, operand fields and mnemonic opcode
(ii) Make the symbol table
(iii) Perform the LC processing
(iv) Constructs intermediate representation.
Pass II: Synthesize the objective program
Pass I uses the subsequent data structures:
OPTAB: A table of associated information and mnemonic opcodes
SYMTAB: It is a symbol table
LITTAB: A table literally utilized in the program
OPTAB consists of the field mnemonic opcode, information and class. The class field shows whether the opcode corresponds to a declaration statement (DL) an imperative statement (IS) or an assembler directive (AD).
SYMTAB entry consists of the fields address and length. A LITTAB entry consists of literals and address.