Question

Difference between one pass and multipass assembler

Answer 1

Difference between one pass and two pass assembler:
One Pass Assembler
Two Pass Assembler
Scans entire source file only once
Require two passes to scan source file.
First pass – responsible for label definition and introduce them in symbol table.
Second pass – translates the instructions into assembly language or generates machine code.
Generally
• Deals with syntax.
• Constructs symbol table
• Creates label list.
• Indentifies the code segment, data segment, stack segment etc…
Along with pass1 pass two is also required which
• Generates actual Opcode.
• Compute actual address of every label.
• Assign code address for debugging the information.
• Translates operand name to appropriate register or memory code.
• Immediate value is translated to binary strings (1’s and 0’s)
Cannot resolve forward references of data symbols.
Can resolve forward references of data symbols.
No object program is written, hence no loader is required
Loader is required as object code is generated.
Tends to be faster compared to two pass
Two pass assembler requires rescanning. Hence slow compared to one pass assembler.
Only creates tables with all symbols no address of symbols is calculated.
Address of symbols can be calculated

Answer 2

Answer:

The main difference between single pass and multipass compiler is that a single pass compiler is a compiler that passes the source code through each compilation unit only once while a multipass compiler separates compilation into multiple passes, where each pass would continue with the result of the previous pass.