difference between one pass and two pass assembler in tabular form

The difference between one pass and two pass assemblers are:-
A one pass assembler passes over the source file exactly once, in the same pass collecting the labels, resolving future references and doing the actual assembly. The difficult part is to resolve future label references and assemble code in one pass.
A two pass assembler does two passes over the source file ( the second pass can be over a file generated in the first pass ). In the first pass all it does is looks for label definitions and introduces them in the symbol table. In the second pass, after the symbol table is complete, it does the actual assembly by translating the operations and so on.