pass 1 assembler is assembler which convert assembly level language into machine level language in one pass only

Two main options for the design of assembler are:

1. One pass assembler

2. Multi-pass assembler

One pass assemblers generally have problem of "forward referencing" which is resolved by using mulitpasses

One well known and good assembler is NASM. (Netwide ASseMbler). This can be found at http://nasm.sf.net

An assembler which runs on a computer for which it produces object codes