Assembler

Assembler

An assembler creates object code by translating assembly instruction mnemonics into opcodes, and by resolving symbolic names for memory locations and other entities.The use of symbolic references is a key feature of assemblers, saving tedious calculations and manual address updates after program modifications. Most assemblers also include macro facilities for performing textual substitution—e.g., to generate common short sequences of instructions as inline, instead of called subroutines.

Assemblers have been available since the 1950s and are far simpler to write than compilers for high-level languages as each mnemonic instruction / address mode combination translates directly into a single machine language opcode. Modern assemblers, especially for RISC architectures, such as SPARC or Power Architecture, as well as x86 and x86-64, optimize instruction scheduling to exploit the CPU pipeline efficiently.