1) BAL (Basic Assembler Language) is a version of IBM's assembler language (sometimes called assembly language) for its System/360 and System/370 mainframe operating system. An assembler language consists of computer instruction to the processor, each specifying a specific processor operation and input or output registers or data areas. Most programs are written in higher-level languages. However, assembler language may be needed for programs that must run using little memory or that must execute very quickly.
2) BAL (branch-and-link) is the name of a System/360/370 assembler language instruction.