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IBM Basic assembly language and successors
The IBM Basic assembly language and successors is a series of assembly languages and assemblers made for the IBM System/360 mainframe system and its successors through the IBM Z.
The first of these, the Basic Assembly Language (BAL), is an extremely restricted assembly language, introduced in 1964 and used on 360 systems with only 8 KB of main memory, and only a card reader, a card punch, and a printer for input/output, as part of IBM Basic Programming Support (BPS/360). The Basic Assembler for BAL was also available as part of Basic Operating System/360 (BOS/360).
Subsequently, an assembly language appeared for the System/360 that had more powerful features and usability, such as support for macros. This language, and the line of assemblers that implemented it, continued to evolve for the System/370 and the architectures that followed, inheriting and extending its syntax. Some in the computer industry referred to these under the generic term "Basic Assembly Language" or "BAL". Many did not, however, and IBM itself usually referred to them as simply the "System/360 Assembler Language", as the "Assembler" for a given operating system or platform, or similar names. Specific assemblers were known by such names as Assembler E, Assembler F, Assembler H, and so forth. Programmers utilizing this language, and this family of assemblers, also refer to them as ALC (for Assembly Language Coding), or simply "the assembler".
The latest derived language is known as the IBM High-Level Assembler (HLASM).
As it is an assembly language, BAL uses the native instruction set of the IBM mainframe architecture on which it runs, System/360, just as the successors to BAL use the native instruction sets of the IBM mainframe architectures on which they run, including System/360, System/370, System/370-XA, ESA/370, ESA/390, and z/Architecture.
The simplicity of machine instructions means that the source code of a program written in assembler will usually be much longer than an equivalent program in, say, COBOL or Fortran. In the past, the speed of hand-coded assembler programs was often felt to make up for this drawback, but with the advent of optimizing compilers, C for the mainframe, and other advances, assembler has lost much of its appeal. IBM continues to upgrade the assembler, however, and it is still used when the need for speed or very fine control is paramount. However, all of the IBM successors to BAL have included a sophisticated macro facility that allows writing much more compact source code.
Another reason to use assembler is that not all operating system functions can be accessed in high level languages. The application program interfaces of IBM's mainframe operating systems is defined as a set of assembly language "macro" instructions, that typically invoke Supervisor Call (SVC) [e.g., on z/OS] or Diagnose (DIAG) [on, e.g., z/VM] instructions to invoke operating system routines. It is possible to use operating system services from programs written in high-level languages by use of assembler subroutines.
The format of assembler language statements reflects the layout of an 80-column punched card, though successive versions have relaxed most of the restrictions.
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IBM Basic assembly language and successors
The IBM Basic assembly language and successors is a series of assembly languages and assemblers made for the IBM System/360 mainframe system and its successors through the IBM Z.
The first of these, the Basic Assembly Language (BAL), is an extremely restricted assembly language, introduced in 1964 and used on 360 systems with only 8 KB of main memory, and only a card reader, a card punch, and a printer for input/output, as part of IBM Basic Programming Support (BPS/360). The Basic Assembler for BAL was also available as part of Basic Operating System/360 (BOS/360).
Subsequently, an assembly language appeared for the System/360 that had more powerful features and usability, such as support for macros. This language, and the line of assemblers that implemented it, continued to evolve for the System/370 and the architectures that followed, inheriting and extending its syntax. Some in the computer industry referred to these under the generic term "Basic Assembly Language" or "BAL". Many did not, however, and IBM itself usually referred to them as simply the "System/360 Assembler Language", as the "Assembler" for a given operating system or platform, or similar names. Specific assemblers were known by such names as Assembler E, Assembler F, Assembler H, and so forth. Programmers utilizing this language, and this family of assemblers, also refer to them as ALC (for Assembly Language Coding), or simply "the assembler".
The latest derived language is known as the IBM High-Level Assembler (HLASM).
As it is an assembly language, BAL uses the native instruction set of the IBM mainframe architecture on which it runs, System/360, just as the successors to BAL use the native instruction sets of the IBM mainframe architectures on which they run, including System/360, System/370, System/370-XA, ESA/370, ESA/390, and z/Architecture.
The simplicity of machine instructions means that the source code of a program written in assembler will usually be much longer than an equivalent program in, say, COBOL or Fortran. In the past, the speed of hand-coded assembler programs was often felt to make up for this drawback, but with the advent of optimizing compilers, C for the mainframe, and other advances, assembler has lost much of its appeal. IBM continues to upgrade the assembler, however, and it is still used when the need for speed or very fine control is paramount. However, all of the IBM successors to BAL have included a sophisticated macro facility that allows writing much more compact source code.
Another reason to use assembler is that not all operating system functions can be accessed in high level languages. The application program interfaces of IBM's mainframe operating systems is defined as a set of assembly language "macro" instructions, that typically invoke Supervisor Call (SVC) [e.g., on z/OS] or Diagnose (DIAG) [on, e.g., z/VM] instructions to invoke operating system routines. It is possible to use operating system services from programs written in high-level languages by use of assembler subroutines.
The format of assembler language statements reflects the layout of an 80-column punched card, though successive versions have relaxed most of the restrictions.