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Basic Assembly Language (BAL) is the commonly used term for a low-level programming language used on IBM System/360 and successor mainframes. Originally "Basic Assembly Language" applied only to an extremely restricted dialect designed to run under control of IBM Basic Programming Support (BPS/360) on systems with only 8 KB of main memory, and only a card reader, a card punch, and a printer for input/output — thus the word "Basic". However, the full name and the initialism "BAL" almost immediately attached themselves in popular use to all assembly-language dialects on the System/360 and its descendants. BAL for BPS/360 was introduced with the System/360 in 1964. Assemblers on other System/360 operating systems through System/370, System/390, and System z, as well as the UNIVAC Series 90 mainframes made by Sperry Corporation, and the BS2000 Mainframes currently made by Fujitsu, inherited and extended its syntax. The latest derived language is known as the IBM High-Level Assembler (HLASM). Programmers utilizing this family of assemblers also refer to them as ALC, (for Assembly Language Coding), or simply "assembler". BAL is also the mnemonic of the "Branch And Link" instruction.〔(【引用サイトリンク】title=HLASM - List of all Opcodes, Extended Mnemonics and Function Codes, Sorted by Mnemonic )〕 ==General characteristics== The architecture of IBM mainframes has undergone several extensions over the years, including System/360, System/370, System/370 XA, ESA/370, ESA/390, and z/Architecture. Each of these architectures has retained compatibility with most of the features of its predecessor. BAL uses the native instruction set of these machines. It is thus closer to the hardware than third-generation languages such as COBOL. The instruction set consists of the low-level operations supported by the hardware, such as: The extreme simplicity of these operations 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. Another reason to use assembler is that not all operating system functions can be accessed in high level languages. The application program interface of mainframe operating systems is defined as a set of assembly language "macro" instructions, that typically invoke Supervisor Call (SVC) (z/OS ) or Diagnose (DIAG) (z/VM ) hardware 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IBM Basic assembly language and successors」の詳細全文を読む スポンサード リンク
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