History




In the mid-1950s, when assembly language programming was commonly used to write programs for digital computers, the use of macro instructions was initiated for two main purposes: to reduce the amount of program coding that had to be written by generating several assembly language statements from one macro instruction and to enforce program writing standards, e.g. specifying input/output commands in standard ways. Macro instructions were effectively a middle step between assembly language programming and the high-level programming languages that followed, such as FORTRAN and COBOL. Two of the earliest programming installations to develop "macro languages" for the IBM 705 computer were at Dow Chemical Corp. in Delaware and the Air Material Command, Ballistics Missile Logistics Office in California. A macro instruction written in the format of the target assembly language would be processed by a macro compiler, which was a pre-processor to the assembler, to generate one or more assembly language instructions to be processed next by the assembler program that would translate the assembly language instructions into machine language instructions.

By the late 1950s the macro language was followed by the Macro Assemblers. This was a combination of both where one program served both functions, that of a macro pre-processor and an assembler in the same package.failed verification

In 1959, Douglas E. Eastwood and Douglas McIlroy of Bell Labs introduced conditional and recursive macros into the popular SAP assembler, creating what is known as Macro SAP. McIlroy's 1960 paper was seminal in the area of extending any (including high-level) programming languages through macro processors.

Macro Assemblers allowed assembly language programmers to implement their own macro-language and allowed limited portability of code between two machines running the same CPU but different operating systems, for example, early versions of MSDOS and CPM-86. The macro library would need to be written for each target machine but not the overall assembly language program. Note that more powerful macro assemblers allowed use of conditional assembly constructs in macro instructions that could generate different code on different machines or different operating systems, reducing the need for multiple libraries.citation needed

In the 1980s and early 1990s, desktop PCs were only running at a few MHz and assembly language routines were commonly used to speed up programs written in C, Fortran, Pascal and others. These languages, at the time, used different calling conventions. Macros could be used to interface routines written in assembly language to the front end of applications written in almost any language. Again, the basic assembly language code remained the same, only the macro libraries needed to be written for each target language.citation needed

In modern operating systems such as Unix and its derivatives, operating system access is provided through subroutines, usually provided by dynamic libraries. High-level languages such as C offer comprehensive access to operating system functions, obviating the need for assembler language programs for such functionality.citation needed

Comments

Post a Comment

Popular posts from this blog

46)The Republic of Inhospitality

India Republic Day -- While India celebrates Republic Time and the chests of millions of Indians swell with delight at the thought of our huge diversity and imagined army prowess it is well to be able to reflect on what kind of Republic the actual has become. A republican form of government is not merely one out of which the head of state is not a hereditary monarch; rather the modern republic puts on the idea that sovereignty resides inside people and that the will of the testers as expressed through their particular representatives is supreme. What has however been critical to the idea of the republic everywhere is the notion involving inclusiveness. In this respect the tales that have been coming out of India in recent times tell a tale that is relaxing to the bones a tale which usually leaves behind a stench which no amount of sloganeering about Swachh Bharat or even something more than a symbolic wielding with the broom can eradicate. In the event inclusiveness is the touchst
Read more

Macro (computer science)

Image
A macro (short for "macroinstruction", from Greek combining form μακρο- 'long, large') in computer science is a rule or pattern that specifies how a certain input should be mapped to a replacement output. Applying a macro to an input is macro expansion . The input and output may be a sequence of lexical tokens or characters, or a syntax tree. Character macros are supported in software applications to make it easy to invoke common command sequences. Token and tree macros are supported in some programming languages to enable code reuse or to extend the language, sometimes for domain-specific languages. Macros are used to make a sequence of computing instructions available to the programmer as a single program statement, making the programming task less tedious and less error-prone. (Thus, they are called "macros" because a "big" block of code can be expanded from a "small" sequence of characters.) Macros often allow positional or keyword
Read more

Text-substitution macros

Languages such as C and some assembly languages have rudimentary macro systems, implemented as preprocessors to the compiler or assembler. C preprocessor macros work by simple textual substitution at the token, rather than the character level. However, the macro facilities of more sophisticated assemblers, e.g., IBM High Level Assembler (HLASM) can't be implemented with a preprocessor; the code for assembling instructions and data is interspersed with the code for assembling macro invocations. A classic use of macros is in the computer typesetting system TeX and its derivatives, where most of the functionality is based on macros. MacroML is an experimental system that seeks to reconcile static typing and macro systems. Nemerle has typed syntax macros, and one productive way to think of these syntax macros is as a multi-stage computation. Other examples: m4 is a sophisticated stand-alone macro processor. TRAC Macro Extension TAL, accompanying Template Attribute Language SMX: for
Read more