Computer machine language

Using the analog and digital devices described above, one can design the on-line communication link, or interface, between the digital computer and the experimental system. Several fundamental considerations must be kept in mind How does the particular computer use, recognize, and interpret information from the outside world How does the computer transmit information What are the computer machine-language instructions available for input/output (I/O) functions ... 

This, it seemed, was what was meant by machine language. A cave dweller could out-talk this apparatus just by grunting, 1 thought. But there was no room for a cynical attitude 1 had only five days to absorb two weeks of computer wisdom. By day three, 1 began to feel the need to seek treatment for a bad case of ones and zeros. Unfortunately, there was no crash cart available for this affliction. 

The ideal programming method is a so-called automatic coding system. In its ultimate form this would require only that the problem be stated in unambiguous mathematical terms. From this statement the computer develops its own efficient machine-language program. While... 

A solution to avoid all the pain of machine-language or assembler is a series of high-level languages, a "compiler," which translates, much as a dictionary would, these instructions into machine code, and a "linker," which connects parts of the task with each other, with "library" routines such as sin(x), cos(x), random(x), and so on, and with input/output (I/O) calls, to create an executable program. The compilers should allow the same "source" code to be compiled, with minor modifications, on any computer "platform" that supports a compiler for that language. 

The computer furnishes the capacity for calculation and controls the operation sequence required by a program. It transfers the data to the central memory. The software transmits the instructions typed on the keyboard and converts them into machine language. 

Step four in the interfacing operation is the use of computer software to communicate with a device and to capture the information it sends for analysis and display. This can be done at a basic level using machine language or higher programming tools such as Visual Basic, but increasingly this capability is provided by manufacturers of instraments, measurement systems, or interface boards. This relieves the user of much of the effort in interfacing devices and allows efficient and easy set up of different experiments typically done in physical chemistry laboratories. As illustration, we consider two examples of measurement approaches that can be used in a number of the experiments in this book. 

Although Occam is very close to being the machine language of the INMOS Transputer, it has not been widely used except on machines based on transputers (e.g., Meiko CS-1, Parsytec, Telmat). In the 1980s, many transputer-based machines were purchased or built by research groups as a (then) very cost-effective source of computer cycles. 

Instruction Set Architecture—the abstract image of a computing system that is seen by a machine language (or assembly language) programmer. This inlcudes the instruction set, memory address modes, processor registers, and address and data formats. 

Most CP/M programs are written in 8080 or Z80 machine language. CP/M takes care of the minor differences between Z80 machines, but you still have to have a Z80 microprocessor. CP/M could be translated to run on any computer, such as the 6502, but what good is a 6502 version of CP/M if all the programs that run under CP/M are written in Z80 machine language ... 

Disk Defaulter" is a short utility, written in machine language, that modifies the computer s operating system to recognize the disk drive as the default device instead of the cassette recorder. As long as the utility is activated, you no longer have to append, 8 to the LOAD, SAVE, and VERIFY commands. 

The machine language for TurboDisk is unusual in that only half of it works within your computer—the rest is actually executed within the 1541 drive itself. Unlike disk drives for most other computers. Commodore s are intelligent units, containing their own microprocessors, RAM, and ROM. This means that they can be programmed for special effects, like Turboloading. 

TurboDisk machine language in the computer reads the incoming data from the serial port s DATA and CLK lines, instead of just the DATA line as in normal serial data transfers. Thus, TurboDisk temporarily converts your serial drive into a two-bit parallel drive. When the entire 256 bytes from a disk sector have been transferred into the computer s buffer, data from the buffer is added to the program in memory while the drive is reading the next sector from the disk. 

In addition, MLX will generate a ready-to-use tape or disk copy of your machine language program. You can then use the LOAD command to read the program into the computer, just like you would with a BASIC program. Specifically, you enter LOAD "filename ,1,1 (for tape) or LOAD "filename",S,l (for disk). 

I hope you will find MLX to be a true labor-saving program. Since it has been tested by entering actual programs, you can count on it as an aid for generating bug-free machine language. Be sure to save MLX it will be used for future applications in other COMPUTE books. 

The following article was originally published in COMPUTEI s Machine Language Routines for tite Commodore 64, copyright 1984, COMPUTE Publications, Inc. "64 Freeze."... 

In the 1950s and 1960s, digital computers became available for calculations in quantum chemistry, but by today s standards, both the computers and the programming languages were extremely primitive. C.C.J. Roothaan devised a computer-adapted matrix form for the Hartree-Fock equations, but his early work with Enrico Clementi on the wave functions of atoms had to be done in a primitive form of machine language. 

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