Direct mode programming allows real-time execution of program parameters without the need for modification and recompilation. It was used in early computing, including BASIC language for beginners. Direct mode programming has evolved into interpreted programming languages and is used in model railroad systems.
Direct mode is a form of computer programming in which program parameters are entered and executed in real time. This is in contrast to a compiled program, which is written to a file, run through a compiler, and then run afterwards. The direct method allows a programmer to test program functionality or perform other immediate tasks or actions on a system without having to modify, recompile, and then run the program again.
Most of the direct mode programming methods were used during the early days of computing. Early punch cards could be seen as such a method, where the programmer programmed the computer via a card and watched the lights on the computer that indicated how the program worked. One of the first typed programming languages is the general purpose symbolic instruction code (BASIC) language for beginners developed in 1964. Many early eight-bit computer systems, such as the Commodore 64®, allowed input of BASIC programs directly when starting the machine. The first thing a user would see is an introduction and a flashing prompt that was waiting for programming commands.
On these systems, a user could then begin programming the computer directly. Usually, this direct mode of operation meant creating and testing a newly developed computer program or using several small BASIC operations to access and start several programs that may have already been saved as files on a floppy disk. In both cases, the most commonly used direct mode command was the RUN command. With RUN you can run a program typed recently in computer memory or a saved file. Modern operating systems, such as Microsoft® Windows®, still allow the use of a RUN command, via a command prompt, to start certain programs on the system.
Due to the increase in computer speed and processing, direct mode programming has evolved into another form in so-called interpreted programming languages. Here, the programming language works just like the old methods, with the one exception that the language comes with an interpreter. The interpreter is a separate program similar to the old eight-bit BASIC prompt. Once started, it sits and waits for commands to be entered in whatever language it was designed to interpret. This allows various interpreted languages to be developed and run on a single computer system, each potentially offering various advantages for particular uses.
Another use for direct mode programming has found its way into model railroad systems. Digital controllers allow a model railway enthusiast to program a series of actions for the locomotive to take, such as speed up and down, the operation of the lights on the train, and more. These controllers have a direct mode programming function, whereby an operator can influence the function of the train in real time as it is crossing the track.
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