BASIC-PLUS

BASIC-PLUS is an extended dialect of the BASIC programming language that was developed by Digital Equipment Corporation (DEC) for use on its RSTS/E time-sharing operating system for the PDP-11 series of 16-bit minicomputers in the early 1970s through the 1980s. BASIC-PLUS was based on BASIC-8 for the TSS/8, itself based very closely on the original Dartmouth BASIC. BASIC-PLUS added a number of new structures, as well as features from JOSS concerning conditional statements and formatting. In turn, BASIC-PLUS was the version on which the original Microsoft BASIC was patterned. Notable among the additions made to BASIC-PLUS was the introduction of string functions like and , in addition to Dartmouth's original all-purpose command. In future versions of the language, notably Microsoft's, was removed and BASIC-PLUS's string functions became the only ways to perform these sorts of operations. Most BASICs to this day follow this convention. The language was later rewritten as a true compiler as BASIC-Plus-2, and was ported to the VAX-11 platform as that machine's native BASIC implementation. This version survived several platform changes, and is today known as VSI BASIC for OpenVMS. Users would sit at a terminal and type in programming language statements. The statements could either be entered into the system's command interpreter directly, or entered into a text editor, saved to a file, and loaded into the command interpreter from the file. Errors in source code were reported to the user immediately after the line was typed. As a smart terminal with cursor control could not be guaranteed, BASIC-PLUS used the common system of prefixing all source code with a line number. The code was edited by typing in the number and then changing the contents of the following code. A line of code could be removed by typing in its line number and nothing else, thereby setting it to an empty line. The virtual address space of an RSTS/E user was limited to a little less than 64KB of space.