Editing BASIC-PLUS (section)

==Operation==
Users would sit at a terminal and type in programming language statements. The statements could either be entered into the system's [[command-line interface#Command-line interpreter|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. Using BASIC-PLUS, about half of this virtual address space was used by the combined command interpreter and run-time library (named the [[runtime system|Run Time System]] on RSTS/E). This limited user programs to about 32 [[kilobyte|kB]] of memory.

Large programs were broken into separate executable pieces by use of the {{code|CHAIN}} statement, and programs could [[chain loading|chain]] to specific line numbers in a secondary program to indicate that a program should begin execution at a different point from its first line. This feature of chaining to a certain line number allowed programs to signal to each other that they were being called from another program. The use of a shared memory section called [[core common area|core common]] also allowed programs to pass data to each other as needed. [[Hard disk|Disk]] files could also be used but were slower.

To conserve memory, the system included a garbage collecting memory manager, used for both string data and byte-code.

A running program could be interrupted, have variables examined and modified, and then be resumed.