Editing Line number (section)

===JOSS===

In 1963, [[JOSS]] independently made line numbers mandatory for every statement in a program and ordered lines in sequential order. JOSS introduced the idea of a single [[command line]] editor that worked both as an interactive language and a program editor. Commands that were typed without a line number were executed immediately, in what JOSS referred to as "direct mode". If the same line was prefixed with a line number, it was instead copied into the program code storage area, which JOSS called "indirect mode".

Unlike FORTRAN before it or BASIC after it, JOSS required line numbers to be fixed-point numbers consisting of a pair of two-digit integers separated by a period (e.g., 1.1). The portion of the line number to the left of the period is known as the "page" or "part", while the portion to the right is known as the "line"; for example, the line number {{code|10.12}} refers to page 10, line 12. Branches can target either a page or a line within a page. When the later format is used, the combined page and line is known as a "step".

Pages are used to define [[subroutine]]s, which return when the next line is on a different page. For instance, if a subroutine for calculating the square root of a number is in page 3, one might have three lines of code 3.1, 3.2 and 3.3, and it would be called using {{code|Do part 3.}} The code would return to the statement after the Do when it reaches the next line on a different page, for instance, 4.1. There is no need for the equivalent of a {{code|RETURN}} at the end, although if an early return is required, {{code|Done}} accomplishes this. Example:
 *Routine to ask the user for a positive value and repeat until it gets one
 01.10 Demand X as "Enter a positive value greater than zero".
 01.20 Done if X>0.
 01.30 To step 1.1