Editing Line number (section)

===FORTRAN===
In [[Fortran]], as first specified in 1956, line numbers were used to define input/output patterns, to specify statements to be repeated, and for conditional branching. For example:<ref>{{cite book|last1=Programming Research Department, International Business Machines Corporation|title=The FORTRAN Automatic Coding System for the IBM 704 EDPM: Preliminary Operator's Manual|date=April 8, 1957|pages=6–37|url=http://www.softwarepreservation.org/projects/FORTRAN/manual/Prelim_Oper_Man-1957_04_07.pdf}}</ref>

<syntaxhighlight lang="fortran">
   DIMENSION ALPHA(25), RHO(25)
1) FORMAT(5F12.4)
2) READ 1, ALPHA, RHO, ARG
   SUM = 0.0
   DO 3 I=1, 25
   IF (ARG-ALPHA(I)) 4,3,3
3) SUM = SUM + ALPHA(I)
4) VALUE = 3.14159*RHO(I-1)
   PRINT 1, ARG, SUM, VALUE
   GO TO 2
</syntaxhighlight>

Like [[assembler language]] before it, Fortran did not assume every line needed a label (line number, in this case). Only statements referenced elsewhere required a line number:
* Line 1 specifies a format pattern for input; the {{code|READ}} command in line 2 and the later {{code|PRINT}} command both reference this line.
* The {{code|DO}} loop executes line 3.
* The [[arithmetic IF]] statement branches to line 4 on a negative value, line 3 on zero, and again line 3 on a positive value.

While the line numbers are sequential in this example, in the very first "complete but simple [Fortran] program" published the line numbers are in the sequence 1, 5, 30, 10, 20, 2.<ref name="Sayre_1956">{{cite book |title=The FORTRAN Automatic Coding System for the IBM 704 EDPM: Programmer's Reference Manual |publisher=Applied Science Division and Programming Research Department, [[International Business Machines Corporation]] |location=New York, USA |date=1956-10-15 |editor-first=David |editor-last=Sayre |editor-link=David Sayre |author-first1=John Warner |author-last1=Backus |author-link1=John Warner Backus |author-first2=R. J. |author-last2=Beeber |author-first3=Sheldon F. |author-last3=Best |author-first4=Richard |author-last4=Goldberg |author-link4=Richard Goldberg |author-first5=Harlan L. |author-last5=Herrick |author-first6=R. A. |author-last6=Hughes |author-first7=L. B. |author-last7=Mitchell |author-first8=Robert A. |author-last8=Nelson |author-first9=Roy |author-last9=Nutt |author-link9=Roy Nutt |author-first10=David |author-last10=Sayre |author-link10=David Sayre |author-first11=Peter B. |author-last11=Sheridan |author-first12=Harold |author-last12=Stern |author-first13=Irving |author-last13=Ziller |page=46 |url=http://archive.computerhistory.org/resources/text/Fortran/102649787.05.01.acc.pdf |access-date=2022-07-04 |url-status=live |archive-url=https://web.archive.org/web/20220704193549/http://archive.computerhistory.org/resources/text/Fortran/102649787.05.01.acc.pdf |archive-date=2022-07-04}} (2+51+1 pages)</ref>

Line numbers could also be assigned to fixed-point variables (e.g., {{code|ASSIGN}} ''i'' {{code|TO}} ''n'') for referencing in subsequent assigned GO TO statements (e.g., {{code|GO TO}} ''n,(n1,n2,...nm)'').