In computing, a line number is a way of specifying a point in a file by enumerating each line in the file by a number. Line numbers are widely used for several purposes. Originally, the word computing was synonymous with counting and calculating, and a computer was a person who computes. ...

In programming, if a programmer introduces a compile-time detectable bug into the program, and attempts to compile it, the compiler will often inform the programmer that the attempt to compile failed at the given line number. This suggests that the line that the compiler reported often contains the error. Computer programming (often simply programming) is the craft of implementing one or more interrelated abstract algorithms using a particular programming language to produce a concrete computer program. ... In computer science, compile time, as opposed to runtime, is the time when a compiler compiles code written in a programming language into an executable form. ... A diagram of the operation of an ideal compiler. ...

In older styles of unstructured programming, line numbers were used to demarcate specific code points where execution was supposed to branch to - in essence, goto commands. For example This page is about the programming command. ...

 10 IF X = 10 GOTO 40 20 X = X + 1 30 GOTO 10 40 PRINT "X is finally 10" 

However, improper use of gotos often led to so-called spaghetti code. Line numbers are now seldom used for this purpose, and even languages which previously allowed branching in this manner now use text labels for program flow control. A plate of spaghetti looks twisted and tangled, which is where the name for spaghetti code comes from. ...