Why are variables “i” and “j” used for counters?

by

It comes ultimately from mathematics: the summation notation traditionally uses i for the first index, j for the second, and so on. Example (from http://en.wikipedia.org/wiki/Summation):

\sum_{i=1}^{n} i = \frac{n^2 + n}{2}

It’s also used that way for collections of things, like if you have a bunch of variables x1, x2, … xn, then an arbitrary one will be known as xi.

As for why it’s that way, I imagine SLaks is correct and it’s because I is the first letter in Index.

More Related Contents:

  1. Why are variables “i” and “j” used for counters?
  2. How to get variable name?
  3. Creating or referencing variables dynamically in Sass
  4. What’s the difference between placing “mut” before a variable name and after the “:”?
  5. Error if don’t check if {{object.field}} exists
  6. When should an Excel VBA variable be killed or set to Nothing?
  7. Which variable size to use (db, dw, dd) with x86 assembly?
  8. HiveQL: Using query results as variables
  9. Dynamically create variables in PowerShell
  10. In Rust, what’s the difference between “shadowing” and “mutability”?
  11. setq and defvar in Lisp
  12. What is the difference between a member variable and a local variable?
  13. LessCss dynamic variables based on ancestor class
  14. Is it possible to create a multi-line string variable in a Makefile
  15. Powershell pass variable to start-job
  16. How to make points one color when a third column equals zero, and another color otherwise, in Gnuplot?
  17. Batch File Set Variable not working [duplicate]
  18. Determine variable names dynamically according to a string in Fortran
  19. Why there are two ways of declaring variables in Go, what’s the difference and which to use?
  20. Comparing IEEE floats and doubles for equality
  21. Dynamic Variable Naming and Reference (ColdFusion)
  22. Windows Batch files: what is variable expansion, and what does EnableDelayedExpansion mean?
  23. What is the difference between a constant and a static variable and which should I choose?
  24. What is the order of local variables on the stack?
  25. What is “_,” (underscore comma) in a Go declaration?
  26. Declaring global variable with php.ini
  27. Why does Go allow compilation of unused function parameters?
  28. Create a variable in swift with dynamic name
  29. Finding out reason of Pyomo model infeasibility
  30. When should I quote CMake variable references?

Leave a Comment