Why do books and people normally use 'i' for 'for statement'?

Question

i just wonder why books and people normally use 'i' for 'for statement'.
And j or k for the second and third.

what does 'i' stand for?

Answer 1

I think it's for "index"

Answer 2

iteration, most probably.

Answer 3

Norms, just like 'x' and 'y' or 'a' and 'b' being used in algebra expressions.

Answer 4

a(i,j) is used by convention to iterate a (m x n) matrix (2D array) where i iterates (m:rows), j iterates (n:columns), and k iterates (o:depth, if present).

A 1D array is like a 1-column vector (or just data with an "i"ndex).

Infographic + explanation: https://en.m.wikipedia.org/wiki/Matrix_(mathematics)

... debut into programming, Fortran:

http://softwareengineering.stackexchange.com/a/86911

(also reveals why: x,y,z is for floating point)

Answer 5

Your answer in one word - Convention
Using convention in education allows a uniform expression to be used everywhere so that it can be understood by everyone without a new separate explanation everytime.

Answer 6

The syntax of the "for loop" in most programming languages is:

for(initial; final; iteration){}

If we check well, of the three conditions, the first and last begins with "i" ("I"nitial & "I"teration) and the other still has "i" stressed in it (f"i"nal).
This was the answer I came up with when I a asked myself sometime ago...

^^-^^

Answer 7

It goes back to FORTRAN which didn't require you to declare all variables before using them. Variables starting with I, J, K, L, & N were implicitly defined to be integers. Being lazy and the fact the 'DO' loops index variable was required to be an integer, we always started with I

The first programmers using C and Pascal started with
has FORTRAN as their first language and old habits were carried forward and now it's a convento

Answer 8

They are well established convention😉

Answer 9

It comes ultimately from mathematics:
the summation notation traditionally
uses i for the first index, j for the
second, and so on.

Answer 10

It looks good to use "i" but You can use many others... Thank You

Answer 11

i has typically been used as subscript in quite a bit of math for quite some time

Answer 12

there is no condition. u can u different letters also

Answer 13

it looks like easy to suddenly understand for our mind

Answer 14

because as we know that for loop consist of three parts
1. Initialisation
2. Iteration
3. Inspection
so having three I, s in the loop so mostly I is preferred

Answer 15

i is for integer, or int I guess

Answer 16

because the first programmer wrote it that way, and all the programmers ever after were lazy to think about a new name.

Answer 17

Most programmers tend to keep letters a-h for declaring variables,so the next choice is i,j for looping.

Answer 18

consistency. when you have lots of different classes using a universal index of I makes it easy for you and other programmers to understand.

Answer 19

I think there is nothing special with 'i'. It's been used so it is used.You can you any alphabet(unless it is already used)

Answer 20

programming logics are closely related with mathematics... and here the for loop variables are assumed as vectors or metrics thus I,j and k are taken as default notation from these.