What means for i=a,1,-1 in pseudocode?

Question

I have a code in pseudocode.

This is a line of code: for i=k1,1,-1 do Ti <- Ti-1 + Ti.

k1 is an integer. Ti is an array.

The question is: what means for i=k1,1,-1? I know what is for but I don't know what is i=k1,1,-1.

Thank you!

Answer 1

Have i assume values from k1 to 1 with steps of -1. Equivalent to C:

for (i = k1; i >= 1; i += -1)

The syntax in your question is basically same as in Fortran, been around for decades:

      DO 10,i=k1,1,-1
      T(i) = T(i-1) + T(i)
10    CONTINUE