> j = j - 7 * ( j / 7 )

The expression is a means of returning j in modulus 7 with a language 
which does not have that function. Without checking the original I'd 
guess that it was extracting the day of the week from a number 
representing days.

Recall that integer arithmetic is used.
j/7 gives the integer portion of j/7
7 * (j/7) gives the whole number of 7's in j.
j - 7*(j/7)  gives the number modulus 7

eg if j =  23 = 3 x 7 + 2 the expression gives 2

ie for j = N * 7 + K             ' 0 < K <7 ,  N >= 0
it returns K



        RM

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist