Charles, the link and chart supplied by Bob below your query does a pretty comprehensive job of illustrating it. It may be a little overwhelming at first, if so, just keep looking and it'll be simple.
Basically (assuming you are playing with the standard reference of your four fretting fingers covering a zone of 4 adjacent frets -although this is sometimes stretched temporarily to 5) whenever you play some segment of a major/minor/modal scale on a guitar or electric bass, you're playing one of 3 things: (1) your 1st, 2cnd, and 4th fingers play (either the 7th, root and 2cnd of the major scale, or the 3rd, 4th, and 5th; or: (2) your 1st, 3rd, and 4th fingers play (either the 6th, 7th, and R of the major scale, or the 2cnd, 3rd, and 4th); or (3) you'll play just 2 notes -the 5th and 6th of the major scale- but which fingers you'll use depends on whether you are playing an instrument tuned in straight 4ths (in which case you'll probably have to skrunch and shift) or not -the inconsistency of the guitar's tuning actually elinates some shifts... on a 6 string bass, all 5 of the caged scales require shifting, but only 3 do on guitar.
Anyway, look closer, and you'll see a simple pattern that applies to ALL 5 of the caged forms:
XYZ... where
X stands for 2 adjacent strings where you finger 124 for both strings, and then go to the next two strings to finger
Y 134 for both strings, and then go to the next STRING (single) and play... (Z) it depends... 1 & 3, or 2& 4, or 1 & 4 skrunch and shift.
This pattern takes 5 strings to complete, and then the next 5 strings have the same exact fingers (except off by one fret). If we had 5 more strings -a 15 string thing- then it would be the same. The pattern just goes on and on. 124 goes to 124 on the next string, then on to 134 on the next string and then 134 again on the next string, and then 13, skrunch and shift, and then repeat!
Anyway, this pattern applies to ALL the caged scales. Once you see it, it's actually pretty simple. If you have any questions, you can email me. I'm not good with computers, I don't know how to get a chart up here, but I could explain it on the phone if you need any help with it!
Take care!