40 and 80 cables are essentially the same although 80 cables are for faster devices like hard drives. Both should have 40 "holes" on the cable connectors to connect to IDE headers on your motherboard.
SCSI is very different, usually either 50 pin or 68 pin cables and devices but old 25 pin devices still exist. There are 80 pin devices called SCA connectors, usually hard drives from servers.
50 pin scsi cables have female connectors
68 pin scsi cables have male connectors.
You should have hard disk alone connected on ATA100 80 ribbon cable to IDE 0 on motherboard ("master" jumper setting) and the DVD and CDRW can share the 40 ribbon cable, one set as master and one set as slave on IDE 1.
I hope this makes sense.
Consequently scsi 50 pin devices have "pins" (male) and 68 pin devices have hole (female)
80 pin scis/SCA devices have holes that transfer both data and power.
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