Access

• Three main methods

• Sequential - data can only be viewed in order. To view record 4, we need to read records 1, 2 and 3. Eg magnetic tape, VHS cassette tape

• Indexed sequential - a hash table is provided at the start of the file. To locate record 4, we look in the table and then can go straight to that point. Faster than sequential however requires more storage space than direct, because of the table.

• Direct - data can be viewed in any order. Increased productivity results however more technologically advanced hardware and software is required. Eg DVD, CD, magnetic disk

Storage

• Two main methods

• Online - data is stored to a device that the user has direct and immediate control over ie hard drive, CD Rom, tape, network drive

• Offline - data is stored to a device that the user does not have direct and immediate access to or control over 
• such as any portable storage device that is not available all the time (eg a usb drive may be left at home)
• magnetic tape, optical media (CD or DVD)
• Thumb or USB storage devices.
• used for backup copies of online data 

• Offline storage can result in backup and retrieval issues as well as social and ethical considerations.

• On line storage is being used more often to refer to storage via the internet in an online repository such as dropbox or skydrive (cloud storage)