Fixed length

• Every single record is exactly the same size
• You have to know in advance how many characters will be assigned to a field
• ✅ It is easy to determine where to read a record, as you know exactly how many spaces each field takes us
• Lots of whitespaces - wasted storage ❌
• Used for postcode/national insurance number

Variable length

• Only the actual data input is stored - used in both serial and sequential files
• No whitespace ✅
• Can’t go directly to read a record ❌
• Used for address, personal statement etc.