An Object Laptop is having fields Hard disk, Processor,RAM, and Capacity.
Requirement is to populate field Capacity as 'Low Capacity' when 
Hard disk < 40GB, Processor < 2 GHz and RAM < 1 GB  whenever record is Inserted/Edited. 
I am facing issues when I write trigger for edit case, I am not getting how to compare trigger.oldMap and trigger.newMap here to populate the Capacity field only when it is edited to subsequently meet the criteria. 
Please suggest solution using Trigger Only (as I want to do this by Trigger and not by Workflow Rule or Process Builder). 

Thanks

In salesforce documentation, it is written that enabling bulk api in Data Loader increases capacity of Batch size upto 10,000 but as soon as I enable the Bulk API option, batch size get sets to 2000. Please explain why this is so? 

An Object Laptop is having fields Hard disk, Processor,RAM, and Capacity.
Requirement is to populate field Capacity as 'Low Capacity' when 
Hard disk < 40GB, Processor < 2 GHz and RAM < 1 GB  whenever record is Inserted/Edited. 
I am facing issues when I write trigger for edit case, I am not getting how to compare trigger.oldMap and trigger.newMap here to populate the Capacity field only when it is edited to subsequently meet the criteria. 
Please suggest solution using Trigger Only (as I want to do this by Trigger and not by Workflow Rule or Process Builder). 

Thanks