Difference between Random Access Memory (RAM) and Hard Disk Drive (HDD)

A person novice to computers often is in confusion between Random Access Memory (RAM) and Hard Disk Drive (HDD). Here we draw comparisons between the two. Similarities between RAM and HDD : 

• Both are used for storage of data.
• Both are physical components of the computer machine.
• Both RAM and HDD are measured in bytes
• Both RAM and HDD can affect the performance of a computer
• Both RAM and HDD can be upgraded

Differences between RAM and HDD :

S. No.	Parameter	RAM	HDD
1.	Full Form	RAM stands for Random Access Memory.	HDD stands for Hard Disk Drive.
2.	Also known as	RAM is also known as primary memory.	HDD is also known as secondary memory.
3.	Type of storage	The data is temporarily stored in this type of memory.	The data is permanently stored in this type of memory.
4.	Components	RAM does not contains, mechanical parts, only electronical parts like transistors.	HDD contains moving mechanical parts, like the arm.
5.	R/W Time	RAM has shorter R/W time.	HDD has longer R/W time.
6.	Volatile	RAM is a volatile memory. That implies a constant power supply is required for maintaining the contents of the memory.	HDD is a non-volatile memory. That implies a constant power supply is not required for maintaining the contents of the memory cell.
7.	Memory Access	In RAM each and every element takes same time to be accessed.	In HDD different elements take different time to be accessed.
8.	Size	In a system the RAM is smaller than the HDD.	In a system the HDD is larger than the RAM.
9.	Cost	RAM is costlier per unit storage.	HDD is cheaper per unit storage.
10.	Noise	RAM does not produces noise.	HDD can produce noise due to mechanical movements.
11.	Duration of Data	Data stored in RAM is temporary. It remembers as long as it has electricity, i.e. the power is on.	Data stored in HDD is permanent, i.e. it retains data even after shutdown.
12.	Speed of Computer	Inadequate RAM slows down the speed of the computer.	HDD does not affect the speed of the computer.
13.	Form	There are two form factors of RAM- For Desktops and Servers- DIMM (Dual In-line Memory Module) For Laptops- SO-DIMM (Small Outline DIMM)	There are two form factors of HDD- For Desktop Computers- 3.5 inch  For Laptops- 2.5 inch
14.	Usage	To increase the speed of the computer.	To increase the space for storing data or contents of the computer.
15.	Clearing of memory	After running of particular program or application, the memory is cleared.	The memory is not cleared while in use or even after use by an application or program.
16.	Speed	The speed of accessing data is faster than HDD.	The speed of accessing data in HDD is slower as compared to RAM.
17.	Example of existence in different forms	Static RAM (SRAM) Dynamic RAM (DRAM)	Hard disk (magnetic) Floppy disk (magnetic) Tape drive (magnetic) CD-ROM or DVD-ROM (optical)