Memory and Storage

Definition: Memory holds data and instructions. It is divided into primary (main) memory and secondary (storage) memory.

Primary Memory

• RAM (Random Access Memory) — temporary, volatile (lost when power is off); holds currently-running programs.
• ROM (Read Only Memory) — permanent, non-volatile; stores start-up instructions.

Secondary Storage

Hard disk, SSD, pen drive, CD/DVD — permanent, larger, slower than RAM.

Units (smallest → largest)

Bit → Byte → KB → MB → GB → TB. 1 Byte = 8 bits; each next unit is ×1024.

Real-world example: Closing a program without saving loses unsaved work because it lived in volatile RAM, not on the disk.

Example 1. Which memory is volatile (erased when power is off)?

• RAM.

Example 2. How many bits are in one byte?

• 8 bits.

Example 3. Arrange from smallest to largest: GB, KB, MB, TB.

• KB < MB < GB < TB.

Quick-revision notes for Memory and Storage — the must-know points for SSC CGL Tier-I/II.

• Memory is primary (RAM, ROM) or secondary (hard disk, SSD, USB).
• RAM (Random Access Memory) is volatile — it loses data when power is off.
• ROM (Read Only Memory) is non-volatile and stores permanent instructions (e.g. BIOS).
• Units: 1 Byte = 8 bits; 1 KB = 1024 B; 1 MB = 1024 KB; 1 GB = 1024 MB; 1 TB = 1024 GB.
• Cache memory is very fast memory between CPU and RAM.
• Secondary storage is non-volatile and used for permanent data (HDD, SSD, DVD).

Cover the answer, recall, then check. 6 cards on the must-know Memory and Storage facts for SSC CGL.

Q1. Which memory is volatile — RAM or ROM?
A1. RAM (it loses data when power is off).

Q2. How many bits are there in one byte?
A2. 8 bits.

Q3. What does 1 GB equal in MB?
A3. 1024 MB.

Q4. What does ROM stand for and is it volatile?
A4. Read Only Memory; it is non-volatile.

Q5. Which memory sits between the CPU and RAM for speed?
A5. Cache memory.

Q6. Give two examples of secondary storage.
A6. Hard disk (HDD) and SSD (also USB/DVD).