Memory

Memory Unit

Used to represent the data size. A bit is the smallest unit size. The data is stored in binary value of 0 or 1. Computer memory is stored into smaller parts called as cells which has unique address in between 0 and it's size - 1.

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Types of memory

Based on location, it is of 4 types.

1. Register memory
2. Cache memory
3. Primary memory
   1. RAM - Volatile
      1. DRAM - dynamic
      2. SRAM - static
   2. ROM - Nonvolatile
      1. PROM
      2. EPROM
      3. EEPROM
4. Secondary memory
   1. Fixed storage
      1. HDD - Hard Disk Drive
      2. SSD - Solid State Disk
      3. Internal flash memory
   2. Removable storage
      1. Optical disks
      2. Memory cards
      3. Pendrives
      4. Floppy disks
      5. Magnetic tapes

1. Register memory

• Smallest and fastest memory in computer.
• It is in the form of registers reside inside CPU.
• Temporarily stores the data for faster access by CPU.

2. Cache memory

• Small and faster than primary memory.
• It stores the frequently used data or instructions by CPU.

3. Primary memory

• It is the part of the computer unlike secondary memory.

3.A. RAM (Random Access Memory)

• It is volatile memory means that it stores data or instructions temporarily.
• It loses all data when we shut down the computer.
• It system's RAM is more, it works faster.

3.A.I. DRAM (Dynamic RAM)

• It refreshes it's memory constantly.

3.A.II. SRAM (Static RAM)

• It doesn't need to refresh so much constantly unlike DRAM.
• As it acts like system cache it works faster than DRAM.

3.B. ROM (Read Only Memory)

• It is nonvolatile memory means that it stores data or instructions permanently.
• It doesn't loose data when we shut down and helps in getting instructions for booting process.

3.B.I. PROM (Programmable ROM)

• Once program is written in PROM, it remains there forever.

3.B.II. EPROM (Erasable Programmable ROM)

• Until the memory is exposed to ultraviolet light, the content will be there forever.

3.B.III. EEPROM (Electrically Erasable Programmable ROM)

• Until the memory is exposed to electric charge, the content will be there forever.

4. Secondary memory

• It is connected to the computer externally to add additional functionality.