1. COMPUTER MEMORY
Presented by:
ANUJ SHRESTHA

2. MEMORY HIERARCHY
Memory
Primary Secondary Cache
RAM ROM Hard Disk,
Magnetic
Tape,
Static PROM CD, DVD, Zip
Disk etc
Dynamic EPROM
EEPROM

3. PRIMARY MEMORY
 Provides storage for data and instructions on which
control unit and arithmetic logic unit can operate.
 Data or instructions entered through input device is
stored in it.
 Holds the program and data currently being used
for computer and also stores intermediate results.
 Operates at the highest speed and can be access
directly by central processing unit(CPU).

4. TYPES OF PRIMARY MEMORY
 Random access memory(RAM)
 Read/write memory
 Place in a computer where operating
system, application programs, and data in current use
are kept for quick access
 Data stays only as long as the computer is running
 2 types
 Static RAM(SRAM)
 Dynamic RAM(DRAM)

5. TYPES OF PRIMARY MEMORY (CONT.)
 Static RAM(SRAM)
 Stands for Static Random
Access Memory
 Retains the data as long as
power is provided to the
memory chips
 Doesn’t need to be
‘refreshed’ periodically.
 Very fast and expensive as
compared to DRAM.
 Used in specialized
applications in computer.

6. TYPES OF PRIMARY MEMORY (CONT.)
 Dynamic RAM(DRAM)
 Stands for Dynamic
Random Access Memory
 Must be continually
‘refreshed’ in order for it to
maintain the data
 Cheaper and smaller than
SRAM
 Used as system memory
in most of the computers

7. TYPES OF PRIMARY MEMORY (CONT.)
 Read Only Memory(ROM)
 Permanent memory
 Contents are not lost when the power
supplies are switched off.
 User can’t write in it
 Stores permanent programs and other types of
information needed by computer to execute users
programs

8. TYPES OF PRIMARY MEMORY (CONT.)
 Types of ROM
 Programmable Read Only Memory(PROM)
 Program stored in PROM can be modified once by the user.
 Once chip has been programmed, recorded information cannot
be changed
 Erasable Programmable Read Only Memory (EPROM)
 Can be erased and reprogrammed
 Needs to be removed from the proccessor and exposed to
ultraviolet light for sometime before it can accept any new
contents.

9. TYPES OF PRIMARY MEMORY (CONT.)
 Electrically Erasable Programmable Read Only Memory
(EEPROM)
 User-modifiable read-only memory (ROM) that can be erased
and reprogrammed (written to) repeatedly through the
application of higher than normal electrical voltage generated
 Limited to single byte operations which made them slower
 Retains it’s contents even when the power is turned off.

10. QUERIES??