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.
