Memory (RAM and ROM)
Types of primary storage
In the Von Neumann architecture, primary storage is needed to store programs that
are currently running and need to be accessed by the CPU
The two types used as primary storage are:
RAM Random Access Memory
ROM Read Only Memory
RAM is often referred to as:
o Main memory, primary memory, primary storage
It can be read from and written to
o Access to RAM is much faster than a hard drive
o The name Random Access Memory comes from the ability of the
CPU to access any part of the memory in the same amount of
time
At any one time it will normally store:
o The operating system (of part currently in use)
o The software currently in use
o The data which the software is using
The computer stores running programs and data in RAM when your computer is
turned on
When your computer is turned off, data stored in RAM is lost
o RAM is volatile as it loses data if the power is off
All your programs and data are stored permanently on your hard drive
o This is known as non-volatile storage as it doesn’t lose the data if
the power is off
1
,What is the difference between ROM and RAM? (2 marks)
RAM is volatile, whereas RAM is non-volatile.
Random access memory (RAM)
When applications or programs are loaded, they are copied into RAM
from the hard drive
o Documents and files (data) that are used with those programs
are also opened by copying them into RAM
o RAM starts to fill up as all these programs, documents and files
are copied
Virtual memory is part of the hard drive used as an extension to RAM
Advantages:
Uses cheap secondary storage on the hard drive
Prevents error messages saying “out of memory” — the programs and files
will still open
Disadvantages:
Accessing virtual memory is very slow
To access data, the existing data in RAM needs to be copied to the virtual
memory, then data in virtual memory needs to be copied to RAM
Read-only memory (ROM)
Some data needs to be permanently held in primary storage, even when a
computer has no power
o Read-only memory (ROM) is used to store this data
o Data is read from ROM, but cannot be written to it
o It is non-volatile as the data isn’t lost if the power is off
Characteristi RAM ROM
cs
2
, Size Typically 4 GB - 32 GB Typically 4 MB to 8
MB
Used to store Running programs and operating BIOS and bootstrap
system
Read ability Yes No
Write ability Yes No
Volatile Yes No
3
Types of primary storage
In the Von Neumann architecture, primary storage is needed to store programs that
are currently running and need to be accessed by the CPU
The two types used as primary storage are:
RAM Random Access Memory
ROM Read Only Memory
RAM is often referred to as:
o Main memory, primary memory, primary storage
It can be read from and written to
o Access to RAM is much faster than a hard drive
o The name Random Access Memory comes from the ability of the
CPU to access any part of the memory in the same amount of
time
At any one time it will normally store:
o The operating system (of part currently in use)
o The software currently in use
o The data which the software is using
The computer stores running programs and data in RAM when your computer is
turned on
When your computer is turned off, data stored in RAM is lost
o RAM is volatile as it loses data if the power is off
All your programs and data are stored permanently on your hard drive
o This is known as non-volatile storage as it doesn’t lose the data if
the power is off
1
,What is the difference between ROM and RAM? (2 marks)
RAM is volatile, whereas RAM is non-volatile.
Random access memory (RAM)
When applications or programs are loaded, they are copied into RAM
from the hard drive
o Documents and files (data) that are used with those programs
are also opened by copying them into RAM
o RAM starts to fill up as all these programs, documents and files
are copied
Virtual memory is part of the hard drive used as an extension to RAM
Advantages:
Uses cheap secondary storage on the hard drive
Prevents error messages saying “out of memory” — the programs and files
will still open
Disadvantages:
Accessing virtual memory is very slow
To access data, the existing data in RAM needs to be copied to the virtual
memory, then data in virtual memory needs to be copied to RAM
Read-only memory (ROM)
Some data needs to be permanently held in primary storage, even when a
computer has no power
o Read-only memory (ROM) is used to store this data
o Data is read from ROM, but cannot be written to it
o It is non-volatile as the data isn’t lost if the power is off
Characteristi RAM ROM
cs
2
, Size Typically 4 GB - 32 GB Typically 4 MB to 8
MB
Used to store Running programs and operating BIOS and bootstrap
system
Read ability Yes No
Write ability Yes No
Volatile Yes No
3
