1.2 Memory and Storage

primary storage

the main memory used by the CPU for immediate data processing

purpose of primary storage

to store programs that are currently running and need to be accessed by the CPU

two types of primary storage

RAM and ROM

RAM

Random Access Memory

type of volatile primary storage that stores data and instructions temporarily while a computer is running

purpose of RAM

Temporary Storage: Holds data and instructions that the CPU needs for current tasks.

Improves Speed: Enables quick access to active processes, improving system performance.

Supports Multitasking: Allows multiple applications to run simultaneously by storing active data.

characteristics of RAM

• Volatile: Data is lost when the power is turned off.

• Fast: Provides quick read and write access for active processes.

• Temporary Storage: Holds data and instructions in use by the CPU.

ROM

Read-Only Memory

type of non-volatile memory that stores permanent data and instructions.

characteristics of ROM

• Non-volatile: Retains data even when the power is off.

• Read-only: Data is typically written during manufacturing and cannot be modified (or is difficult to change)

purpose of ROM

• Stores the Bootstrap: The initial program that runs when the computer is powered on.

• Locates the OS: Tells the computer where to find the operating system on the hard drive.

• Holds BIOS: The Basic Input/Output System, which runs without a hard drive.

• Controls Configuration: Manages basic settings like processor speed and system time.

virtual memory

use of secondary storage (hard drive) as additional primary memory

purpose of virtual memory

to be used when the computer has no more available random access memory (RAM).

process of using virtual memory

• When RAM is full, part of the secondary storage (like the hard disk) is used to store data temporarily.

• Virtual memory moves unused data from RAM to the hard disk, freeing up space for other programs.

• When the data is needed again, it’s swapped back into RAM, and other unused data is moved to the hard disk. This process is called swapping.

cache

piece of temporary memory

can refer to a part of the RAM, storage disk, CPU, or an area for storing web pages

secondary storage8

the storage of data that is not accessed frequently as the data in primary storage

purpose/need for secondary storage

Needed to keep programs and data indefinitely. Without secondary storage all programs and data would be lost the moment the computer is switched off.

three types of secondary storage

magnetic, optical and solid state

data

units of information (eg integers, string, Boolean, characters)

general purpose computer

a computer designed to be able to carry out a wide range of instructions

types of magnetic storage

• hard disk drives (HDD)

• floppy disks

• magnetic tapes

types of optical storage

• CD-ROM/R/RW

• DVD-ROM/R/RW

• Blu-ray-ROM/R/RW

types of solid state storage

• solid-state drives (SSD)

• USB memory sticks

magnetic storage - a+d

advantages -

• fairly cheap

• high in capacity

• durable

disadvantages -

• susceptible to damage if dropped

• vulnerable to magnetic field (string magnetic could wipe device)

optical storage - a+d

advantages -

• cheap

• portable

• not prone to magnetic interference

• large storage amount

disadvantages -

• easily scratched, damaged or broken

• slow to access data

solid state storage - a+d

advantages -

• no moving parts; more durable

• faster access time

• require little power

• extremely portable

disadvantages -

• expensive

• less storage

• more prone to power loss and electromagnetic fields

factors that determine which storage medium is used

• Cost

• Speed of access

• Portability

• Durability

• Reliability

• Capacity