1.3 Input, Output & Storage

• Processors:

  • A processor is a special component that processes data and instructions to control other components within the computer.
  • The two main types of processor are:
  • Central Processing Unit (CPU).
  • Graphics Processing Unit (GPU).
• Input/Output (I/O) devices

  • I/O devices allow users to input data into the computer, or receive a data output from the computer.
  • Examples of common I/O devices are:
  • Keyboard.
  • Mouse.
  • Monitor.
  • Speakers.
• Primary Storage:

  • Primary storage is the memory in which the computer can store the data or instructions that are currently in use.
  • The two main types of primary storage are:
  • Random Access Memory (RAM).
  • Read-Only Memory (ROM).
• Secondary Storage:

  • Secondary storage is the memory in which the computer can store the data or instructions which are NOT currently in use.
  • Not all computer systems use secondary storage.
  • The main types of secondary storage are:
  • Hard Disk Drive (HDD).
  • Solid State Drive (SSD).
  • Compact Disk (CD).
  • Flash (USB Drive).
• Data or instructions that are currently in use will be kept in the primary storage. The two main categories of this kind of storage are Random Access Memory and Read-Only Memory.
• General Purpose Systems:

  • General purpose systems are capable of performing many different tasks.
  • For example:
  • PCs
  • Macs
  • Smartphones
• Embedded System:

  • An embedded system is a computer system which is built into another device to support its operation.
  • For example:
  • Washing machines.
  • Digital cameras.
  • Sat-Navs.
• General purpose systems are capable of performing many different tasks.
• Storing a bit: (magnetic storage)

  • The value of each bit of data (0 or 1) is represented as a positively or negatively charged magnetic particle.
  • These particles are part of a magnetic disk called the platter.
• Accessing data (magnetic storage):

  • Data could be stored anywhere on the disk, and so to read/write data we first need to find the location on the disk.
  • A magnetic read/write head is used to access the data while the platter spins.
• Reliability (magnetic storage):

  • The HDD has moving parts.
  • Although the HDD is generally reliable, any device with moving parts will be subject to wear-and-tear.
  • HDDs can also be damaged by shocks. They are not robust.
• Magnetic Storage:

  The value of each bit of data (0 or 1) is represented as a positively or negatively charged magnetic particle.
• Hard Disk Drives:

  • generally reliable
  • secondary storage devices
  • subject to wear-and-tear
• properties of magnetic media:

  • low cost
  • low speed
  • high capacity
  • good reliability
• Magnetic media is not robust because it has a lot of moving parts.
• • Magnetic media is very low cost per unit capacity.
  • This makes it an economical choice for storing large amounts of data.
• • Magnetic media needs a high number of moving parts.
  • The high number of moving parts make magnetic media slow to access.
• • Magnetic media can store a large quantity of data in a compact way.
  • This makes them a popular choice for archives as well as home computers.
• • Magnetic media is reliable and tends to last for a long time.
  • Magnetic media is not robust, and tends to break on impact or during vibrations.
• Magnetic tape:

  • Magnetic tape used to be popular for distributing content such as:
  • Audio.
  • Video.
  • Software.
  • Nowadays, tape is only used for:
  • Some video cameras.
  • Making backups.
• Hard Disk Drives (HDD):

  • HDDs are often used as the main form of secondary storage in a computer system.
  • HDDs hold the operating system, applications, and user data.
• Hybrid drives:

  • Some modern devices have both magnetic and solid state storage.
  • The combination of magnetic and solid state storage is known as a hybrid drive, and offers the benefits of both systems.
• Magnetic tape used to be used to distribute content. Now, the main purpose of magnetic tape is to make backups.
• Before optical media and the Internet, content used to be delivered by magnetic tape.
• Blu-ray Disks (BD): (optical storage)

  • Blu-Ray disks are often used to store high definition movies or games.
  • A single Blu-Ray disk can store around 25 GB of data.
• Compact Disk (CD): (optical storage)

  • CDs are the original optical media standard.
  • A single CD can store around 700 MB of data.
  • CDs are very cheap to produce.
• Digital Versatile Disk (DVD): (optical storage)

  • DVDs are often used to store games or standard-definition movies for home viewing.
  • A single DVD can store around 4.7 GB of data.
• Types of Optical Disk:

  Re-writable (RW)

  • A CD-RW, DVD-RW, or BD-RW is a disk which can be overwritten whenever the user would like to.
  • These are often used for backups which might need to be updated in the future.
• Types of optical disk:

  write-once (R)

  • A CD-R, DVD-R, or BD-R is a disk which can be written once by the user at home.
  • Once the user has written data to the disk, they cannot overwrite it.
• Types of Optical Disk:

  Read-only-memory (ROM)

  • A CD-ROM, DVD-ROM, or BD-ROM is a disk which can be read only.
  • The manufacturer writes the initial data, and this cannot be changed.
  • This is often used in content distribution so that people cannot accidentally overwrite the content.
• ROM is usually used to distribute games or movies
• DVD's are often used to store standard-definition movies
• A single CD can store 700MB
• General purpose computers usually contain a large amount of RAM.
• Random Access Memory (RAM) is one of the two types of main memory found in computers.
• RAM is much faster to access than secondary storage such as Hard Disk Drives (HDDs).
• • Random Access means that any part of the memory can be accessed non-sequentially and as quickly as any other part of the memory.
• RAM is much more expensive per unit capacity than secondary storage media.
• • RAM is volatile. This means that it will lose its contents when power is lost (i.e. if the computer is switched off).
• General purpose computers usually contain a large amount of Random Access Memory (RAM).