3.1 Computers and their components Flashcards
What is the difference between memory and storage?
Memory is usually referred to as the internal devices which the computer can access directly. This memory can be the user’s workspace, temporary data (RAM) or data that is key to running the computer (e.g. start=-up instructions - ROM)
Storage devices allow users to store applications, data and files. The user’s data is stored permanently (non-volatile) and can be edited and accessed at the convenience of the user.
Storage needs to be larger than internal memory since the user may wish to store large files (such as audio, video and images)
Storage devices can also be removable to allow data to be transferred between devices.
- HDD, SSD, removable devices
What is the difference between removable storage and internal memory
Removable devices allow a user to store important data in a different external device in case of data loss - DVD/CD/Blue-ray, flash memory stick, hard disk drive
Internal memory includes components such as registers (which are part of the processor)
There is also memory cache (which is external to the processor). This is used to store data which the processor will likely need to use again.
What are embedded systems?
Embedded systems involve installing microprocessors into devices to enable operations to be controlled in a more efficient way. Embedded systems have a dedicated function within a larger mechanical or electronic system.
- cookers, cruise control, refrigerators and central heating systems can now all be activated by a
web-enabled device (such as a mobile phone or tablet).
The time a central heating systems switches on or off and the temperature can all be set from an app on a mobile phone from anywhere in the world.
Benefits of embedded systems
• Small in size and therefore easy to fit into devices
• Relatively low cost to manufacture
• Usually dedicated to one task, making for simple interfaces and often no
requirement for an operating system
• Consume very little power
• Very fast reaction to changing input (operate in real-time)
• Reliability (product of mass production)
Drawbacks of embedded systems
• Difficult to upgrade devices to take advantage of new technology
• Troubleshooting faults in the device becomes a specialist task
• Although the interface can appear to be simple, in reality it can be more confusing
(changing the time on a cooker can take several steps, for example)
• Any device that can be accessed over the internet is also open to hackers, viruses, etc.
• Due to difficulty in upgrading and fault finding, devices are often just being thrown
away rather than repaired (wasteful)
Describe the principal operations of HDD
A HDD is a direct access device. Data is stored in a digital format on the magnetic surfaces of the disks (or platters, as they are frequently called) in allocated sectors, which will contain a fixed number of bytes which are read sequentially, and tracks. A HDD will have a number of platters which can spin about 7,000 time per second.
A number of read-write heads can access all of the surfaces in the disk drive. Normally each platter will have two surfaces which can be used to store data. Read-write heads can move from the centre of the disk to the edge (and back again) 50 times per second. Removable hard disk drives are essentially HDDs that are external to the computer and can
be connected using one of the USB ports. They can be used as back-up devices or as
another way of transferring files between computers.
What disadvantages are there to HDDs?
HDDs have very slow data access compared to RAM. Many applications require
the read-write heads to constantly seek the correct blocks of data, resulting in more head
movements and latency effects.
As the HDD undergoes numerous deletions and edits, which leads to segments of data being increasingly fragmented, resulting in the gradual deterioration of the HDD performance - although defragmentation software can improve on this situation by ‘tidying up’ the disk sectors.
What are SSDs?
Latency is an issue in HDDs, so solid state drives (SSD) reduce this issue considerably.
They have no moving parts and all data is retrieved at the same rate. They do not rely on magnetic properties.
The most common type of SSDs store data by controlling the movement of electrons within NAND chips (flash memory). Although a number of them sometimes used EEPROM chips, to erase data in byte-sized chunks not just blocks of data - faster but very expensive
The data is stored as 0’s and 1’s in millions of tiny transistors (at each junction, one transistor is called a floating gate and the other is called a control gate) within the chip. This effectively produces non-volatile rewritable memory.
What benefits are there to SSDs? and what is the main drawback?
- More reliable (no moving parts to break)
- Considerably lighter (suitable for laptops)
- Do not have to ‘get up to speed’ before they work properly
- Have a lower power consumption
- Run much cooler than HDDs (both these points again make them very suitable for laptops)
- Slim/thin (because they have no moving parts)
- Access data considerably faster
The main drawback of SSDs is the still unknown longevity (average 3 years) of the technology. Servers do not use, manufacturers addressing these issues.
What are memory sticks/flash memory?
Memory sticks/flash memories (pen drives) use solid state technology. They usually connect to a computer through a USB port.
Their main advantage is that they are very small, lightweight devices which make them suitable for transferring files between computers or to be used as a dongle to prevent unauthorised use of software.
They can also be used as small back-up devices for music or photo files, for example.
