section 1 - components of a computer system Flashcards
Embedded systems
- embedded Systems are computers built into other devices, like dishwashers, microwaves and washing machines - It’s used when the bigger machine has a restricted set of instructions that are unlikely to change.
CPU
Processes all the data and instructions required to make the system work. Central Processing unit
CPU - Clock speed
This is the number of instructions a single processor core can carry out per second (Hz). For most desktop computers, this will be somewhere around 3.5 GHz (3.5 billion instructions per second). .The higher the clock speed, the greater the number of instructions that can be carried out per second.
Some CPUs can be overclocked to make them run at a higher clock speed than the factory-set rate. But it’s risky if not done properly - it can make CPUs overheat, causing crashes or permanent damage to the system. High performance cooling systems (e.g. water cooling) are usually needed.
CPU - number of cores
Each core in a CPU can process data independently of the rest. * The more cores a CPU has, the more instructions it can carry out at once, so the faster it can process a batch of data.
* Most PCs and smartphones have 4 or more cores these days.
CPU - cache size
- The cache is data storage inside the CPU that’s much faster than RAM. * A larger CPU cache gives the CPU faster access to more data it needs to process.
More RAM can mean a Faster or Smoother System
1) If a computer has too little RAM it may run slowly due to the use of virtual memory
2) The more RAM, the more applications, or more memory-intensive applications it can smoothly run, making it faster overall.
3) It’s easy to upgrade RAM on a PC or laptop - it’s just a matter of replacing the RAM sticks with higher capacity (or higher speed) ones.
4) If the computer already has plenty of RAM to run everything the user wants, increasing RAM may make no difference to performance.
GPUS help CPUs process Images.
1) GPUs (graphics processing units) are specialised circuits for handling graphics and image processing. They relieve the processing load on the CPU, freeing it to do other things.
2) Computers have basic GPUs integrated onto the motherboard or the CPU. For better graphics performance, a dedicated GPU (graphics card) is often used.
3) Using high-end graphics cards can greatly improve performance in graphics-intensive applications, e.g., PC gaming and design software.
Volatile memory
Volatile memory is temporary memory. It requires power to retain its data.
Non-volatile
Non-volatile is permanent memory it keeps its contents even when it has no power.
RAM
RAM is High Speed, read, write, Volatile memory.
1) RAM (or Random Access Memory) is volatile memory with fast access speeds
2) contains all data, files and programs, and the OS while they’re being used.
3) When a computer boots up, the operating system is copied from secondary storage to RAM.
virtual memory
Virtual memory is the use of secondary storage as extra RAM when the ram is full.
much slower than RAM
When RAM is full, the computer moves data that hasn’t been used recently to a location on secondary storage which is known as virtual memory.
If the CPU needs to read data stored in virtual memory, it must move the data back to RAM. This is slow as data transfer rates are much slower on secondary storage than RAM.
ROM
1) ROM (Read Only Memory’) is non-volatile memory.
2) ROM comes on a small, factory-made chip built into the motherboard.
3) It contains all the instructions a computer needs to properly operate. These instructions include the BIOS (Basic Input Output System), POST (Power on Systems Test) and the bootstrap.
4) As soon as the computer is powered on, the CPU reads the instructions from ROM. This tells the CPU to perform self-checks and set up the computer, e.g., test the memory is working OK, see what hardware is present and copy the operating system from secondary storage into RAM.
3 types of storage
- Primary storage
- Secondary storage
- Tertiary storage
Primary storage
Primary storage refers to the memory areas that the CPU can access very quickly, like CPU registers, cache, ROM and RAM. Primary storage has the fastest read/write speeds and is mostly volatile
Secondary storage
Secondary storage is non-volatile-it’s where all data (operating systems, applications, and user files) are stored when not in use. It includes magnetic hard disk drives, solid state drives, CDs, and SD cards. Read/write speeds are much slower compared to primary storage.
Tertiary storage
Tertiary storage is used for long term data storage (it’s mainly uses for archives and back-ups of massive amounts of data)
Solid State Drives
1) Solid State Drives (SSDs) are storage devices with no moving parts. SSDs are used for the same purpose as HDDs for internal/external storage.
2) Most SSDs use a type of flash memory (a common type of non-volatile memory).
3) SSDs have significantly faster read/write times than HDDs.
Hard Disk Drives
A hard disk drive is made up of a stack of magnetised metal disks that spin thousands of times a second.
Data is stored magnetically in small areas on the disk’s circular tracks.
A moving arm can access these areas and read or write data.
Despite their moving parts, HDDs are generally very long lasting and reliable, although they could be damaged by large impacts like being dropped.
Hybrid drives
Hybrid drives exist which use solid state storage for the OS and programs, and a hard disk for data.
portable high capacity storage
Portable HDDs & SSDs are popular for backing up and transporting large amounts of data.
Other types of flash storage
USB pen drives and memory cards (e.g., SD cards) are also flash-based, solid-state storage.
They’re much slower than SSDs and have a much shorter read/write life. They’re used to expand the storage capacity of small devices like cameras, smartphones, and tablets (which are too small for SSDs or HDDs). Their capacity is very high relative to their tiny size.
Advantages of HDDs
HDDs are cheaper.
Both are high capacity, but HDDs are higher.
HDDs have a longer read/write life than SSDs - SSDs can only be written a certain number of times before they begin to deteriorate.
Advantages of SSDs
SSDs are faster.
SSDs don’t need defragmenting.
SSDs are more shock-proof than HDDs.
HDDs make some noise, SSDs are silent.
optical discs
Optical discs are things like CDs, DVDs, and Blu-ray discs.
CDs can hold around 700 MB of data, DVDs can hold around 4.7 GB and Blu-rays can hold around 25 GB.
Optical discs come in three forms:
-read-only (e.g., CD-ROM/DVD-ROM/BD-ROM)
-write-once (e.g., CD-R/DVD-R/BD-R)
-rewritable (e.g., CD-RW/DVD-RW/ BD-RW)
Data is stored as microscopic indentations (pits) on the shiny surface (lands) of the disc.
magnetic tapes
Magnetic tapes are often used by large organisations in archive libraries to store huge amounts of data.
It comes in plastic cassettes (containing reels of tape). Cassettes require a special tape-drive for read/writing.
Tape is read/written sequentially, meaning it is read/written from the beginning to the end. This means tape is very slow when finding specific data stored on it, but has a fast read/write speed once it is in the correct place to begin reading/writing.
Criteria for assessing storage suitability.
- Speed Mbps
- Capacity GB
- cost per GB
- resiliency
- portability
- durability
- environmental
- noise
Summary of relative speeds cost and capacities of all these different types of storage
Main Functions of an OS
- Communicate with internal and external hardware via the device drivers.
- Provide a user interface, allowing a user to interact with the computer.
- Provide a platform for different applications to run.
- Allow the computer to multi-task by controlling memory resources and the CPU.
- Deal with file management and disk management.
- Manage the security of the system, e.g., through user accounts.
Device Drivers
- Every piece of hardware connected to the computer system requires a device driver. Drivers essentially act as a ‘translator’ for the signals between OS and hardware.
- the OS will choose the correct device drivers for the hardware it detects. If new hardware is connected to the computer, the system will install the new, matching driver.
- Device manufacturers may release updates to device drivers to fix bugs, add features or improve the performance of their hardware. Updates may be installed automatically by the OS or manually by the user.
command-line interface CLI
A command-line interface is text-based. The user enters specific commands to complete tasks. Command-line interfaces are less resource-heavy than GUIS. Command-line interfaces aren’t suitable for everyday users. But for advanced users, they can be far more efficient and powerful than a GUI. They can be used to automate processes using scripts (simple programs).
Graphical User Interfaces (GUIs)
Graphical User Interfaces (GUIs) are the most common type – they’re designed to be easy for everyday users by making them visual, interactive, and intuitive. GUI systems are optimised for specific input methods. In the past, GUIs have been WIMP-based (using windows, icons, menus, and pointers). Android and iOS were created for touchscreen devices, using finger gestures like pinching, and swiping in place of a mouse.
multi-tasking OSs.
Operating Systems that can run multiple applications at the same time are called multi-tasking OSs.
How does the OS allow multi-Tasking
The OS helps the CPU carry out multi-tasking by efficiently managing memory and CPU processing time:
-When an application is opened, the OS moves the necessary parts of the application to memory, followed by additional parts when they are required. The OS will decide if applications or features have been used recently - if not, they may be removed from memory.
-When required, the OS organises the movement of data to and from virtual memory.
To run multiple applications, the OS needs to make sure that the applications don’t overwrite or interfere with each other. A memory manager allocates certain applications certain memory addresses, to make sure their processes are placed into separate locations.
-Only one application is processed by the CPU at a time, so the other processes must wait. The OS divides CPU time between open applications and may prioritise certain processes for instructions to be executed in the most efficient order.
The OS handles File and Disk Management
The OS is responsible for file management - the organisation of data into a usable hierarchical structure.
The OS may also include utility software (e.g file explorer for windows) to help it manage files and disks. File compression software can reduce the size of individual files and encryption software is used to secure the contents of files. Defragmentation software can help to organise and maintain the hard disk by collecting all the free space together.
Single-user OS’s
Single-user operating systems allow only one user to use the computer at once. Most common OS’s, such as macOS, are single-user operating systems, even if the computer has multiple user accounts, or is connected to a network (see p.34).
Multi-user OS’s
Multi-user OS’s (e.g., UNIX® server) allow several users to use the computer at the same time. They’re often used on mainframes (huge supercomputers) and give many users simultaneous access. For example, ATMs allow thousands of people access to a large bank’s mainframe at the same time.
Defragmentation Utilities software
1) Files are stored on a hard disk in available spaces. Ideally, entire files would be stored together.
2) However, as files are moved, deleted, and change size, lots of small gaps begin to appear on the disk. When writing files to the disk, the OS splits files into smaller blocks to fill up the gaps.
3) Over time, the disk becomes more and more fragmented. This makes reading and writing files slower as the read/write head must move back and forth across the disk.
4) Defragmentation software reorganises data on the hard drive to put fragmented files back together. It also moves files to collect all the free space together. This helps to prevent further fragmentation.
5) As SSDs use flash storage with no moving parts, fragmentation doesn’t cause them any problems - they can access data just as quickly however it’s arranged. In fact, as SSDs have a limited number of read/writes, defragmenting them can actually shorten their lifespan.
Encryption Software
1) Encryption software scrambles (encrypts) data to stop third parties from accessing it.
2) To decrypt the data, a special ‘key’ is needed. A computer uses the key and a set of instructions to turn the data back into its original form.
examples of utility software
text editors
antivirus
clipboard
encryption
compression software
backup software
defragmentation software
