Computer systems and The CPU

The purpose of a computer is to take data, process it and output it.Complete tasks more efficiently than humans. Hardware- Physical stuff CPU, Motherboard, monitor, and printer.

The software is the programs or applications that a computer system runs e.g an operating system, a word processor.

The range of computer Systems. Dedicated systems (designed for one particular purpose traffic lights) or calculators or large supercomputers. General purpose performs many tasks e.g PCs.

Embedded systems

A computer built into other devices. Often used as control systems they monitor and control machinery in order to achieve the desired result. E.g in a dishwasher the embedded system could control water pumps.

Cheaper to produce and design. More efficient at doing their task than a general computer.

Ram - High-speed Volatile Memory It is used as the main memory in a computer. It can be read and written to. Ram is volatile. Temporary memory. It needs the power to retain its data. Nonvolatile is a permanent memory.

The operating system is copied from secondary storage to RAM. When software applications documents. They are copied 2ndary to Ram they stay in RAM until the files or applications are closed. Ram is slower than the CPU cache but way faster than secondary storage.

The Virtual Memory- Limited amount of RAM. Application opens so RAM fills with data. When RAM is full the computer moves data that hasn't been used recently to virtual memory. May be needed if there are too many applications open at once or if memory intensive program. 

CPU needs to read data stored in virtual memory so it moves it back to RAM. Data transfer rates are much slower. Using virtual memory can make switching between applications slow. Constant moving between virtual memory and RAM just to keep the program running. 

Primary Storage - areas that the CPU can access very quickly like CPU registers cache ROM and RAM. Fastest read-write speeds.

Secondary Storage- non-volatile where operating systems and applications are stored when not in use.E.g Magnetic hard disk drives, SSD, and CDs. Much slower than primary storage.

Tertiary storage is non-volatile and used for storing data more long term. Archives and backups.Magnetic tape library

OS Functions- Internal and External Hardware. 

Provide user interface so the user can interact with the computer. Provide a platform for different applications to run. Allow the computer to multi-task by controlling memory resources. Deal with File management.

Device Drivers - Drivers act as translator for signals between OS and hardware. OS and mouse.

User Interface- allows the user to interact with a computer system. GUIs are the most common type they're designed to be easy for everyday users by making them visual.  Systems are optimized for specific input methods. Android was created for touchscreen devices. using finger gestures. 

Command lien interface is text based. Command-line interfaces are less resources-heavy than GUIs. For advanced users, they can be far more efficient and powerful than a GUI. Used to automate processes.  

Multi- Tasking - Multi-tasking CPUs.Provide a platform to run applications. When an application is opened the OS moves the necessary parts of the application to memory. The OS will decide if applications or features have been used recently if not removed from memory. 

To run multiple applications OS needs to make sure that applications don't overwrite or interfere with each other.Memory manager allocates certain applications certain memory addresses.          Only one application is processed by the CPU at a time other processes must wait. OS divides CPU time between open applications efficient order.OS can also move data to and from virtual memory.

Os is responsible for file management organization of data. Manages Hard Disk

OS is responsible for user account control. Allows different users to be granted access to specific data. Anti-theft measures: pin protected or password. 

Defragmentation puts broken up files back together it reorganizes data on the hard drives. When files are moved or deleted and change size lot of small gaps appear on the disk.This causes the disk to fragment. reading and writing files are slower. 

SSD's use flash storage with no moving parts fragmentation doesn't cause any problems.

Backup is a copy of systems files and settings stored externally. This means data can be recovered in the event of data loss. Fire, theft malware. A full backup is where a copy is taken of every file on the system. A lot of storage space. Long time to create but faster to restore from.

Incremental backup - Only files edited from the last backup are copied. Use less storage but full restore is slow.

Compression Software-- reduces the size of files so they take up less space.Used on internet..zip and . rar. Need to be extracted before use. Encryption software scrambles data to stop 3rd party people accessing it. Can be decrypted using the special key.