Computer Systems

software ports

Software ports are also used in computer systems. These are non-physical ports and are completely different from hardware ports. They allow multiple software applications to use different software ports on the same physical connection

Solid state

Solid state technology is used in storage media such as USB flash memory sticks. The technology is called solid state as it does not have any moving parts, such as a read-head in magnetic storage.

hardware ports

In computer hardware, a port serves as an interface between the computer and other computers or devices. this is usually in the form of a plug or wire

The fetch-decode-execute cycle

1. The next instruction is fetched from memory into the control unit. 2. This instruction is then decoded to determine the action that needs to be carried out. 3. The instruction is executed.

Command Line Interface (CLI)

A Command Line Interface is an entirely text-based interface that allows a user to communicate with a computer system by typing in commands. However, computer systems will only execute specific commands that are predefined. pros: • Quicker to type commands • Quicker to input commands as shortcut keys can be used • Little memory and processing power needed compared with other interfaces cons: • Very confusing for someone who has never used a command line interface • Commands have to be typed precisely. If there is a spelling error the command will fail

Graphical User Interface (GUI)

A GUI is a type of interface that allows users to interact with a computer system through graphical icons. Features: • windows • icons • menus • pointers • shortcuts/hot keys pros: • Easy to navigate • No complicated commands cons: • Requires a large amount of memory • Computing experts may find a GUI slower than a command line interface

CPU Cores

A core is the term used to describe the processing components within the CPU. Multi-core processors therefore have many processing components within the same CPU. In a single-core CPU each instruction is processed one after the other, whereas in a dual-core CPU, two instructions may be processed at the same time. In theory,a dual-core CPU should be able to process instructions twice as fast as a single-core CPU. However, this isn't always the case as sometimes Instruction 2 may need the result of Instruction 1 before it can be processed.

Registers

A register is a storage location found on the CPU where data or control information is temporarily stored. Registers are usually much faster to access than internal memory, since they have to be accessed so often

Buses

Buses allow data to be transferred to different parts of the computer. There are three main buses used by the CPU. there are three buses: the address bus, data bus and the control buss

Internal memory

Internal memory is fast access temporary storage on the CPU. Data is moved from the registers to the internal memory when it is not being actively used. Data from internal memory can then either be written to RAM or called back into the registers for further processing. This process of using internal memory speeds up the processing of data.

Complex Instruction Set Computer (CISC)

CISC processors can process a large number of complex instructions. This allows the processor to understand and carry out complex tasks with only a few instructions. The advantage of this is that a CISC processor is able to process complex instructions, without having to break them down into many simpler instructions. Processing complex instructions however requires more circuitry to decode and execute these instructions, which in turn means more power consumption and therefore more heat being generated.

Size of cache

Cache memory is a fast access type of memory that is very expensive.. Cache memory improves the performance of the CPU as it is able to provide instructions and data to the CPU at a much faster rate than other system memory such as RAM. The more cache memory your system has, the better its performance is likely to be.

Cache memory

Cache memory is used for the temporary storage of frequently accessed data and instructions. It consists of a small number of store locations that can be accessed very quickly by the CPU; it is quicker than RAM. Cache memory is volatile - this means that data is lost when the power is switched off.

Flash memory

Flash memory is used for the permanent storage of data. However, the data stored in flash memory can be changed. Flash memory is permanent - data is not lost when the power is switched off.

Optical

Optical storage media uses technology such as lasers. Laser beams are projected onto a CD/DVD or Blu-ray disk and if light is reflected back, then data is read as a 1 and if light is not reflected back, data is read as a 0. Lasers can be used to read and write information to a disk

Random Access Memory (RAM)

RAM is used for the temporary storage of currently running programs and data. It consists of a large number of store locations each of which is identified by a unique address. The data in each store location can be changed. RAM is volatile - data is lost when the power is switched off.

Reduced Instruction Set Computer (RISC) processors

RISC processors can process a limited number of relatively simple instructions. To carry out more complex commands the problem is broken down into a longer list of simpler instructions. The advantage of this is that a RISC processor is able to process these simpler instructions quickly. Processing simpler instructions also requires less circuitry to decode and execute these instructions, which in turn means less power consumption and therefore less heat being generated.

Read-only Memory (ROM)

ROM is used for the permanent storage of data. The data in each store location cannot be changed. ROM is permanent -data is not lost when the power is switched off.

Underclocking

Some computer systems, especially mobile devices, set the clock speed of the CPU lower than its original design. This results in less power consumption, less heat being produced and will therefore increase the battery life of the device.

Storage in the cloud

Storage in the cloud is a contemporary data storage facility that allows users to store their data on third-party servers. They can then access that data from many computing devices. There are many advantages to this, such as maintenance tasks, backup and data replication A disadvantage of storage in the cloud is that an Internet connection is required

Arithmetic and logic unit (ALU)

The ALU is the part of the CPU that processes and manipulates data. It performs simple calculations on the data that is temporarily stored in the registers. Examples of calculations that an ALU might perform are addition and subtraction.

Overclocking

The clock speed inside the CPU can sometimes be changed. A processor can be set to run faster than its original design. By doing this however, it uses more energy and produces more heat. If this heat is not removed through cooling, the CPU can overheat, which will damage the CPU and shorten its lifespan.

the controller

The controller sends and receives signals from all parts of the computer. This ensures that all processes take place at the right time and in the correct order. These signals travel along a control bus.

Speed of clock

The speed at which a processor operates is called the clock speed. The faster the clock speed, the faster the computer is able to run the fetch-decode-execute cycle and therefore process more instructions. The speed of the processor is measured in Hertz (Hz). One clock tick per second would be measured as 1 Hz. A modern day home computer would have a 2.5 GHz processor. This means the clock speed of the processor runs at 2,500,000,000 Hz or clock ticks per second.

Magnetic

This technology is used in floppy disks, hard disks and tapes. Data is stored on a magnetic medium, which can be a disk or a tape, by writing data using a write-head. Data can then be read by the read-head

Menu driven

This type of interface allows people to interact with a computer system by presenting the user and allowing them to work through a series of menus. pros: • No need to learn a lot of commands • Intuitive/easy to understand • Easy to navigate cons: • Irritating if there are too many menu screens to work through - users get annoyed or bored if it takes too long

Touch Sensitive Interface

Touch sensitive interfaces are becoming more popular and are extensively used in mobile computing devices. Commands are issued or data is input by touching the screen with your finger or a stylus pen. As well as tapping the touch sensitive screen, the screen can interpret other actions made by the user, such as pinching and swiping. pros: • Easier to use as the user simply touches what is seen on the display • No keyboard or mouse is required cons: • Screen can be easily damaged/scratched • Dirty screens are difficult to read

Voice-driven

Voice driven interfaces, also called voice recognition, can be used to issue commands to a computer system and enter data into it. pros: • Speech input is much faster than keyboard input • No need to learn to type cons: • Background noise interferes with speech recognition

Address bus and data bus

When data is saved or loaded from memory, the address at which it is to be stored or loaded from must be sent. The storage address of data always travels along an address bus. Data will then need to be moved between several parts of a computer. The path along which data travels is called a data bus.

Output devices

allows data to be given back to the user - speaker - monitor - printer

Input Devices

allows data to be put into the system - keyboard - mouse - microphone

The CPU

processes data and instructions made of subcomponents: • controller • ALU: arithmetic/logic unit • registers • internal memory • buses