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Computer Systems

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Harry Watt

on 29 June 2014

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Transcript of Computer Systems

How does the CPU work when you give it an instruction?
Input Devices
Input, Processing, Output and Storage
Computer Systems
By Harry Watt and Katie Henderson
A Computer System is a system that is able to take a set of inputs, process them and create a set of outputs. This is done by the combination of hardware and software.

A computer system uses inputs to provide data. This data is then processed by the CPU (Central Processing Unit). The outcome of processing can be sent to outputs or stored in storage.

For processing to take place, there needs to be a set of instructions of what needs to be done. This set of instructions is called a programme.

In this presentation, we will talk about different types of input, processing, storage and output devices and how these devices operate.
A mouse is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface.
The mouse usually consists of 2 buttons and 1 scrolling wheel which can be used for more controlㄷㅌㅅㄱㅁ ㅠㅕㅅ세ㅐㄷㄷㅌor dimensional input.

The mouse converts the movements of our hand into binaries so the information processing system can receive and process the information.
A keyboard is an input device because when you want to type on the keys on the keyboard the information turns into signals (binaries) and is sent to the computer to produces letters, numbers or signs. Therefore a keyboard is commonly used to give commands to the operating system of the computer.
A touchscreen is an electronic visual display that the user can control through simple or multi-touch gestures by touching the screen with one or more fingers. The user can use the touchscreen to react to what is displayed and to control how it is displayed (for example by zooming the text size).

When someone touches the touchscreen, two layers inside the glass panel make contact. The change of the electric field is noted and the device coordinates the spot. This is then traslated into electric signals (binaries) and sent to the operating system.
Web-cams work with the computer systems' video card and operating system. They work together with an image sensor to capture the video. The electronics also work together to read every image and send or 'transmit' it to the hard drive.
A microphone is a very widely used input device. What it does is it changes sound waves (when you speak into it) into electrical energy. The main component to allow it to do this is the diaphragm. This is a small, thin piece of material such as paper or aluminum. The diaphragm vibrates when it's hit by the sound waves, and these vibrations then transform into electrical signals, which then become the audio signals.
The Central Processing Unit
Scanner is a device that optically scans images, text or an object, and converts them into digital images. It is most often used in offices for scanning documents.

When a document is placed on the glass panel in a scanner, mirrors reflect the light onto the lens, which then focuses the image through a filter on a sensor.

This image is then transfered into binaries and sent to the processing system.
Barcode Scanner
Each and every barcode has its own unique series of bars and numbers, Every barcode's numbers and bar sizes and widths are different. The scanner's photosensors read the individual numbers and bars, and then transfer them into electrical signals or 'pulses' like most input devices. Due to every strip of bar is acting as a character, the barcode's software then simply turns them into readable text and displays it on what ever system it is connected to. This all happens in a matter of milliseconds.
An input device can be ANY device or electronic that is used to insert data or supply information for the computer or infact any other computing related device!
A joystick is an input device that consists of a stick that pivots on a base and tells the computer system which angle or direction it's moving. These are used on PS3 and XBOX360 conrollers and other modern gaming devices. It is also commonly known as an 'analog' stick.
Which input devices might we have in the...
On-body interactive surface
In the future, many scientists are speculating for an on-body interactive system to come into play. Although this feature is still being researched, many videos like the one below named 'skin put' have been tested. This system uses 'transverse' waves that we can see moving on the skins surface. This video shows how it works, how accurate it is and if it is possible to be a future technology.
Eye Control
Eye control is a very realistic insight of what the future might consist of. This is because, although hard to design, it is very easy to use. Just a blink or movement of the eye controls the system it's connected to. In the short video below, it shows how Windows 8 has already included this feature. This is just a basic view of what eye control may be able to do in the near future.
Brain-Computer Interface
Brain-Computer interface is a direct communication pathway between the brain and the computer. This enables us to input information without using any devices such as mouse or keyboard because it detects our thoughts and sends informaion to the processing system.

This is an incredibly useful techonology to physically disabled people. People who cannot speak or cannot use their hands for typing will be able to communicate with others easily.

This will be also useful for ordinary people. This will save time, effort and guarantee the privacy. For example, when you don't want the people around you to listen to your personal call, you can use the brain-computer interface to activate 'voicelss call'. This will capture the activity you want to do by detecting the movements of neurons in the brain and translate it into speech. This YouTube video shows how it works.
A Central Processing Unit ( CPU ) is the hardware within the computer which carries out the instructions of computer program. CPU is composed of the processor and the RAM (Random Access Memory).

When a program runs on a computer it is loaded into the RAM. From here, each instruction can be accessed by the processor. After the instructions are fetched, they are then decoded and executed by the processor.

The CPU is the brain of the computer, so it's the most important element of a computer system in terms of computing power.
The fundamental operation of the processor is to execute a sequence of stored instructions called a program. There are four steps of operating a program - Fetch, Decode, Execute and writeback. These processes are repeated in a cycle called Fetch-Execute Cycle. This will be explained in details later.

The processor is the most important piece of device in the computer. It is where all the calculations and executions occur.

Today, the processors have been developed a lot and become tremendously faster. The average speed of the processor now is about 2.5GHz, which means it can execute 2.5 billion (2,500,000,000) instructions in one second.
ㄱㅁㄱ므Random Access Memory
Random Access Memory (RAM) is a form of computer data storage. It works as a temporary storage for data and programs, just for the duration of that program. Once the program has finished and is closed, it is no longer in the main memory.

The RAM is very important in processing because it is where all the running programs are temporarily saved. So the RAM with larger memory capacity is able to operate more programs at once.

RAM is normally volatile, which means that it loses its stored data when the power is off. So, in order to keep the data from being removed, the data is saved in non-volatile memory like hard disk. The data is only retrived from the hard disk when the program is running.
The Fetch-Execute cycle
The Fectch-Execute Cycle is the way the CPU works. The reason it's called Fetch-Execute Cycle is because the instruction is fectched from the main memory and executed by the processor.

First, when a program is loaded to the main memory (RAM). the processor fetches one instruction at a time from the RAM.

Then the processor decodes the instruction for the next step, Execution.

In the executing step, the decoded insturction is passed to the function units of CPU in a sequence of control sinals.

The result of executing the instruction is then written back to the register. This is called writeback.
Cache is a computer component that stores data so that future instructions can be executed faster. The Cache can either reserve information or act as a storage device. If data that is in the Cache is requested (this is known as cache hit) it is simply read then executed, and this is faster, Cache miss is data that has to be fetched from its storage area, and this is slower than cache hit.
Storage is where we store information and files over a long period of time for future uses. It is non-volatile, which means it CAN store information even when the computer system is turned off, unlike the RAM. It is also commonly refered to as 'secondary memory' or 'secondary storage'. Due to the great demand of storage, it is relatively cheap compared to the RAM.
Why Do Computers and Computer Users need storage?
Why do computers and its users need storage?
Simply, we all need storage so that we can save things such homework on a Word document. If we didn't have storage we couldn't save anything, and everything we downloaded would be deleted as soon as the CPU is turned off. Therefore, we need stprage so that everything we download such as pictures and music, and work we do would be deleted if we did not have storage. This storage is cakked 'secondary storage'. Primary storage is the RAM.
Why do we need Storage?
What types of Storage is there?

What types of storage is there?

Magnetic storage
This is the oldest type of storage, these are things such as floppy disks, hard disks and tapes. These are read by a moving head with the disks, however the tape is read by moving the tape past a 'read-write' head.

These are things such as a CD disc, and data is read from it through laser technology.

Flash Storage
These are the newest storage, called flash memory, and this erased and reprogrammed through electronics. These are also called 'solid state' memory, and they have no moving parts. Therefore it is cheaper, smaller and has a lesser possiblility for something to go wrong. These can be USB sticks, or memory cards in phones and cameras.
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