Computer Organization - Binary Representation PDF

Summary

This document covers fundamental concepts in computer organization, including binary representation, interrupts, and other key operating system functions. It also discusses the concept of virtual machines and Voice over IP.

Full Transcript

Computer organization – Binary representation 2.1.9 Bit, byte, binary, decimal and hexadecimal - All data and instructions stored in a computer system are stored in sequences of binary digits that can take only two possible values, 1 and 0. -...

Computer organization – Binary representation 2.1.9 Bit, byte, binary, decimal and hexadecimal - All data and instructions stored in a computer system are stored in sequences of binary digits that can take only two possible values, 1 and 0. - Thus a binary digit (bit) is the basic unit of information in computer systems and can have only two values: either 1 or 0. Eight bits form a byte. > - 1 Byte = 8 bits - A bit is denoted by the small letter b, whereas a byte is denoted by the capital letter B. Thus, 1B = 8b. One byte can store a single character (ex. The letter A). - They are used to denote file sizes stored on memory or disk (ex. a 12MB file) or even connection speeds (ex. 50Mbps). 6. INTERRUPT = allows the current job of a CPU to be suspended temporarily to perform a higher-priority task = signal to the CPU sent by hardware or sotware. Examples o Used to indicate that a client wants access to the server (in a mul\ access system) o A peripheral needs serving (printer) o Sotware applica\on reports an error o Power problem alert (low basery) How the CPU handles the interrupt o Interrupt signal is sent to the computer o CPU ac\vates the event handler and suspends/ puts on task the current tasks o CPU services the tasks related to the request of interrupt o When these finish, CPU resumes suspended tasks/ pops them from stack INTERRUPT REGISTER (IR) It is used to detect the posi\on in memory of the specific interrupt-handling code POLLING = a technique which allows one unit to check the status of another unit at regular intervals Can be efficient use of CPU \me Can be used when CPU is not busy HANDSHAKING = the exchange of signals/ messages when the connec\on is established between two devices to establish that the devices are ready to exchange data The sender sends a request for communica\on on a channel to the receiver Receiver replies with parameters/ protocol/ cer\ficate ready to accept The sender verifies cer\ficate and uses the given parameters for the transmission data temporarily - holds BUFFER Peripheral devices are oten slow whereas CPU is fast CPU fills the buffer so that the device (fax/ printer) can access the data at its own speed, allowing the CPU to work on other tasks PAGING à something like virtual memory - > increase secondary as it was p memory. It is used in the forma\on of virtual memory/ use of secondary memory to increase the amount of primary memory Memory is divided into (tagged) “pages” which are then transferred in and out as required FEATURES TO BE CONSIDERED WHEN COMPARING THE SPEED OF DIFFERENT PROCESSORS Word length Bus size Frequency Number of cores Cache size VIRTUAL MACHINES Provide a sotware emula\on/ virtualiza\on of other opera\ng systems while hiding/ abstrac\ng the physical environment/ O.S/ execu\on environment of the host machine Virtual machines do not directly correspond to any real plazorm so sotware may be tested/ executed on any plazorm (portability) This is more prac\cal/ economical than having to test sotware on several computers with different OS The sotware to be tested is compiled into the language of the virtual machine, and this is interpreted into the language of the host machine VOICE over IP = Audio (and video) stream transmised over internet Broadband internet connec\on needed It can be integrated in an office desktop computer with collabora\on desk endpoints/ webcams/ desktop computer/ widgets/ touch screen/ specific applica\ons/ IP phones Resources required: o Bandwidth § Available bandwidth/ a trade-off between bandwidth and quality of audio-video streaming § Low bandwidth makes streaming disrupted/ discon\nuous and impacts on the quality of the collabora\ve environment § Bandwidth also depends on how many people in the office will use VoIP and their simultaneous opera\ons (uploading/ downloading) o Router § Router should be powerful/ good enough to support all opera\ons related to collabora\ve work § Some specific routers provide quality of service for voice transmission over other func\ons, for example WiFi/ VPN connec\ons § Normal routers do not dis\nguish the internet traffic, and the quality of audio- video streaming may decrease o Network § Quality of internet varies, for example delays/ conges\on are cause of losses/ echoes/ scasered images § Having two separate networks for VoIP and other computer opera\ons may help in some cases (depending on the dimensions and opera\ons of the office), so that the router can handle them separately § For example, somebody talking over the IP is not hindered by somebody else in the same office downloading from the internet o Power § In case of power loss the telephones will also not work § A backup system/ second just for the telephones is necessary FUNCTIONS OF THE OPERATING SYSTEM IN RELATION TO MULTITASKING Memory management o O.S allows more than one program/ process to share the memory by alloca\ng separate memory to each program o It provides memory isola\on for each of processes o The system may begin to run out of shared storage (as many programs are running) so OS moves pages to disk/ paging Processor management o To allow (the appearance of) more than one program running at the same \me by the alloca\on of \me slices o Decides which process runs at a certain point in \me o Arrange the execu\on of applica\ons so that we believe that there are several things happening at once (scheduler) o Priori\zes tasks by importance (interrupts) System resources include: computer hardware, sotware, trained personnel, and suppor\ng infrastructure PRIMARY MEMORY = all processed data and instruc\ons and all resul\ng data have to be stored in primary memory Directly connected to the processor and feeds the processor with the required data by the fetch, wummmmm decode, execute cycle data and instruc\ons RAM AND CACHE MEMORY = all data and instruc\ons held in RAM may be altered at any \me 2 types of RAM: sta\c (SRAM) and dynamic (DRAM) RAM holds data as there is power SRAM (sta\c RAM) - long as = type of semiconductor memory that holds data for as long as there is power supply to the memory circuits More expensive, needs more transistors per byte, faster than DRAM Used in small quan\\es Placed between the processor and the DRAM à directly feeds the processor leaks data gradually DRAM (dynamic RAM) =semiconductor gradually leaks away and needs to be refreshed periodically Used in large quan\\es in primary memory ROM (Read Only Memory) = nonvola\le and slower than RAM Used to hold cri\cal instruc\ons used to start up a PC A common use of ROM is to hold the Basic Input Output System which makes it possible for a PC to boot and some\mes to hold the en\re OS for old small home computers SECONDARY STORAGE = hardware that provides data integrity, low cost, mass storage capacity, and permanent storage 2 broad types of secondary memory devices: direct access and sequen\al access and executed as a group together watched ⑮ In batch processing, some programs are batched together and then executed as a group, without the need of any intervention from the user. Only one program is running at a time, while the others are waiting for their turn. When it completes, the next program in the queue runs, and so on, until all the programs in the batch are run. > 2 or - more loaded in the main memory In multiprogramming, two or more programs may be loaded in the main memory. However, only one program - will be executed by the CPU at any one point in time. All the other programs will be waiting for their turn. The idea behind multiprogramming is to- maximize the use of CPU time (i.e. CPU idle time should be minimized) Multitasking is similar to multiprogramming with the subtle difference-that tasks or processes (instead of whole programs) are performed simultaneously and - share a common resource, for example, one CPU. Each task finishes, before another takes up the CPU, as was the case in multiprogramming. However, tasks are a lot "smaller" than programs and as such are completed very quickly. Both multiprogramming and multitasking operating systems are Central Processing Unit time-sharing systems. - Multiprocessing refers to the hardware and means that a computer system has more than one CPU core. This might mean multiple CPU dies or even multiple cores in one or more CPU dies. Multithreading is the ability of a program or an operating system to- execute different parts of a program, called threads, simultaneously. W => The program has to be designed by the programmer in such a way that all the threads can be executed at the same time without interfering with each other. - Swapping is the general term of a mechanism in which a process or blocks of program code can be -swapped temporarily out of RAM and into a hard disk, and then, later,u continue their execution. brought back into RAM to - Paging is the underlying mechanism of virtual memory implementation, which allows all modern OS to utilize the, much greater in size, secondary storage as if it was RAM. Excessive page swapping causes thrashing that results in poor system performance. Symbian is a mobile OS designed for smartphones TinyOS is a free and open-source, embedded, component-based, OS and platform for low-power wireless devices, such as those used in wireless sensor networks and home automation. Tizen is an OS based on the Linux kernel and the GNU C Library implementing the Linux API. Embedded Configurable Operating System (eCos) is a free and open-source, real-time, OS that was engineered to serve embedded systems and applications which need only one process with multiple m threads. - 7.1.1 A CONTROL SYSTEM g - One or more devices that guide other devices or system - Allows the compeOOon of various tasks in an automaOc manner à without any human interven\on - Set up once – perform the ac\ons that they have been programmed to do in an automa\c manner - May include sensors to gain feedback from the environment and motors to control any actuator in an appropriate manner - Ex. the automa\c doors - The sensor may use infrared or microwave signals that bounce off of objects to determine motion. After receiving feedback from the environment, the sensor forwards its signal to a just microprocessor and allows the control system to operate its actuators to open the doors only when motion is detected. Furthermore, more advanced automatic doors include photocell read sensors that can tell if someone is at the door so that the doors do not close on them. This results in a control system that is very convenient, as well as efficient, when one considers that doors cannot now be left open accidentally, which may be costly when a heating or air- conditioning system is operating.

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