- The user clicks on a link to a webpage from a previous webpage.
- The browser resolves the ip address from the server name and sets up a tcp connection to the server (usually on port 80 or 8080)
- The browser sends a http request to the server containing the requested resource and information about itself, e.g browser type, supported language etc
- The server generates a response which contains header information as well as HTML code for the browser to render.
- The browser interprets the code and displays the page to the user.
The url https://www.buythings.com would be preferred since this http protocol includes SSL (Secure sockets layer) or TLS (Transport layer security) which encrypts all HTTP information such that only the sender and the receiver can decipher the information. This is more secure, especially in the case where the http information can be intercepted by malicious entities on the network, they won’t be able to read the sensitive payment information that can be used defraud the online shopper.
A process is a running program.
The PCB stores metadata necessary for managing the process, e.g. process id, process state, memory allocation addresses, scheduling info (priority, time slice), pointers to it’s resources (files, other processes).
Paging is were each process in an OS is allocated memory in units called pages for easier coordination and management by the operating system. The pages can be stored physically in memory , or stored on the hard disk (in the case that the process is not running at that time). If a process is stored on the disk and needs to be run, a page fault is generated so that the process is swapped back into the physical memory for processing.
Thrashing occurs when memory resources become limited by the amount of running processes. The need for physical memory can be exceeded, thus multiple processes that are in waiting state are stored as pages on disk. For continued running of the system, processes are constantly swapped in and out of physical memory, an execution which spends a lot of time on the cpu when compared to running the processes themselves.
- Because of the frequent process swapping by page faults, the system becomes inefficient and can run slowly. (The solution is to inefficiency increase the size of physical memory by upgrading the ram size, or configure/manage the system to run less processes.)
- The system can become overwhelmed to the point of “crashing”, i.e stop working or responding altogether.
Too little physical memory is available for a system that needs to run a lot of processes.
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