This document discusses process synchronization techniques in operating systems. It covers critical sections, Peterson's solution, synchronization hardware using test-and-set instructions, and semaphores. Semaphores provide a synchronization tool that avoids busy waiting. They can be implemented using waiting queues to prevent processes from busy waiting. The document also briefly discusses deadlocks and starvation that can occur with synchronization.
This document discusses forms and global variables in PHP. It covers creating forms using the <form> element and GET and POST methods. It also discusses accessing form data using $_GET and $_POST superglobals. The document explains validating form input to prevent attacks and escaping output with htmlspecialchars(). It introduces global variables in PHP like $GLOBALS and superglobals like $_SERVER that are available everywhere.
The document discusses the physical layer in networking, including defining signals, transmission mediums like cable, DSL, and fiber optics, and multiplexing techniques. It explains the differences between analog and digital signals and data, as well as defining related terms like speed, bandwidth, frequency, and wavelength. The various types of multiplexing including FDM, TDM, and WDM are also described.
This document discusses process synchronization techniques in operating systems. It covers critical sections, Peterson's solution, synchronization hardware using test-and-set instructions, and semaphores. Semaphores provide a synchronization tool that avoids busy waiting. They can be implemented using waiting queues to prevent processes from busy waiting. The document also briefly discusses deadlocks and starvation that can occur with synchronization.
This document discusses forms and global variables in PHP. It covers creating forms using the <form> element and GET and POST methods. It also discusses accessing form data using $_GET and $_POST superglobals. The document explains validating form input to prevent attacks and escaping output with htmlspecialchars(). It introduces global variables in PHP like $GLOBALS and superglobals like $_SERVER that are available everywhere.
The document discusses the physical layer in networking, including defining signals, transmission mediums like cable, DSL, and fiber optics, and multiplexing techniques. It explains the differences between analog and digital signals and data, as well as defining related terms like speed, bandwidth, frequency, and wavelength. The various types of multiplexing including FDM, TDM, and WDM are also described.