Lecture 4:

• Representation of a process in the kernel: PCB
• process state;
• program counter;
• CPU registers;
• CPU scheduling information;
• file descriptor table;
• memory-management information;
• accounting information;
• identification of the blocking events (if the process is blocked);
• Operations on processes
• process creation: fork and exec system calls;
• parent process and child process; tree-structured ancestor-descendent relationships ;
• Example of process creation: when the kernel is booted, first init process is created; init process then fork off many other processes, one being the login daemon; when a user login, the login daemon fork off the xterm and shell processes for the user environment;
• process termination: exit

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• Introduction to Java:
• What is Java: an object-oriented type-safe platform-independent programming language
• Why is Java introduced: World-Wide Web, HyperText Transfer Protocol (HTTP), HyperText Markup Language (HTML), browsers, problems of extending the HTML and modifying the browsers ---> solution: "platform-independent" code for displaying a page
• Requirement on Java: platform-independency, security
• Solution: Java virtual machine (in some sense, a Java virtual machine is also an operating system)
• Security in Java:
• Java virtual machine provides a set of safeguards;
• type-safety and strongly-typed: very piece of data (object) in the program has a type; definition and use of the data (the object) must be consistent (compatible); at compile time, the Java compiler checks for type compatibility, and reports error on forbidden operations;
• A Java example: the sorting program
• see the example in the tutorial;
• Values, Objects and Pointers in Java:
• Can't create a pointer in Java;
• variables can only hold references to objects, or primitive types;
• Parameters are passed by value;