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+# Chapter 2: Operating System Structures
+
+* Chapter 2: 2.1 to 2.5
+
+## Operating-System Services
+
+The OS provides an environment for the execution of programs.
+It provides certain services to programs and to the users
+of those programs.
+
+services provided to the user:
+
+* User Interface:
+  * command line interface: text commands and a method for entering them.
+  * batch interface: commands and directives to control those commands are entered into files, and those files are executed.
+  * graphical user interface: a window system with a pointing device to direct I/O.
+* Program execution: Load a program into memory and run that program.
+* I/O operations: a running program may require I/O, which may involve a file or an I/O device.
+* File-system manipulation:
+  * read and write files
+  * create and delete files by name
+  * search for files
+  * list file information
+  * permissions management
+* Communication:
+  * inter process communication
+  * shared memory
+  * message passing
+* Error detection:
+  * CPU/Memory hardware
+  * I/O devices
+  * user programs
+
+services for ensuring efficient operation:
+
+* Resource allocation
+  * CPU scheduling routines
+  * allocate printers, modems, USB storage devices
+* Accounting
+  * keep track of which users use how mucn and what kinds of computer resources
+* Protection and security
+  * control access to information
+  * one process should not be able to interfere with another process.
+  * access to system resources are controlled
+  * authentication
+
+## User Operating-System Interface