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1.1. Introduction All operating systems provide services for programs they run. Typical services include: a. executing a new program, b. opening a file, c. reading a file, d. allocating a region of memory, e. getting the current time of day, and so on. 1.2. UNIX Architecture An operating system can be defined as the software that a. controls the hardware resources of the computer and b. provides an environment under which programs can run. System calls: the interface to the kernel is a layer of software Shell: a special application that provides an interface for running other applications. 1.3. Logging In A shell is a command-line interpreter that reads user input and executes commands. 1.4. Files and Directories Every process has a working directory, sometimes called the current working directory. A process can change its working directory with the chdir function. |
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