Your system has three basic types of software: application programs, device drivers, and operating systems. Each type of software performs a completely different job, but all three work closely together to perform useful work. While some special-purpose programs do not fit neatly into any of these classes, most software does. Programs run in the memory portion of the system. While running, programs are known as processes or jobs. The following illustration shows the relationship between the different software programs and the hardware.
Application programs are the top software layer. You can perform specific tasks with these programs, such as using a word processor for writing, a spreadsheet for accounting, or a computer-aided design program for drawing. The other two layers, device drivers and the operating system, play important support roles. Your system might run one application program at a time, or it might run many simultaneously.
Device drivers are a set of highly specialized programs. Device drivers help application programs and the operating system do their tasks. Device drivers (in particular, adapters), do not interact with you. They interact directly with computer hardware elements and shield the application programs from the hardware specifics of computers.
An operating system is a collection of programs that controls the running of programs and organizes the resources of a computer system. These resources are the hardware components of the system, such as keyboards, printers, monitors, and disk drives. Your AIX operating system comes with programs, called commands or utilities, that maintain your files, send and receive messages, provide miscellaneous information about your system, and so on.
An application program relies on the operating system to perform many detailed tasks associated with the internal workings of the computer. The operating system also accepts commands directly from you to manage files and security. There are many extensions to the AIX operating system that allow you to customize your environment.
Root-user processes are programs that can be run only by a user with root authority. A system administrator has root authority for all processes.
Root-user processes include:
When you are not allowed to run a command, the system displays a message saying you do not have the correct permissions or you are not allowed to run that command. The system administrator may be the only person who can log in as root on your system. The system administrator can also set you up to use particular commands, giving you some control over processes.
Note: This guide assumes that the system is already set up and that you are ready to begin using it but without root-user authority. Speak with your system administrator for more information.