Proccess Creation

Introduction

The UNIX system kernel is the master organizer of UNIX. The kernel schedules processes, allocates memory and disk storage, supervises the transmissions of data between the main storage and the peripheral devices, and honours the processes' requests for service. The traditional UNIX system kernel addresses three major tasks: process management; device management; and file management. These three areas remain central, but dramatic advances in hardware and software have expanded the role of the kernel. Today's kernels usually provide these additional services: virtual memory, networking, and network file systems. Additional kernel features that exist in some versions of UNIX, but that are not universally available include multiprocessor support and

lightweight process support. The purpose of this report is to focus on process creation. This includes starting processes, scheduling processes, swapping processes to disk, allocating resources.

Process

A process is a program that is being executed. For a given program, there may be any number of processes running at a particular time. When we speak of a process, we are talking about something that is active, something that is going through execution. The term process generally refers to activities that are catalogued in the UNIX system kernel's process table. The process is the fundamental unit of organization in the UNIX system. The kernel stores vital information for processes in two places: the process table and the user table. There is a single process table for the entire system. It contains one entry for each process. If you try to start a process when the table is full, the kernel refuses. The process table is referenced during all of the life stages of processes. Creating a process involves initializing an entry in the process table, initializing a user table and loading the actual text and data for the process.

UNIX is a multi-task operating system: many processes may be executed at the same...