Datasheet

❑ Flexibility: You can’t anticipate exactly how ingeniously users will use your program. Try to be

as flexible as possible in your programming. Try to avoid arbitrary limits on field sizes or num-

ber of records. If you can, write the program so that it’s network-aware and able to run across a

network as well as on a local machine. Never assume that you know everything that the user

might want to do.

What Is Linux?

As you may already know, Linux is a freely distributed implementation of a UNIX-like kernel, the low-

level core of an operating system. Because Linux takes the UNIX system as its inspiration, Linux and

UNIX programs are very similar. In fact, almost all programs written for UNIX can be compiled and run

on Linux. Also, some commercial applications sold for commercial versions of UNIX can run unchanged

in binary form on Linux systems.

Linux was developed by Linus Torvalds at the University of Helsinki, with the help of UNIX program-

mers from across the Internet. It began as a hobby inspired by Andy Tanenbaum’s Minix, a small UNIX-

like system, but has grown to become a complete system in its own right. The intention is that the Linux

kernel will not incorporate proprietary code but will contain nothing but freely distributable code.

Versions of Linux are now available for a wide variety of computer systems using many different types

of CPUs, including PCs based on 32-bit and 64-bit Intel x86 and compatible processors; workstations and

servers using Sun SPARC, IBM PowerPC, AMD Opteron, and Intel Itanium; and even some handheld

PDAs and Sony’s Playstations 2 and 3. If it’s got a processor, someone somewhere is trying to get Linux

running on it!

The GNU Project and the Free Software Foundation

Linux owes its existence to the cooperative efforts of a large number of people. The operating system kernel

itself forms only a small part of a usable development system. Commercial UNIX systems traditionally come

bundled with applications that provide system services and tools. For Linux systems, these additional pro-

grams have been written by many different programmers and have been freely contributed.

The Linux community (together with others) supports the concept of free software, that is, software that

is free from restrictions, subject to the GNU General Public License (the name GNU stands for the recur-

sive GNU’s Not Unix). Although there may be a cost involved in obtaining the software, it can thereafter

be used in any way desired and is usually distributed in source form.

The Free Software Foundation was set up by Richard Stallman, the author of GNU Emacs, one of the

best-known text editors for UNIX and other systems. Stallman is a pioneer of the free software concept

and started the GNU Project, an attempt to create an operating system and development environment

that would be compatible with UNIX, but not suffer the restrictions of the proprietary UNIX name and

source code. GNU may one day turn out to be very different from UNIX in the way it handles the hard-

ware and manages running programs, but it will still support UNIX-style applications.

The GNU Project has already provided the software community with many applications that closely mimic

those found on UNIX systems. All these programs, so-called GNU software, are distributed under the terms

of the GNU General Public License (GPL); you can find a copy of the license at

http://www.gnu.org. This

license embodies the concept of copyleft (a takeoff on “copyright”). Copyleft is intended to prevent others

from placing restrictions on the use of free software.

Chapter 1: Getting Started

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