domingo, 13 de septiembre de 2009

Using Unix

Using Unix
Editorial Que Corporation

ISBN 0-88022-519-X

Comprado de oferta en la antigua libreria Herber. El precio de la etiqueta marca 4.970 ptas., pero me costó bastante menos.

Tuve que comprarlo después del año 1.995, pero no mucho después. Seguramente en 1.996. El libro es del año 1.990.

Un buen libro tanto para administrar la shell, como para programarla, como unos buenos capítulos poniendo en antecedentes. Incluso explica el origen del termino "booting".

Tiene por ej. un capitulo todavía interesante ''A Brief History of UNIX'', información sobre hardware (para que sirve la RAM y la relacion con la CPU, perifericos, ...), un capitulo
"understanding Unix" que suele faltar en los libros demasiado prácticos, una buena explicación de lo que es la swap, como se gestiona la información en los discos... y una buena referencia de comandos bien explicados. Apendices realmente utiles como agrupación de comandos por utilidad, o resumenes de uso de VI, Understanding UUCP, como funcionan los disco (cabezales, sectores), como funciona los inodos y el espacio en disco, un capitulo dedicado a VI, referencia de comandos de shell...

Todo esto explicado sin meterse en detalles tecnicos y de forma que lo pueda entender todo el mundo.

Como curiosidad, tenia ejemplos para AIX PS/2 versión 1.1, y de SCO System v/386.

Unix was developed by programmers at Bell Laboratories in Murray Hill, New Jersey in 1969. By today's standards, you can consider UNIX a fairly old operating system. Of course, UNIX has evolved since 1969. In fact, there i much effort in the Unix community to incorporate the latest desirable features into UNIX. Still, the core of UNIX has remained stable all these years.

You might imagine that such an enduring O.S. originated as being the ceter of attention of a large group o computer specialists. You could picture the debut of UNIX as a full-scale media event complete with a four-color magazine campaign. But like men "legends" UNIX was born in quiet obscurity. UNIX was not developed by a huge team of programmers working with the ultimate specifications of the day. Rather, UNIX was developed by a handful of people, working under the guidance of a programmer named Ken Thompson.

The original UNIX ran on a single type of minicomputer, Digital Equipmen Corporation' (DEC) PDP-7.
[...]
By 1973, most people who used UNIX considered it to be a viable product.
[...]
During its first year, UNIX was not a commercial product. Because the business of AT&T was telecommunications rather than computer-related products, Bell Labs and AT&T were restricted as to what commercial products they could offer. Despite these external limitations, UNIX continued to flourish within Bell Labs.

In 1974, UNIX was licensed to universties for use in education. ATT also made UNIX available to research labs.

Berkley Software Distribution

As you recall, AT&T licensed UNIX to universities during the period when ATT complied with restrictions that kept UNIX from being a commercial product. The University of California at Berkely moved Version 7 to a new supermini computer at the university. The resulting enhanced UNIX was called 3 BSD. BSD is an acronym for Berkeley Software Distribution. BSD, sometimes called Berkeley UNIX, has evolved along its own path since 1979. In 1981, 4.1 BSD was produced at Berkeley, followed by 4.2 BSD in 1984.
[...]
Vendors such as Sun Microsystems have based their forms on UNIX on BSD. Sun's Sun OS is the name of a BSD-derived operating system. BSD is a fine example of how the academic community can contribute to the computer industry in a tangible way.


In the "olden" days of computing (that is until the 1970s) computers used a type of memory called core plane memory. Core-plane memory - also called simply core - is made of thousand of tiny doughnut-shaped rings, each of which is magnetized as a binary 1 or 0.

El capitulo introductorio tenía una buena explicación de las que ya no se ven para comprender como funcina un ordenador. Explica incluso algo sobre el binario, empezando comparandolo con los letreros luminosos de puntos encendidos y apagados, y acabando con algo de aritmetica binaria. Finalmente, lo liga todo explicando que la CPU recibe los comandos con instrucciones en binario, pero que los diferentes fabricantes tienen sus propias especificiaciones sobre como deben construirse los comandos.

Más adelante sigue con un buena explicación de lo que es la memoria RAM, system memory que le llama.

To mak more efficient the CPU's accesing of binary data, each address in RAM is able to store eight or more binary digits or bits. The number of bits stored at each RAM address is almost always some multiple of eight

The grouping of eight binary digits is so common in computing that eight associated bits have their own term. A byte is eight binary digits. 

También explica como funcionan los Kbtyes y los Mbytes. Luego ya se adentra en cosas como el data bus y el address bus. Todo esto que hoy en día parecería tan complejo, explicado a un nivel de usuario.

Tales of Goha


Tales of Goha
Lelie Caplan

Heinemann Guide Readers
ISBN 0-435-27008-7
Intermediate Level

Nueve pequeños cuentos para usarlo como lectura en el curso de inglés de segundo de BUP.