ProfitPress Mega CDROM2 Shareware Freeware (MSDOS)(1992)(Eng)

home *** CD-ROM | disk | FTP | other *** search

/ ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng) / ProfitPress-MegaCDROM2.B6I / MAGAZINE / MISC / CNEWS013.ZIP / CNEWS013.NWS < prev next >

Wrap

Text File | 1988-12-28 | 67.6 KB | 1,473 lines

C NEWS Vol. 1 Issue 13 December 27, 1988 *-------------------------------------------------------------* | C NEWS - International C Electronic Newsletter/Journal | | "Dedicated to the Art of C Programming" | | | | Founded 12/27/87 | *-------------------------------------------------------------* Table of Contents The Heap: Messages from the Editor ..........................2 by Barry Lynch Book Review: Software Engineering in C ......................5 by Barry Lynch Magazine Review: Circuit Cellar Ink ..........................7 by Barry Lynch Compression Utilities: One Sysop's View .....................8 by Barry Lynch Commentary: ................................................10 by Arnie Cherdak Program Design: A Utility: OpusGraf ........................12 by Jim Singleton and Barry Lynch AWK: An Introduction Part I ................................16 By Dan Kozak Message Threads from the C BBS: ............................22 by Users of the C BBS - Changing a File Attribute - Chris Kryza - Checking the Size of a Directory - Bob Smith Interactive C Graphics: Part I .............................23 by Scott Houck Article Submission Standards ................................28 Address's ...................................................29 Distribution Points .........................................30 User Response Form ..........................................31 C News is an Electronic Journal published by the C BBS in Burke, VA on a monthly basis. The subject for C News is the C programming language, as well as any derivatives like C++. All readers are encouraged to submit articles, reviews, or comments for submission. C News is freely distributed, but can not be sold for a profit, or cannot have a charge assessed to cover distribution costs. To do so is in direct violation of the License agreement. Copies of which are available from the C BBS. This publication is Copyrighted under U.S Copyright Law. Page 1 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== THE HEAP: Messages from the Editor ===================================================================== TABLE OF CONTENTS: - Status of the C BBS - What's in this issue of C News - User feedback revisited in gentler terms - Postcards wanted - Software Distribution System (SDS) distribution of C News - New feature starting with this issue of C News - What is planned for Year 2 of C News [STATUS OF THE C BBS: OR HOW A HARDISK CRASH MAKES ME FEEL HUMBLE ..] It's been a long couple of weeks here at the C BBS, a catastrophic hardware failure caused the complete loss of the C BBS itself. Luckily, I had most of the C source files on disk and was able to recreate the BBS. Some minor things still need to be completed, but the board is operational and once again C News is being cranked out on an infrequent basis. One thing the crash did was delay this issue of C News by a month or so. Instead of canvassing for articles, I was out drumming up old C BBS C src files and attempting to get my echo and netmail areas to work. No, I did not have a backup, who does when it is 80 floppies!! [WHAT'S IN THIS ISSUE OF CNEWS?] This issue of C News features book and magazine reviews, also in this issue three different multi-part articles are presented: Software Design, Interactive C Graphics, and AWK. We were blessed with three seperate projects at the same time, and this allows us to split the articles apart and have material for a couple of issues of C News. This also allows you the reader the opportunity to provide some feedback to the authors that can be included in a future issue of C News! I hope that you will enjoy these articles as much as we have in bringing them to you. [USER FEEDBACK] Remember back a few issues in this column, I mentioned how little feedback we were receiving? Well in the last month, postcards, letters and electronic mail messages have been arriving from around the globe. For instance today, a user logged in from Ireland and praised the editors and writers of C News for putting C News together. This is the sort of feedback that we have been looking for, nothing makes a volunteer feel better than a nice compliment on his or her efforts. All writers of C News are volunteers and a little feedback is needed. Keep up the good work, and keep those postcards Page 2 C NEWS Vol. 1 Issue 13 December 27, 1988 coming! [POSTCARDS WANTED!] Postcards are still wanted!! To date postcards have been received from Arlington, Virginia, New York, New York, and Montreal, Canada. So the breakdown to date is: United States World Virginia Montreal, Canada New York Maryland [SOFTWARE DISTRIBUTION SYSTEM (SDS) DISTRIBUTION OF CNEWS] C News will begin dsitribution in the Northeast section of the country via SDS with this issue. This is in direct response to a netmail message that I received from the coordinator of SDS for the NE. This is a big step for C News, as it brings it closer to the intended audience. C News was originally intended for the readers of the Fidonet C Echomail conference, but has grown to be an international electronic journal that tranverses networks and systems. Please upload C News wherever you can, and let's spread the word...... [NEW FEATURE STARTING WITH THIS ISSUE OF CNEWS] Following in the foot steps of "Byte" and "Circuit Cellar Ink", I have decided to place message threads of interest to C programmers, from my BBS in this newsletter. This allows users/readers that do not log onto the C BBS, the chance to see a question and the responses that were received. The first message thread was started by Chris Kryza, concerning how to change a file attribute, the second thread deals with some floating point problems during execution of a program in TurboC, and the third is a check directory program. Enjoy these tidbits and if you see somthing that needs correcting or further explanation do not hesitate to ask. [What is Planned for Year 2, of C News?] Well, believe it or not we have almost come full circle. Back last December I started C News out of the frustration of reading the same questions over and over again in the C_Echo. Little did I know, or dare to dream that C News as it is to day would exist. This is not a commercial product nor will it ever be. It is not intended to compete with the multitudes of programming journals and magazines that exist, but compliment them. Let's welcome the new year by giving a hand to the users of the C BBS and readers of C News that have taken the time to contribute!! <clap, clap, clap> Page 3 C NEWS Vol. 1 Issue 13 December 27, 1988 C News Contributors (1988) David Nugent - Melbourne, Australia Marshall Presnell - Parts unknown at the moment David Cheslow - Dallas, Texas Arnie Cherdak - Silver Spring, Maryland Bill Mayne - Silver Spring, Maryland Jim Singleton - Arlington, Virginia Jerry Zeisler - Herndon, Virginia Jack Hess - Dallas, Texas Dan Kozak - Arlington, Virginia and Scott Houck - Washington, D.C. Page 4 C NEWS Vol. 1 Issue 13 December 27, 1988 ====================================================================== BOOK REVIEW: By Barry Lynch ====================================================================== Title: Software Engineering in C Author: Peter A. Darnell Philip E. Margolis ISBN Number: 0-387-96574-2 Publisher: Springer-Verlag New York-Berlin-Heidelberg Back in Issue 10 of C News, I stated in the Book review column: "The last thing I needed - and my checkbook - was to buy another computer book" Well, this is still the case but I can definitely make an exception in with this book. Rarely is it that I can pick up a book, and in a few moments know that the book is worth the cover price. To often in our profession we are forced to pay good money for books that are not worthy of our time. This is not the case with "Software Engineering in C". The title is a tad deceiving, as it seems to indicate that the book is another dry text on software engineering principles, of which a few are on the bookcase to my right. < For sake of brevity I will refer to the book in the remainder of this document as "seC">. seC is an attempt to explain proper software engineering principles using one of the more popular languages on the market today. For instance: In Chapter 12 - Software Engineering, sections are included on: - Product Specification - Software Design - Project Planning Cost Estimation - Software Tools for Software Production - Debugging Techniques - Testing - Performance Analysis - Documentation - Source Control and Organization. All topics that are relevant to the software engineer professional. The authors use a "Useful" application to flesh out the ideas and concepts presented in the book: A C Interpreter. To often in books of this nature, the example application given is a "Mailing List Manager", or a "Graphics Menu System". This is a meaty application for a meaty book. Messer's Darnell and Margolis have done an excellent job in this regard. Is this book for the beginner? The title suggests not, not like "QuickC Programming for the IBM" does. But the authors have attempted to create the seeds of excellent programmers early in the process, instead of just gearing the book to more advanced users. They also cover in some detail the proposed new ANSI standard for C. In one of the appendices included in the book, syntax of ANSI C is outlined. While in a later appendice, the differences between K&R C and ANSI C are outlined. This sort of detail can only add more substance and reason for me to break my budget and purchase a copy. I highly recommend that Page 5 C NEWS Vol. 1 Issue 13 December 27, 1988 you do the same. **** Editor's Note: This book will be used extensively in the series on Product design that starts with this issue. BL Page 6 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== MAGAZINE REVIEW: By barry Lynch ===================================================================== Magazine: Circuit Cellar Ink Issue: Vol 1, No. 5 Publisher: Circuit Cellar Incorporated 4 Park Street Suite 20 Vernon, CT 06066 (203)875-2751 At this time my favorite journal is "Micro Cornucopia". I also favor "C Users Journal" and the "Harvard Business Review". Each month without fail each of these publications is read, re-read and cataloged away for future reference. Today, a new journal threatened to join that select group: Circuit Cellar Ink. For those of us that remember Byte back when, Steve Ciarcia was always one of the shining points of each issue. I can remember back in the early 80's, drooling over a computer that Mr. Ciarcia had put together, and hoping that some day one would find it's way to my door. (This was right before the IBM Pc was introduced I believe) Being very interested in Software and Hardware I find his columns to be of great interest, as he dreams up new wonderful electronic gizmos to build. Sort of reminds me of those wonderful hacker days, before the word became a mark of distrust, instead of pride. This magazine is Mr. Ciarcia's attempt to provide a technical journal that caters to the tinkers, and thinkers that exist in today's computer society. I for one am not interested in how to program a Lotus spreadsheet, but creating a Home control system via a power line interface is more my speed. In the issue that I read today, the lead article was on a project called "ROVER" which stands for "remotely operated video-based electronic reconnaissance". Imagine calling a video camera at home, and watching it pan your yard at your control!! NEAT. If these are the sort of articles that you like, then this little known journal is for you. It is rather new and hard to find on newsstands, but I found my copy in a B. Dalton Software Etc store. If you cannot find it locally, consider calling the publisher to see where it is located locally. Page 7 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== COMMENTARY: File Compression Utilities by Barry Lynch ===================================================================== In the Bulletin Board community, there is one group of utilities that are as indispensable as the modems that the BBS Systems use: the File compression utilities. Two companies have been the leaders in the use of these type of utilities: SEA Associates and Phil Katz Ware. Both of these companies have been involved in a legal dispute over the origin of Phil Katz's code. Needless, to say, due to the fact that almost every DOS based BBS system uses either ARC or PKARC, this legal action has been followed with close scrutiny by most system operators and users alike. This commentary is not on what package to use, but what I have chosen to do here at the C BBS and with C News. Starting with this issue of C News, each issue will be compressed and contained within a library using ZOO. ZOO is another of the File Compression utilities that is currently available, to the sysop and user. It is Public Domain, except for it's restriction on pay per hour BBS systems, and the C source is available. Here at the C BBS the latest version can be found along with utilities to make the transition from ARC type files to ZOO. Why did I decide to go with ZOO? Basically because the entire SEA vs Pkware made me ill. I have absolutely no problem with making a profit off of a product which you create. But the lawsuit that ensued and the bickering that went back and forth between both parties, just made me change to a librarian utility that was not under so much heat. Zoo is public domain as is C News and it fit. Simple, and effective, the "ARC" wars have just begun I am afraid, and what you will see now is a rash of programs that are based upon the essentially the same algorithms, that claim to be faster, better and cheaper. I for one would like to see a NEW data compression algorithm that makes these claims, that would be news. So since I decided to use ZOO, would the file sizes the smaller/bigger than the ARC's that I currently have? Is ZOO faster,slower, or the same speed in compressing files? These are the questions that I will answer in the next paragraph. I chose to use three C source files in a separate sub-directory as my test files. I compressed them all into one file using the following utilities: SEA Assoc. ARC versions 5.2, and 5.32, Phil Katz's PKARC, PAK version 1.0, and ZOO version 2.01. The source files listed with sizes are contained in Table 1.0, and the compression results are listed in Table 1.1. Page 8 C NEWS Vol. 1 Issue 13 December 27, 1988 Table 1.0 - Source files with sizes. SOURCE FILES Editor.c - 21983 Menu.c - 4150 Window.c - 9339 Table 1.1 - Results of Compression Utilities. Program Compression Size of Ratio of each Test.Arc src file. SEA ARC 5.2 Editor.c 67% 13052 Menu.c 47% Window.c 60% SEA ARC 5.32 Editor.c 69% 13052 Menu.c 47% Window.c 54% PAK 1.0 Editor.c 69% 12950 Menu.c 48% Window.c 54% PKARC Editor.c 68% 13007 Menu.c 48% Window.c 59% ZOO 2.01 Editor.c 68% 13423 Menu.c 47% Window.c 54% Page 9 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== COMMENTARY: James L. Buie - TTL Inventor by Arnie Cherdak ===================================================================== I ran across this obituary in an old issue (mid-1988) of one of those electronics industry newspapers that I get at the office. I was browsing idly one day after a tough meeting... *************************************************************** PANORAMA CITY, Calif. - James Buie, who invented and patented transistor-to-transistor (TTL) logic in the early 1960s died here last week at the age of 68. Mr. Buie's invention, TTL, was to become the most widely used form of circuit logic, and was broadly licensed throughout the then-emerging integrated circuit industry by TRW, for which the inventor worked. James L. Buie was born in Hollywood, Calif. in 1920 and educated at Hollywood High School and Los Angeles City College. After World War II, where he rose to the rank of Lieutenant Commander as a naval pilot, he enrolled at the University of Southern California for a bachelor of science degree in electrical engineering. In 1954, Mr. Buie joined the Ramo-Wooldridge Corp., a TRW predecessor company, where he was assigned to Pacific Semiconductor Co. Along with inventing TTL, Mr. Buie was involved in the development of dielectrically isolated integrated circuits, a single-chip parallel multiplier, a single-chip analog-to-digital converter and triple-diffused bi-polar devices. Until 1977, Mr. Buie served as technical leader of TRW's Microelectronics Center, which he helped to establish. He was also instrumental in the startup of the LSI Products Division, where he worked until his retirement in 1983. Mr. Buie is survived by his wife, Ione, a son, John, a daughter, Janet Reasoner, a sister Joan Runsvold, and three great-grandchildren. *********************************************************** Page 10 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== COMMENTARY: James L. Buie - TTL Inventor by Arnie Cherdak ===================================================================== I was virtually dumbstruck when I finished reading this. How could this be, that the man who invented TTL, one of the inventions that made modern digital electronics and computer technology a practical enterprise, died and only got 9 column-inches in the back of a trade journal (name forgotten--my apologies) for his remembrance. I never knew James Buie. I didn't even know he did what he did until I read his obituary. But now I sure know who he was and I, for one, won't forget his contribution. I hope his great-grandchildren will know about and remember him as well because they can have pride in their great-grandfather's accomplishments as an engineer who put an industry to work. ********************************************************** EDITOR'S NOTE: I agreed to publish this article on James Buie because I felt it was important to remember the man that helped to create the hobby or vocation that we all enjoy. BL. *********************************************************** Page 11 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== PROGRAM DESIGN: OpusGraf a Project: Part I: ===================================================================== by Barry Lynch and Jim Singleton Editor's Note: This article is the first in a continuing series on software development. OpusGraf is a opus log utility that creates a bargraph showing utilization for a given day. This graph can then be output to a file to be used as a bulletin. This project will be of interest to all users interested in graphics. [Introduction] The idea for this article came from discussion at one of the C BBS user's meetings that are held every month here in Virginia. The idea of an article that discussed the evolution of a software project, was one that quite a few people showed an interest in. Specifically, Jerry Zeisler in Issue 12 of C News made some interesting observations in his first attempt at a C application. Those observations were the motivation that I needed to sit down and create this project. The other motivation was that when I ran a PC Board Bulletin Board System, a utility was available to show the utilization of the board. And the bulletin that it generated was one of the more popular bulletins on the system. Therefore, this article is the first in a series that will show the development of a utility and outline some of the right things to do, and show some of the things that went wrong. The general plan for content of each article is as follows: Issue Article/Subject 13 Introduction, and Product Specification 14 Detailed Design Document and Flow of Program 15 First BETA release of OpusGraf 16 Bug reports and Corrections 17 Final Release and a Post Mortem Analysis This syllabus allows me to show a complete detailed view of the project, and provide some educational value. I believe that it will also prove to be interesting reader for Fidonet developers and C news readers. SECTION I: The IDEA! How often do you sit at a desk and come up with an idea for a program or great application that we all need? What do you do? Write down your thoughts then and there, or store them away for a later date? I personally carry a Black Composition book - the kind that you find in school bookstores - and make entries as needed. At the end of week, I go through the entries Page 12 C NEWS Vol. 1 Issue 13 December 27, 1988 and make a list of the ones that I want to work on, and a scratch out those that either I have no time for, or was really banana wackers to think of. Once an idea has made it to the "To Do" list, then it is time to think of exactly what it is I am trying to accomplish. This is how OpusGraf started, a brief thought that the OPus sysops needed such a utility, and it would make a good C News series. So, what is it that I want to accomplish? Well, let's see: - A Utility that will read the previous day's opus.log and generate a Bar-Graph showing usage. - The ability to redirect the Bar-Graph to a disk file for showing as a Bulletin. - The option for the sysop to break out the type of utilization to be shown: i.e.: Human Caller/Mail/FR/Maintenance, or All. [Product Specification] Now that the idea is written down and a short but simple list of objectives is written the design work can begin. The first thing to do is to create a rough outline of what you want the program to do. Listed below is a simple outline that can be used as a guideline: - Abstract of project - Command line interface - Input file syntax - Screen design - Output file format descriptions - Interactive command language (If needed) - Error messages - Future extensions Now for a sample product specification for OpusGraf, based upon the outline listed above. 1. Abstract The intent of this project is to create an Fidonet Compatiable graphic utilization utility. It will support: o Opus BBS systems o Fido BBS systems The goal of this project is to show some principles of software engineering and project management while creating a useful Fidonet based Utility. 2. Command Line Interface The command line does not need to include any parameters, unless the user would like to overide some values that exist in the configuration file. Valid command line parameters are: Page 13 C NEWS Vol. 1 Issue 13 December 27, 1988 -A Tells Opusgraf to use all categories of util- ization, i.e.: Human Caller/Machine etc. -F<Path:filename> Path and filename of the configuration file if not the default Opus/Fido/Opusgraf directory. -S Direct output to screen only, no output file is created. 3. Input file syntax File #1: Opus.log The input file will be the Opus.log file created by the OPus BBS system. <I will look for a technical description fof the format in the FTSC documents that outline the technical details of Fido net.> File #2: opusgraf.cfg This is the Opusgraf configuration file that contains certain para- meters needed by the Opusgraf program. The layout is the same that is used by other OPus/Fido utilities, for ease of familiarity and use by the end user. ;*************************************************************** ;* ;* OpusGraf Ver 1.0 Configuration file ;* ;* Written by B. Lynch and J. Singleton of the C BBS 109/713 ;* ;* Purpose: This file is used by Opusgraf.exe to determine what ;* the default operating parameters are. ;* ;* Created for an article in C News Issue's 13-17 (12/88-5/89) ;* ;* LOG c:\opus\opus.log /* The actual opus or fido log to be used */ ALL /* accumulate all utilization into hourly calculations */ ;NOTALL /* break out the different utilizations by hr by % */ BOARD The C BBS /* Your board name */ SYSOP Barry Lynch /* Your name */ ;LOGO "The Home of C BBS" /* Logo or motto of your board */ ; 4. Interactive Command Language Not needed in this application. 5. Error Messages The Opusgraf program supports the following error codes: 1 - No OpusGraf.cfg file found 2 - Log file not found - as specified by config file 3 - Not enough memory to run utility Page 14 C NEWS Vol. 1 Issue 13 December 27, 1988 4 - Unable to write out disk file - Not enough Free disk space 5 - Incorrect command line values <show help screen> Once you have completed the rudimentary design, a detailed design document is needed to outline the algorthims used, libraries, compiler etc. We will save that document for the next issue of C News. Page 15 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== An Introduction to AWK by Dan Kozak ===================================================================== Why AWK? Every programmer spends more time than they will admit doing rather mundane tasks. First you hear a rhythmic clicking from their keyboard, going faster than any programmer could possibly type unless it was a totally repetitive job. "What are you doing?" "Ummm, well I found a much better way to lay out these data files, but I have to go in and indent like so, put a tab here and two newlines as a delimiter and then . . ." Sound familiar? You find yourself doing all kinds of data formatting manually that you should really get the computer to do for you because it's just too much bother to write a program to do it and anyway, you only have to do it once (sure). AWK is great for quick data transformations, validations, reports and also for prototyping larger programs. You may find that knowing AWK will make jobs like this so simple that the equation tips in favor of ACTUALLY WRITING A PROGRAM TO DO THE JOB FOR YOU! (Remember: computers are supposed to make life easier.) [What is AWK?] AWK is an interpretive programming language that was developed by Alfred Aho, Peter Weinberger and Brian Kernighan (put the first letters of their last names together . . . ) at Bell Labs. Although originally designed for short, one-time use programs, it has been extended to handle more complex jobs, making it more of a complete language. Because of its interpretive nature and the way some of its constructs work, it is not especially fast, but when development time is more important than run-time (i.e. you don't use the program all the time) and the amount of data isn't overwhelming AWK's performance is fine. Although it's origin as a UNIX tool is shown in it's use of regular expressions and a C-like syntax, it is applicable to other operating systems as well; in particular there are implementations under MS-DOS (without which I wouldn't be writing this). [How does AWK work?] In AWK, much of the work of writing a program is done for you by the structure of the language. Each program consists of a series of patterns and actions, the input file(s) are read in and every time a pattern is matched the corresponding actions is taken. An AWK program is an implicit loop that, in pseudo code looks like this: (optionally do something here before we start) while (not end of input file(s) ) Page 16 C NEWS Vol. 1 Issue 13 December 27, 1988 if (there is a pattern match) take the coresponding action (optionally do something here when we're done) [What are patterns?] A pattern is a way of specifying "this line of input belongs in set A and that line does not". When you apply a pattern to a line of input the result is a logical value (TRUE/FALSE) that determines whether the coresponding action should be taken. One kind of pattern is the regular expression, a notation for describing a pattern to match that is used throughout UNIX (MS-DOS users: "wildcarding" of filenames is a very small subset of UNIX regular expressions). A regular expression is usually delimited by slashes ("/") and specifys, using both normal characters and "meta-characters" a pattern to look for. So a simple AWK program might look like this: /UNIX/ { print } ^ ^ | +--action pattern This would print every line in the input file that had the pattern "UNIX" in it. Actually the default action (we'll get to those soon) is print so this example could be written at the command line level like this: awk "/UNIX/" input.fil (for the rest of this article, though, I will continue put the superfluous { print } because it reads clearer.) The default, outer level pattern is "match all lines" so this: { print } would simply print all lines. Patterns can be compound like this: /UNIX|AWK/ { print } # the | symbol is a logical OR The complete syntax of regular expressions is more than we can go into here, but there is ample UNIX literature on the subject. Patterns don't have to be regular expressions, they can be any kind of expression. AWK automatically performs field splitting on the input lines (the default delimiter is "white space" [space, tab, newline] but can be changed). NF is a built-in AWK variable that is the number of fields in the input line. This AWK program: NF < 10 { print } will print all input lines that have less that 10 fields. Field splitting also gives you access to the indivdual fields in an input line via the $0, $1, $2, . . ., $n variables. $0 Page 17 C NEWS Vol. 1 Issue 13 December 27, 1988 represents the entire input line, while $1 represents the first field, $2 the second, and so on. As an example: $1 == "AWK" { print } would print all lines whose first field is the word AWK. Of course more complex patterns can be fashioned using the AWK's logical operators ||, &&, and so on (these perform the same functions they do in C). [What are actions?] Actions are the part of AWK that most closely resemble other programming languages, in particular C. Actions consist of function calls, assignments and conditionals. We've already seen the print function at work, but let's look at another output function, one that should be familiar to C programmers. { printf("%3d: %s\n",NR, $0) } (the built-in variable NR is the number of records read) This example would print the input file with every line preceded by its line number. Assignments also work like C, except that variables need not be declared and have an initial numeric value of 0 and an initial string value of "" (the empty string). Here's a quick word count program: { words += NF chars += length($0) + 2 # DOS uses a CR-LF combination } END { print "Characters:",chars,"Words:",words,"Lines:",NR } Here we've introduced variables (except for the fact that all variables in AWK have both a string and a numeric representation that are used according to context, there's not much say about these, you just use them), assignments, the length function (one of several built-in functions), the comment character (#) and the END pattern. The BEGIN and END patterns are matched when the program starts, before any input has been read and after all input has been read, respectively. By making assignments to the field variables ($1, $2 . . .), you can replace or create those fields: { $(NF+1) = "!EOL!" print } This program adds the string "!EOL!" the end of every line and then prints it. Just to give you a feel for the kind of things actions can do, AWK provides 14 built-in variables (we've seen NF and NR already) that give access to the command line arguments, the filename of the current input file, the field and record separators for input and output and the default format for numbers, 9 built-in math functions including random numbers, 12 built-in string functions (we've used length()) that provide a Page 18 C NEWS Vol. 1 Issue 13 December 27, 1988 variety of search and replace functions and all the control flow statements that exist in C (if, while, for do . . . while, break, continue) except for switch. While space prohibits us from looking at all of these, you should be able to see that AWK provides a wide range of tools. [Associative Arrays] The way AWK handles arrays is different enough to merit its own discussion. Arrays in AWK are one dimensional (although there is a feature to simulate two dimensional arrays, we won't go into that here), can hold numbers or strings and need not be declared. However, AWK arrays are subscripted by strings not by integers (this gives them some of the capabilities of SNOBOL4's "associative memory" and that's why they are called associative arrays). The best way to understand this is an example from "The AWK Programming Language": /Asia/ { pop["Asia"] += $3 } /Europe/ { pop["Europe"] += $3 } END { print "Asian population is", pop["Asia"], "million." print "European populations is",pop["Europe"], "million" } When provided with test data containing a country, it's area in thousands of square miles, it's population in millions and the continent it is in formatted like this: USSR 8649 275 Asia Canada 3852 25 North America China 3705 1032 Asia USA 3615 237 North America Brazil 3286 134 South America India 1267 746 Asia Mexico 762 78 North America France 211 55 Europe Japan 144 120 Asia Germany 96 61 Europe England 94 56 Europe this program produces the output: Asian population is 2173 million. European populations is 172 million There are also some special constructs for use with arrays like the "in" operator, used to determine whether a particular subscript exists in an array, "for (var in array)" which will loop through all the subscripts in an array, "delete" to remove an element from an array and "split()", to divide a string up and place it's fields in an array. Array operations are powerful in AWK, but sometimes hard to understand, so refer to "The AWK Programming Language" for the details (something you'll probably have to do more than once :-). Page 19 C NEWS Vol. 1 Issue 13 December 27, 1988 [Just the tip of the iceberg!] There's more to AWK than I could go into here: user defined functions, more complex output statements, reading from files other than those specifed as input (allows you to interleave two files to produce a report, for example), calls to the operating system through the system() function (works like C), among others. But, you can . . . [Do it yourself] Getting started with AWK is easy. There is a freeware version by Rob Duff that is available with source from his BBS (604-251-1816) which was used in the preparation of this article. Try the programs in the article (the article itself makes a good test input file) to see how you like it. If you want to go further, the required reading is "The AWK Programming Language" by Aho, Kernighan and Weinberger, Addison-Wesley, ISBN #0-201-7981-X which serves as a manual and tutorial for the language. There are also several commercial DOS implementations of AWK, most notably Mortice Kerns Systems' and Polytron's PolyAWK. [An example] In closing I leave you with an example I whipped up in response to a question on the FidoNet C echo. This program counts the lines of code in C program(s) excluding comments. It reports the total number of lines in each file and all together with and without preprocessor directives. The FILENAME built in variable is the name of the current input file and the ~ and !~ operators are the "match" and "no match" operators for specifying regular expressions within a program. The regular expressions here are rather dense because C's comment delimiter "/* . . . */" shares a character with AWK regular expression delimiter "/", so every occurence of "/" within a regular expression must be quoted with the "\" character. But even with that complication, this program was up and running in about 20 minutes. Page 20 C NEWS Vol. 1 Issue 13 December 27, 1988 # count lines in a C program, not counting comments or form feeds # does separate count of preprocessor directives # if a preprocessor directive is commented out, it does not count { if (file == "") file = FILENAME if (file != FILENAME) { printf("Number of lines in %s is: %d\n",file,nl+ppd) printf("Number of preprocessor directives is: %d\n",ppd) printf("Number of lines excluding preprocessor directives is: \ %d\n\n",nl) file = FILENAME tnl += nl tppd += ppd nl = 0 ppd = 0 } # don't count blank lines if ($0 == "") { ; } # don't count lines that are all comment else if ($1 ~ /^\/\*/ && $NF ~ /\*\/$/) { ; } # flag beginning of multi-line comment else if ($0 ~ /\/\*/ && $0 !~ /\*\//) { in_comment = 1 } # flag end of multi-line comment else if ($0 !~ /\/\*/ && $0 ~ /\*\//) { in_comment = 0 } # don't count while in comment else if (in_comment) { ; } # count preprocessor directives separately else if ($1 ~ /^#/) { ppd++ } # count everything else else nl++ } END { printf("Number of lines in %s is: %d\n",file,nl+ppd) printf("Number of preprocessor directives is: %d\n",ppd) printf("Number of lines excluding preprocessor directives is: %d\n\n",nl) file = FILENAME tnl += nl tppd += ppd printf("Total number of lines is: %d\n",tnl+tppd) printf("Number of preprocessor directives is: %d\n",tppd) printf("Number of lines excluding preprocessor directives is: %d\n",tnl) } Page 21 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== CHANGING A FILE ATTRIBUTE IN C: by Chris Kryza ===================================================================== ABSTRACT: Back in early November, Chris wanted to know how to change a files attribute in DOS. Two solutions were presented: 1) use the ATTRIB command, and the 2) Use the _chmod function in TurboC. This article outlines a program that Chris wrote to accomplish the latter. INTRODUCTION From: Chris Kryza Rec'd To: Bill Mayne Msg #44, 04-Nov-88 08:16EST Subject: Archive Bit Bill, thanks for you info re the attrib command. It is one of those DOS commands that I long ago forgot about. After doing a little research, I found a way to accomplish the same thing from within a Turbo C program using the _chmod function defined in io.h. This func takes three arguments: filename (char *), get or set flag (int 0 or 1), and mask (to set archive bit: 0x20, to clear same 0x00). You can also set or clear all other file attributes via this function, i.e. hidden file, system file, read-only, etc. Thanks for putting me on the right track! CDK. *** There is a reply. See #51. From: Bill Mayne Rec'd To: Chris Kryza Msg #51, 06-Nov-88 18:12EST Subject: Re: Archive Bit Glad you solved your problem with the archive bit. Obviously both the attrib command and the function you mentioned are just different ways to call the same DOS interrupt. It is amazing that MS doesn't provide commands to use some other useful interrupts, like renaming a file into a different directory. Fortunately almost all C compilers provide a fairly simple function to call any interrupt you want, though it is nice as in this case to have a more specific function for what you want so you don't have to worry about the registers yourself. *** This is a reply to #44. Page 22 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== Interactive C Graphics using TurboC by Scott Houck. Part I ===================================================================== I recently completed a college course in interactive computer graphics. Most of the students were doing their projects on Macintosh computers. Since I have an AT clone with an EGA at home, I got permission to use my home computer for my projects. I had just gotten Turbo C 2.0, so this was a good opportunity to acquaint myself with Turbo's graphics package. In this installment of C News, I will present some basic graphics concepts and show how to use Turbo C to implement simple geometric transformations. The programs require a mouse and either an EGA or VGA graphics adapter. I am writing this article not as a graphics or C expert, but as an intermediate C programmer who is learning about graphics and in particular, Turbo C's graphics package. There are no doubt many insights that others could provide, and I welcome any comments or advice. [MOUSE PROGRAMMING] ----------------- I have a Microsoft mouse, and I used the Microsoft Mouse programming guide for information on programming the mouse. I have not looked into other types of mice, but I do know that my program does not work correctly with the Logitech mouse. I assume the Logitech mouse must be programmed differently. The Microsoft mouse uses interrupt 33h. Each function is numbered and specified by placing the function number in the AX register. Other registers are used to specify function parameters, if any. I used the int86() function to interface to the CPU registers. I experimented with Turbo's pseudo variables before using int86(), but got some surprising results in the MouseStatus() function since registers containing return values were being overwritten before the function returned. Be very careful with pseudo variables! I could not figure out what was happening until I generated an assembly language listing. All mouse functions in the program begin with "Mouse" as a prefix. Here is a summary of the mouse functions I created: MouseReset -- Resets the mouse to its defaults, tells you whether the mouse hardware and software are installed or not, and also returns the number of buttons in the mouse MouseOn -- Shows the mouse cursor MouseOff -- Hides the mouse cursor MouseStatus -- Returns the state of the left and right buttons and the horizontal and vertical coordinates of the cursor Page 23 C NEWS Vol. 1 Issue 13 December 27, 1988 MouseWaitForPress -- A high level routine that loops until the user presses a button MouseWaitForRelease -- A high level routine that loops until the user releases a button MouseSetHorizPos -- Sets the minimum and maximum horizontal cursor coordinates on the screen MouseSetVertPos -- Sets the minimum and maximum vertical cursor coordinates on the screen MouseRestrict -- A high level routine that restricts the cursor to the viewport MouseFree -- A high level routine that frees the cursor to move about the entire screen [DEFINITION OF THE PROJECT] ------------------------- The program I am presenting allows you to manipulate two types of objects (a triangle and a square) on the screen. You can create an object, delete an object, move an object, delete all objects, print the objects' data structure in a file called PROJ1.DAT, cancel an operation, and quit the program. The objects are placed in a room. The "room" is square, 15 feet on each side. The square is one foot on each side, and the triangle is also one foot on each side. [SOME BASIC GRAPHICS THEORY] -------------------------- This program demonstrates basic geometric transformations -- translation, scaling, and rotation. To understand the program, some knowledge of graphics theory is needed. I will not give exhaustive explanations here, but a general overview is in order. Matrices are used in the program, so it is assumed that the reader has some familiarity with manipulating matrices. The "room" is a "window" from the "world" that we are trying to display on the screen. The room is square, 15 feet on each side. Those are its world coordinates. The term "window" has taken on several different meanings over the years. In standard graphics terminology, however, a "window" is a usually rectangular area that is a subset of your "world". In this case, the window is the 15 foot square area in our world coordinate system. We must transform the window to an area on the graphics screen -- either the entire screen or a rectangular area of the screen. This screen area is referred to as a viewport. When we manipulate objects on screen, we must take the mouse coordinates (physical device coordinates -- 640x350 on EGA, 640x480 on VGA) and transform them into world coordinates. All changes to data about the objects are stored in world Page 24 C NEWS Vol. 1 Issue 13 December 27, 1988 coordinates, which are floating point numbers. Screen coordinates are always integers. [TRANSLATION] ----------- One of the basic graphics operations is translation, that is, moving an object. To translate a point with coordinates (x, y) by an amount Dx in the x direction and Dy in the y direction, add the translation amount to each coordinate: (x+Dx, y+Dy). In matrix notation, if p = [x y], p' = [x' y'], and T = [Dx Dy], then p' = p + T. When translating an object, each point of the object must be translated. For the triangle and square, each vertex will be translated and the object will be redrawn from the translated vertices. [SCALING] ------- Scaling means to change the size of an object. Scaling is done in the x direction and the y direction. The scale factor does not need to be the same for both directions. Scaling is always done about the origin of the coordinate system. For example, if you are reducing an object, not only will the lines become smaller, but they will get closer to the origin. Which brings us to snag #1. All this neat theory I learned in graphics class was for a coordinate system in which the origin (0, 0) is located in the bottom left corner of the screen. However, PC graphics always seem to place the origin in the upper left corner of the screen, so I often had to adjust formulas to work with the PC. To scale a point, multiply the x coordinate by the scale factor for the x direction, and the y coordinate by the scale factor for the y direction: x' = x * Sx, y' = y * Sy. In matrix notation, if p = [x y] and | Sx 0 | S = | 0 Sy |, then p' = p * S. [ROTATION] -------- To rotate a point about the origin by an angle theta, the formulas are: x' = x * cos(theta) - y * sin(theta), and y' = x * sin(theta) + y * cos(theta). In matrix notation, if p = [x y] | cos(theta) sin(theta) | and R = | -sin(theta) cos(theta) |, then p' = p * R. Rotation is always about the origin. To get an object to rotate about its center, you must translate the center to the origin, rotate, then translate it back to its original position. If you do not translate the object to the origin first, the object will rotate as if travelling along a circle with its center at the origin. Page 25 C NEWS Vol. 1 Issue 13 December 27, 1988 [HOMOGENEOUS COORDINATES] ----------------------- Matrices are nice to work with in calculations, but they are even more convenient if the coordinates are homogeneous (expressed similarly). Then matrices may be combined to express composition. For example, a translation followed by a scaling followed by another translation can be done by multiplying the respective matrices together and applying the product to the point in question. Two-dimensional homogeneous coordinates are expressed as 3D matrices, where the last dimension is usually 1 (thought of as a plane parallel to the x-y axis, the w=1 plane). So p(x, y, w), w<>0, is the point in 3D. The 2D projection is (x/w, y/w). If w=1, there is no need to divide, so the 2D point is just the first two coordinates. Again, I will not go into any more theory on this, but there is more explanation in the comments of the code. See the functions Translate(), Rotate(), and CalcW2Vmatrix() for more explanation. By the way, calculating the window to viewport matrix brings us to snag #2: when you use Turbo C's setviewport() function, the upper lefthand corner is changed from its normal screen coordinates to a logical coordinate of (0, 0). While I am sure this simplifies many types of operations, it changes these matrix calculations a bit. [OPERATION OF THE PROGRAM] ------------------------ The user must first place at least one object in the room. This is done by choosing the CREATE button with the left mouse button, then clicking on the triangle or square, and finally choosing a location in the room and clicking with the mouse button to place the object. Deleting an object is done by choosing DELETE, then clicking on the object in the room to be deleted. MOVE is done by clicking on MOVE, then "dragging" the object with the left button depressed, then releasing the button. Rotating is performed by choosing ROTATE, then clicking on an object to be rotated, then clicking or holding down either the left or right button (rotates counterclockwise or clockwise), then choosing QUIT when done. DELETE ALL asks for confirmation through a dialog box. PRINT DATA creates a file called PROJ1.DAT that contains all the vertices of all objects in the room. CANCEL can be chosen to cancel any operation. Choose QUIT to end the program. Human factors were taken into consideration when writing this program. At all times, a message box is shown at the bottom of the screen to guide the user during program operation and to display error messages. The dialog box asks for confirmation. The dialog box is a good example of Turbo's getimage() and putimage() functions. All object information is stored in a linked list. When a user creates a new object, it is placed at the end of the list. When an object is deleted, it is also deleted from the list. Finally, take note of how pick correlation is performed. Page 26 C NEWS Vol. 1 Issue 13 December 27, 1988 Pick correlation refers to associating a mouse button click to an object or an area on the screen. Each area has an "extent" or rectangular boundary associated with it. When the user clicks on the CREATE button, the program must determine which button has been chosen and take appropriate action. Note that choosing an overlapping object in the room will return only the object on the top. More extensive programming would be required to resolve ambiguous clicks. [IN CLOSING] I believe this program will give you a good feel for some basic graphics techniques and Turbo C's implementation. Next month I will present a simple paint program that will demonstrate pull- down menus, "rubber banding" techniques, fill patterns, and mouse cursor programming. Page 27 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== ARTICLE SUBMISSION STANDARDS AND ADDRESSES ===================================================================== As I have repeatedly stated in this newsletter and previous issues, I would like to see user-submitted articles, reviews or questions. Listed below are the standards that should be followed to make my job easier as an editor. - Articles should be submitted in a ASCII non-formatted file. (Margins 0-65 PLEASE) - If the article include code fragments as examples. Then you can include the entire source file if you like for inclusion with the newsletter. - Book or magazine reviews should follow the same format, that is outlined in this issue. The publisher, author, title, and ISBN number are a must. - Compiler/and or product reviews, should include the version number and manufacture. If possible, reviews should include a sample program with benchmarks. If you have any questions you can contact me at the address's included on the next page. Page 28 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== HOW YOU CAN REACH THE AUTHORS OF C NEWS ===================================================================== ADDRESSES The C BBS is located at: C BBS % BCL Limited P.O. Box 9162 McLean VA, 22102 or you can send netmail to: 1:109/713 or MCI Mail to: BCL Limited Page 29 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== DISTRIBUTION POINTS ===================================================================== Board Name Number Net/Node Sysop *** UNITED STATES *** C BBS (703) 644-6478 1:109/713 Barry Lynch McLean, VA Eastern C Board (201) 247-6748 1:107/335 Todd Lehr Exec-PC (414) 964-5160 .. Bob Mahoney Milwaukee, WI TAMIAMI (813) 793-2392 Gerhard Barth Naples, FL Sound of Music (516) 536-8723(2400) Paul Waldinger (516) 536-6819(9600 Hayes V) *** CANADA *** Another BBS System (416) 465-7752 1:148/208 Mark Bowman Toronto, Canada *** EUROPE *** Fido_N1_1 31-8350-37156 2:500/1 Henk Wevers The Netherlands DUBBS BBS 353-1-885634 n/a Stephen Kearon Dublin, Ireland *** AUSTRALIA *** Sentry BBS 02-428-4687 ... Trev Roydhouse (300-2400) Non-Mail Times (300-19,200) Mail Hour (Trailblazer) Page 30 C NEWS Vol. 1 Issue 13 December 27, 1988 ===================================================================== USER RESPONSE FORM ===================================================================== This form will be included as a regular feature in all future issues of C NEWS. What did you think of the content of this Issue? _____________ _______________________________________________________________ What improvements can you think of that would make C News a better tool for the C Community? _______________________________________________________________ _______________________________________________________________ What is your favorite section or sections? ___________________ _______________________________________________________________ What don't you like about C News? ____________________________ _______________________________________________________________ Additional Comments: _________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ Page 31