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LZW Data Compression Library For the C Language (LZW4C) USERS MANUAL Version 1.4 June 1, 1994 This software is provided as-is. There are no warranties, expressed or implied. Copyright (C) 1994 All rights reserved MarshallSoft Computing, Inc. Post Office Box 4543 Huntsville AL 35815 205-881-4630 Voice / FAX 205-880-9748 Support BBS _______ ____|__ | (R) --| | |------------------- | ____|__ | Association of | | |_| Shareware |__| o | Professionals -----| | |--------------------- |___|___| MEMBER LZW4C Users Manual Page 1 C O N T E N T S Chapter Page 1.0 Introduction..............................................3 1.1 Distribution Files....................................3 1.2 Compiling the Library.................................4 1.3 User Support..........................................4 1.4 ASP Ombudsman.........................................5 1.5 Installation..........................................5 2.0 The LZW Algorithm.........................................6 2.1 LZW Compression.......................................6 2.2 LZW Expansion.........................................7 2.3 LZW Implementation....................................7 3.0 Example Programs..........................................8 3.1 COMPRESS..............................................8 3.2 EXPAND................................................8 3.3 MK_ARC................................................8 3.4 UN_ARC................................................9 3.5 SEE_ARC...............................................9 3.6 EX_ARC................................................9 3.7 TEST_LZW..............................................9 4.0 Reader & Writer Functions................................10 5.0 Library Functions........................................11 5.1 InitLZW..............................................11 5.2 TermLZW..............................................11 5.3 Compress.............................................12 5.4 Expand...............................................12 6.0 Error Codes..............................................13 6.1 EXPANSION_ERROR......................................13 6.2 CANNOT_ALLOCATE......................................13 6.3 INTERNAL_ERROR.......................................13 6.4 NOT_READY............................................13 6.5 BAD_BITCODE..........................................13 7.0 Legal Issues.............................................14 7.1 Registration.........................................14 7.2 Referral Plan........................................14 7.3 License..............................................15 7.4 Warranty.............................................15 8.0 Revision History.........................................16 9.0 Other MarshallSoft Computing Products for C..............17 9.1 The Personal Communications Library for C............17 9.2 The Personal Protocol Library for C..................17 9.3 The EMS Expanded Memory Library for C................18 LZW4C Users Manual Page 2 1.0 Introduction LZW4C consists of a variable code size implementation of the LZW (Lempel-Ziv-Welch) algorithm for compressing and decompressing data. LZW does particularly well on text files, achieving better than a 50 % compression ratio for many files. The LZW algorithm is considered to be one of the best general purpose algorithms available today. The new high speed modems that employ on-the-fly data compression (such as MNP 5.0 & the V.42 bis international standard) use the LZW algorithm, as well as such well known utility programs such as PKZIP. The LZW4C library is designed to be used in a wide variety of situations. Some of the possible uses include: 1) Compression and expanding files on disk. 2) Compressing files "on the fly" before sending over a modem, and then expanding on the receiving end. 3) Compression of data files used by your application program such as help files, graphics screens, etc. The compressed data files are then expanded as they are loaded by the application. 1.1 Distribution Files The distribution files are as follows: 1) LZW4C_C.LIB -- COMPACT model library. 2) LZW4C_L.LIB -- LARGE model library. 3) LZW4C_L.MIX -- LARGE model library (MIX only). 4) LZW4C.DOC -- This documentation file. 5) LZW4C.INV -- Invoice file. 6) COMPRESS.C -- Data compression example program. 7) EXPAND.C -- Data expansion example program. 8) LZW4C.H -- Library prototypes. 9) *._T_ -- Turbo C makefiles. 10) *._M_ -- Microsoft C makefiles. 11) X_*.BAT -- MIX Power C batch file. 12) RW_IO.C -- Reader/Writer I/O source file. 13) RW_IO.H -- Reader/Writer prototype file. 14) DIR_IO.C -- Directory I/O source file. 15) DIR_IO.H -- Directory I/O prototype file. 16) SAYERROR.C -- Displays text error messages. 17) TEST_LZW.C -- LZW test driver program. 18) MK_ARC.C -- File archiving program. 19) UN_ARC.C -- File un-archiving program. 20) SEE_ARC.C -- Program to list archived files. 21) EX_ARC.C -- Program to extract file from archive. Registered users also receive: 1) LZW4C.ASM -- SOURCE CODE for the LZW4C libraries. 2) MAKE_C.BAT -- Batch file to make LZW4C_C.LIB 3) MAKE_L.BAT -- Batch file to make LZW4C_L.LIB 4) MAKE_XL.BAT -- Batch file to make LZW4C_L.MIX LZW4C Users Manual Page 3 1.2 Compiling the Library LZW4C requires rather large work buffers at run time. This requires "far" data pointers which in turn means that you must compile using either the COMPACT memory model (with "near" code pointers) or the LARGE memory model (with "far" code addresses). There are, therefore, two memory model libraries provided: lzw4c_c.lib -- Compact memory model library. lzw4c_l.lib -- Large memory model library. lzw4c_l.mix -- Large memory model library (MIX only). The registered user can re-compile the source code (source code is provided in the registered version only) for the library using one of the two provided batch files: make_c.bat -- Creates lzw4c_c.lib. make_l.bat -- Creates lzw4c_l.lib. make_xl.bat -- Create lzw4c_c.mix. Using the COMPACT memory model will result in a slightly smaller and faster executable than using the LARGE memory model. Be sure to compile all of your code for the correct memory model. Refer to your compiler manual for more information on memory models. 1.3 User Support We want you to be successful in developing your application using our libraries! We depend on our customers to let us know what they need in a library. This means we are committed to providing the best libraries that we can. If you have any suggestions or comments, please write to us or give us a call. If you are having a problem using LZW4C or any of our libraries, call (205) 881-4630 between 5 PM and 9 PM CST Monday through Friday. You can call at other times and leave a message, and call back later during our regular business hours for a reply. You can also FAX us at this same number at any time. You may also call our 24 hour BBS (2400 baud, no parity, 8 data bits, 1 stop bit) at any time. The BBS will contain the latest shareware version of LZW4C, messages, and other related files. All files are in standard ZIP format. You can leave a message on the BBS, and we will usually have a reply ready for you within 24 hours. The dedicated telephone number is 205-880-9748. Set your modem for 1200 to 9600 baud, 8 data bits, no parity, one stop bit. The MarshallSoft Computing, Inc. newsletter "Comm Talk" is published quarterly. It discusses various communications problems and solutions using PCL4C (the communications library) as well as related information such as data compression issues. Registered users receive a one year complimentary subscription when first registering and for each update purchased. However, overseas customers who want the newsletter must pay $5 for postage. Additional one year subscriptions are $15 plus $5 for postage for overseas customers. LZW4C Users Manual Page 4 1.4 ASP Ombudsman MarshallSoft Computing, Inc. is a member of the Association of Shareware Professionals (ASP). ASP wants to make sure that the shareware principle works for you. If you are unable to resolve a shareware-related problem with an ASP member by contacting the member directly, ASP may be able to help. The ASP Ombudsman can help you resolve a dispute or problem with an ASP member, but does not provide technical support for members' products. Please write to the ASP Ombudsman at 545 Grover Road, Muskegon, MI USA 49442-9427, Fax 616-788-2765, or send a CompuServe message via CompuServe Mail to ASP Ombudsman 70007,3536. 1.5 Installation (1) Microsoft C, Borland & Turbo C, and MIX Power C compilers are supported. However, the code should work with most any C compiler. Before installation of LZW4C, your C compiler should already be installed on your system and tested. If you are not familiar with makefiles, refer to your compiler manual. If you are using the interactive environment for Quick C or Turbo C, be sure to compile with the memory model corresponding to the LZW4C library used. (2) Make a backup copy of your distribution disk. Put your original distribution disk in a safe place. (3) Create a work directory on your work disk (normally your harddisk). For example, to create a work directory named LZW4C, we first log onto the work disk and then type: MKDIR LZW4C (4) Copy all the files from your backup copy of the distribution disk to your work directory. For example, to copy from the A: drive to your work directory, we type: CD LZW4C COPY A:*.* (5) Compile COMPRESS.C, EXPAND.C, TEST_LZW.C and link with the appropriate LZW4C library (they use the COMPACT library except for MIX Power C). For example, to make COMPRESS.EXE: a) Borland Turbo C: Type MAKE -fCOMPRESS._T_ b) Microsoft C: Type MAKE COMPRESS._M_ c) MIX Power C: Type (LARGE model only) X_COMPRESS LZW4C Users Manual Page 5 2.0 The LZW Algorithm The following discussion of the LZW algorithm is meant to provide a high level overview of LZW. For those interested in a more detailed explanation, several good books are available on data compression. The original research papers on what is now called LZW compression are: J. ZIV and A. Lempel, "A Universal Algorithm for Sequential Data Compression", IEEE Transactions on Information Theory, May 1977. Terry Welch, "A Technique for High-Performance Data Compression", Computer, June 1984. 2.1 LZW Compression The LZW compressor reads 8-bit bytes from a data source and outputs N-bit codes each of which identifies a previously defined string. The value of N starts at 9. Thus, codes 0 through 255 (0xff) correspond with the standard character set, while codes 256 (0x100) through 511 (0x1ff) correspond to a byte-byte pair or a code-byte pair in the code table. After code 511 is output, 10 bit codes are used. This is repeated until the maximum number of bits per code is reached. LZW4C can use a maximum value of 12, 13 or 14 bits per code. The recommended value is 14. The LZW compressor builds a code table as it compresses data. The code table consists of previously encountered strings. The basic LZW compression algorithm is as follows: STRING = get first input byte while there is more input data {BYTE = get next input byte if STRING+BYTE is in code table STRING=STRING+BYTE else {output code for STRING add STRING+BYTE to code table STRING = BYTE } } output the code for STRING LZW4C Users Manual Page 6 2.2 LZW Expansion The LZW expansion routine reads the N-bit codes previously created by the LZW compressor and reconstructs the code table (as previously constructed by the compressor) as it is outputing 8-bit bytes. A code corresponds to a single byte (the first 256 codes from 0x00 through 0xff), or a byte-byte pair in the code table, or a code-byte pair in the code table. In the later case, the code part of the code-byte pair refers to another defined code pair in the table. As each code is read in, it is located in the code table and the corresponding 8-bit bytes are output. This means that codes must be defined before they are needed for expansion. Unlike older dictionary based compression schemes, the code dictionary produced by the compressor routine does not have to be provided to the expansion routine. The basic LZW de-compression algorithm is as follows: OLDCODE = input first code output OLDCODE while there is more input data {NEWCODE = get next input code STRING = translation of NEWCODE output STRING BYTE = 1st byte of STRING add OLDCODE+BYTE to the code table OLDCODE = NEWCODE } 2.3 Implementation The LZW4C library is written in assembly language. Any Microsoft or compatible assembler will assemble it. The decision to program LZW4C in assembler was made in order to get the absolute maximum performance possible. Although optimized C is very good, it is still bigger and slower than hand optimized assembler. The LZW algorithm requires more temporary working data space than is available in the SMALL or MEDIUM memory models. Therefore, there are no SMALL or MEDIUM memory model libraries provided, but there are COMPACT (lzw4c_c.lib) and LARGE (lzw4c_l.lib) memory model libraries. Use the COMPACT memory model when your code will fit into 64KB or less, otherwise you must use the LARGE memory model. Refer to your compiler manual for a complete discussion of memory models. Using a maximum of 12 bits per code (see the InitLZW() function), 25105 bytes are allocated for table space. This value jumps to 45145 bytes when using 13 bytes and 90205 bytes when using 14 bits. The best compression is given using 14 bits per code. LZW4C Users Manual Page 7 3.0 Example Programs Six example programs are provided. Each example program should be compiled with the provided makefile. These example programs are meant to demonstrate various ways in which the LZW compression library can be used. If you are using an integrated compiler environment instead of makefiles, notice that each program is compiled with the COMPACT memory model. 3.1 COMPRESS The program COMPRESS is provided as both a standalone LZW compression program, and as an example of how to use the LZW4C library to compress a file. In order to run COMPRESS, type COMPRESS <infile> <outfile> For example, to compress LZW4C.DOC to LZW4C.LZW, type COMPRESS LZW4C.DOC LZW4C.LZW 3.2 EXPAND The program EXPAND is provided as both a standalone LZW de-compression program, and as an example of how to use the LZW4C library to de-compress a file. In order to run EXPAND, type EXPAND <infile> <outfile> For example, to de-compress LZW4C.LZW to LZW4C.DOC, type COMPRESS LZW4C.LZW LZW4C.DOC Of course, you can only decompress a file that has been compressed with COMPRESS. 3.3 MK_ARC The program MK_ARC is used to create an archive file. For example, to create an archive named C.ARF consisting of all files ending with the extension '.C', type: MK_ARC *.C C.ARF LZW4C Users Manual Page 8 3.4 UN_ARC The program UN_ARC is used to un-archive the files archived by MK_ARC. For example, to un-archive C.ARF, type: UN_ARC C.ARF Note that the UN_ARC program can be modified to provide for a customized product installation program. 3.5 SEE_ARC The program SEE_ARC is used to list the files in any archive file created with MK_ARC. For example, to see the files in C.ARF: SEE_ARC C.ARF 3.6 EX_ARC The program EX_ARC is used to extract a file from an archive. For example, to extract DEMO.C from C.ARG, type: EX_ARC DEMO.C C.ARF 3.7 TEST_LZW The program TEST_LZW is used to compress, expand, and verify one or more files. It's purpose is for you to test the LZW4C library on your own files. Your files are never modified. However, you can NOT specify a file named "XXX.XXX" or "YYY.YYY" since these files are work files used by COMPRESS and EXPAND. Compression ratios ( compressed_size / original_size ) are printed for each file compressed. For example, to test all files ending with a *.C extension, type: TEST_LZW *.C After compiling TEST_LZW, run it against a large directory of files as a test of the library. TEST_LZW can also be run with a maximum of 12 or 13 bits per code rather than the standard 14 bits (the preferred value). To test all files ending with a *.C extension using a maximum of 13 bits per code, type: TEST_LZW *.C 13 All example code should be compiled using the COMPACT memory model (FAR data pointers, NEAR code pointers). You may create a LARGE memory model version of the above five programs by re-compiling as LARGE memory model programs. LZW4C Users Manual Page 9 4.0 Reader & Writer Functions Both the compression and expansion routines in the LZW4C library use Reader and Writer functions supplied by the library caller. They are provided as a means of giving the caller complete control over the source and destination of the data stream during compression and expansion. A reader function is not limited to reading from disk. It may read from any data source as long as it returns a -1 when there is no more data to be read. Similiarly, a writer function may write to any data sink. A simple example of suitable reader and writer functions which can be used to compress and expand files on disk are as follows: int Reader() { return(fgetc(FileInp)); } int Writer(Byte) char Byte; { return(fputc(Byte,FileOut)); } where FileInp correspond to the input stream and FileOut corresponds to the output stream: FILE *FileInp; FILE *FileOut; FileInp = fopen(<input_file_name>,"rb"); FileOut = fopen(<output_file_name>,"wb"); Note that the Reader returns a -1 for an end of data condition. Data is returned as an integer with the high byte set to 0. Thus, the only integers can can be returned by the Reader are -1 (0xffff) and 0 (0x0000) to 255 (0x00ff). If you remove data from a character buffer, be sure to zero out the high order byte (AND with 0x00ff) unless you are returning a -1 (EOF). For an example, examine the code for the Reader() function in RW_IO.C. LZW4C Users Manual Page 10 5.0 Library Functions There are four functions in the LZW4C library as follows: 5.1 InitLZW Function: Initialize library Prototype: int InitLZW(Alloc,BitCode) void (*Alloc)(); /* pointer to allocate function */ int BitCode; /* maximum bits per code */ Description: The InitLZW function is used to initialize the library. The first argument is the function name of a user supplied memory allocation function. Use the standard C library function malloc() unless you wish to use your own memory management function. The second argument <BitCode> is the maximum number of bits used per code in the compression process. Legal values are 12, 13, and 14 (the preferred value). Smaller values will use less memory but not compress as tightly. Returns: -2 : (CANNOT_ALLOCATE) -- if unable to allocate. -5 : (BAD_BITCODE) -- BitCode not 12, 13, or 14. 0 : (AOK) -- no error. Example: /* initialize LZW4C */ char *malloc(); InitLZW(malloc,14); 5.2 TermLZW Function: Terminate library Prototype: int TermLZW(Free) void (*Free)(); /* pointer to free function */ Description: The TermLZW function is used to terminate the library after all processing is done. The single argument is the function name of a user supplied memory de-allocation function. This is primarily a way to free memory allocated by InitLZW. Use the standard C library function free() unless you wish to use your own memory management free function. Returns: 0 : (AOK) -- no error. Example: /* terminate LZW4C */ TermLZW(free); LZW4C Users Manual Page 11 5.3 Compress Function: Compresses a data set. Prototype: int Compress(Reader,Writer) int (*Reader)(); /* pointer to Reader() */ int (*Writer)(); /* pointer to Writer() */ Description: The Compress function is used to compress a data set. The Reader function always returns the next input byte. The Writer function consumes the next output byte. Refer to the section on Reader/Writer I/O. Returns: -4 : (NOT_READY) -- Didn't call InitLZW() first. 0 : (AOK) -- No error. Example: /* compress a file */ FILE *FileInp, *FileOut; FileInp = fopen("LZW4C.DOC","rb"); FileOut = fopen("LZW4C.LZW","wb"); Compress(Reader,Writer); int Reader() {return(fgetc(FilePtr));} int Writer(Byte) int Byte; {return(fputc(Byte,FilePtr));} 5.4 Expand Function: Expands a file. Prototype: int Expand(Reader,Writer) int (*Reader)(); /* pointer to Reader() */ int (*Writer)(); /* pointer to Writer() */ Description: The Expand function is used to de-compress a file previously compressed with the Compress function. The Reader function always returns the next input byte. The Writer function consumes the next output byte. Refer to the section on Reader/Writer I/O. Returns: -1 : (EXPANSION_ERROR) -- File not compressed by the compress function. 0 : (AOK) -- No error. Example: /* de-compress a file */ FILE *FileInp, *FileOut; FileInp = fopen("LZW4C.DOC","rb"); FileOut = fopen("LZW4C.LZW","wb"); Expand(Reader,Writer); LZW4C Users Manual Page 12 6.0 Error Codes Be sure and check the return codes from each LZW4C function call. There are only 5 error codes returned by the LZW4C library other than 0 (no error). All error codes are negative numbers. Their numerical values are in the LZW4C.H file. Each error code is returned by a library function as follows: **************************************************************** * Error Name * IntLZW * TermLZW * Compress * Expand * **************************************************************** * EXPANSION_ERROR * No * No * No * Yes * * CANNOT_ALLOCATE * Yes * No * No * No * * INTERNAL_ERROR * Yes * No * No * No * * NOT_READY * No * No * Yes * Yes * * BAD_BITCODE * Yes * No * No * No * **************************************************************** 6.1 EXPANSION_ERROR An EXPANSION_ERROR error is returned only by the Expand() library function. It is caused by attempting to expand a file that was not compressed by the Compress() function. Note, however, that Expand() may expand a file that was not compressed by Compress() without returning an EXPANSION error. 6.2 CANNOT_ALLOCATE A CANNOT_ALLOCATE error is returned only by the InitLZW() library function. It is caused when the Alloc() function passed to InitLZW() returns a NULL pointer, indicating that it cannot allocate sufficient memory. 6.3 INTERNAL_ERROR An INTERNAL_ERROR error is returned only by the InitLZW() library function and only in the shareware version. It is caused by modification of the Shareware screen. You should never get this error. 6.4 NOT_READY A NOT_READY error is returned by the Compress() and Expand() library functions. It is caused by calling Compress() or Expand() without first calling InitLZW(). 6.5 BAD_BITCODE A BAD_BITCODE error is returned from InitLZW() when specifing a BitCode of other than 12, 13, or 14. LZW4C Users Manual Page 13 7.0 Legal Issues 7.1 Registration If you wish to register the LZW4C Library, please send $45 plus $3 S&H ($6 outside of North America) to: MarshallSoft Computing, Inc. Post Office Box 4543 Huntsville AL 35815 We accept American Express (account number, expiration date, exact name on your card, and complete AmEx billing address required), checks in US dollars drawn on a US bank, purchase orders (POs) from recognized US schools and companies listed in Dun & Bradstreet, and COD (street address and phone number required) within the USA (plus a $3 COD charge). Print the file PCL4C.INV if an invoice is needed. You can also order LZW4C from The Public Software Library (PSL) with your MC, Visa, AmEx, or Discover card by calling 800-242-4PSL (from overseas: 713-524-6394) or by FAX at 713-524-6398 or by CompuServe at [71355,470]. THESE NUMBERS ARE FOR ORDERING ONLY. The product number for LZW4C is 10910. If you wish to update from an older version of LZW4C, send $15 plus $3 S&H ($6 outside of North America). Updates must be ordered directly from MarshallSoft Computing. The registered package includes: o Small, medium, compact & large LZW4C libs w/o shareware screen. o Assembler source code for the library. o Laser printed Users Manual. o Telephone / FAX / BBS support for one year. Print the file LZW4C.INV if an invoice is needed. The registered user will receive the latest version of LZW4C shipped by two day priority mail (packet airmail overseas). A 5.25" diskette is provided unless a 3.5" diskette is requested. 6.2 Referral Program The registered user will receive a $5 certificate towards any MarshallSoft Computing product by referring a new customer (someone who has never registered anything with us) paying full price ($55). The new customer must identify you at the time the order is placed. You will be mailed a $5 certificate when the new registration is paid. LZW4C Users Manual Page 14 7.2 License MarshallSoft Computing, Inc. grants the registered user of LZW4C the right to use the LZW4C library (in object form) in the development of any software product without any royalties. However, the source code for the library (LZW4C.ASM) is copyrighted by MarshallSoft Computing Inc., and may not be released in whole or in part. 7.3 Warranty MARSHALLSOFT COMPUTING, INC. DISCLAIMS ALL WARRANTIES RELATING TO THIS SOFTWARE, WHETHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, AND ALL SUCH WARRANTIES ARE EXPRESSLY AND SPECIFICALLY DISCLAIMED. NEITHER MARSHALLSOFT COMPUTING, INC. NOR ANYONE ELSE WHO HAS BEEN INVOLVED IN THE CREATION, PRODUCTION, OR DELIVERY OF THIS SOFTWARE SHALL BE LIABLE FOR ANY INDIRECT, CONSEQUENTIAL, OR INCIDENTAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE SUCH SOFTWARE EVEN IF MARSHALLSOFT COMPUTING, INC. HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES OR CLAIMS. IN NO EVENT SHALL MARSHALLSOFT COMPUTING, INC.'S LIABILITY FOR ANY SUCH DAMAGES EVER EXCEED THE PRICE PAID FOR THE LICENSE TO USE THE SOFTWARE, REGARDLESS OF THE FORM OF THE CLAIM. THE PERSON USING THE SOFTWARE BEARS ALL RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE. Some states do not allow the exclusion of the limit of liability for consequential or incidental damages, so the above limitation may not apply to you. This agreement shall be governed by the laws of the State of Alabama and shall inure to the benefit of Marshallsoft Computing, Inc. and any successors, administrators, heirs and assigns. Any action or proceeding brought by either party against the other arising out of or related to this agreement shall be brought only in a STATE or FEDERAL COURT of competent jurisdiction located in Madison County, Alabama. The parties hereby consent to in personam jurisdiction of said courts. LZW4C Users Manual Page 15 8.0 Revision History Version 1.0 -- October 8, 1992 o Original release. Version 1.1 -- November 11, 1992 o Added MK_ARC.C example program. o Added UN_ARC.C example program. Version 1.2 -- March 1, 1993 o Added SEE_ARC example program. o Minor speed improvements. Version 1.3 -- Sept 10, 1993 o Added BitCode parameter to InitLZW. o LZW4C.H modified for use with both C and C++. Version 1.4 -- June 1, 1994 o Added EX_ARC.C example program. o Minor documentation changes. LZW4C Users Manual Page 16 9.0 Other MarshallSoft Computing Products for C Shareware versions of all MarshallSoft Computing products are available on our user support BBS at 205-880-9748 (1200 to 9600 baud, 8N1). 9.1 The Personal Communications Library for C The Personal Communications Library for the C Language (PCL4C) is an asynchronous communications library designed for experienced software developers programming in C. Four compilers are supported: Microsoft Optimizing C, Microsoft Quick C, Borland Turbo C, and MIX Power C. An IBM PC/XT/AT or compatible is required. The PCL features: o SMALL, COMPACT, MEDIUM & LARGE memory models. o 36 communications and support functions. o Supports the high performance INS16550 UART. o Supports hardware (RTS/CTS) flow control. o Interrupt driven transmitter (optionally) & receiver. o Supports 300 baud to 115,200 baud. o Supports COM1 through COM16. o Adjustable receive queues from 8 bytes to 32 KB. o Control-BREAK error exit. o 17 communications error conditions trapped. o Support the PC/4 and PC/8 DigiBoards. o Supports the BB1004, BB1008, and BB2016 BOCA boards. o Allows 4 - 16 ports to run concurrently. o Complete modem control & status. o Written in assembly language for small size & high speed. o Terminal program featuring XMODEM, YMODEM, & YMODEM-G. The Personal Communications Library for C (PCL4C) is available for $65 plus $3 S&H ($6 S&H overseas). It may be ordered at the same time as the Personal Protocol Library for $75 plus $3 S&H ($6 overseas). 9.2 The Personal Protocol Library for C The Personal Protocol Library (PPL) consist of a state driven library which implements the XMODEM, XMODEM-CRC, XMODEM-1K, XMODEM-G, YMODEM, and YMODEM-G file transfer protocols. This allows the programmer to run multiple protocol transfers simultaneously while interacting with the user at the keyboard. The Personal Protocol Library for C (PPL4C) is available for $35 plus $3 S&H ($6 S&H overseas). Both the Communications library and the Protocol library can be ordered together for $75. The PPL requires the Personal Protocol Library for C (PCL4C) as described above. LZW4C Users Manual Page 17 9.3 The EMS Expanded Memory Library The EMS4C library implements version 3.2 of the LIM (Lotus-Intel-Microsoft) specification for expanded memory. It will run with either version 3.2 or 4.0 of the LIM specification. The EMM4C library (included with the EMS4C library) is an expanded memory manager which allows C programmers to allocate and free EMS (expanded) memory similiar to malloc() and free() in the standard C runtime library. Both EMM4C and EMS4C require that your system be configured with expanded (EMS) memory. But, 386 & up systems can use extended memory as expanded memory. The EMS Expanded Memory Library for C is available for $35 plus $3 S&H ($6 S&H overseas). LZW4C Users Manual Page 18