The Kermit file transfer protocol was developed at the Columbia University Center for Computing Activities in 1981 as a mechanism for transferring text and binary files through a dial-up or other unreliable communications link. It could achieve a reasonable rate of transmission through links that could only transmit visible ASCII characters by transforming other characters into two-character sequences. And it was able to achieve a high level of integrity by packing characters into blocks with one or more checksum characters at the end of each block.

Since that time, Kermit has been the subject of a continuing development program, with new releases now appearing a couple of times each year. The file transfer mechanism has been extended so that the communicating machines can automatically negotiate block lengths, checksum arrangements, compression capabilities, and so on. Kermit source code has been made available publicly, and the program has been adapted for use on almost every type of computer. It has therefore been widely accepted. The transfer of files between machines usually necessitates an initial logon phase, during which an operator is required to enter modem-control and other commands interactively via a keyboard. The  Kermit  protocol is therefore equipped with a terminal-emulation capability, and it is often employed as a vehicle for simple terminal sessions with computers at remote locations. C-Kermit is so named because it is implemented in the C language. It can be compiled for use under a wide variety of UNIX and proprietary operating systems, such as IBM mainframe, DEC, and HP. da Cruz is well known for his efforts in coordinating Kermit’s development.

The first four chapters provide a brief introduction to C-Kermit’s capabilities, and describe how it can be obtained and how its execution can be initiated. Its syntax and basic command set are also covered.

Chapters 5 and 6, respectively, introduce some basic and some more complex (IBM mainframe and X.25) file transfer examples. Procedures are given for changing packet-start characters so C-Kermit can cope with multiplexers that react to the characters normally used, and for changing the checksum arrangement so trailing blanks will not be generated. I have been a user of C-Kermit for some years, and most commonly employ it in “server” mode for convenience of use during file transfers. I have often wondered how some of its more advanced capabilities (such as sliding windows) might be used to enhance its performance over long-distance dial-up links. Both these issues are addressed in chapters 7 and 8. In a related vein, some suggestions for transferring files to and from machines not equipped with any form of Kermit are given in chapter 10.

C-Kermit has some capabilities that might be considered inappropriate in a communications program. Those readers who wish to use it for translating proprietary (such as Macintosh Quickdraw) or non-English (such as Kanji or Finnish) character sets in transit can learn how in chapter9. C-Kermit also has a comprehensive scripting language of its own, with built-in functions, user-definable macros, and so on. The use of this language is illustrated in chapters 11 through 13; some sample login scripts for UNIX, VMS, IBM mainframes, and commercial data services are included. The final chapter illustrates how C-Kermit can be invoked with command-line options for convenience in shell scripts or where it has been compiled without an interactive capability. A listing of available options is included.

The appendices include an overall command reference, a condensed guide to serial data communications, some character set tables, and some C utility program listings. Separate appendices cover installation and usage peculiarities for each of the major operating systems under which C-Kermit can be used. Some valuable references are included in a short bibliography. The book concludes with an index that is both useful and accurate. I was unable to find any major typographical or other errors.

If you need to connect to, or transfer files to, remote computers in an environment other than MS-DOS, then you could be using C-Kermit, and this book is for you. Even if you are already using a C-Kermit equivalent such as Z-modem, you will find much of the communications and other general information useful; you may also find that C-Kermit can offer some advantages in particular circumstances. You will recover the book’s reasonable purchase price in a short time through the savings it will enable you to realize in communications costs and in the costs of your own labor.