Peter H. Salus is the author of A Quarter Century of UNIX (1994) and Casting the Net: From ARPANET to Internet and Beyond (1995). He is an internationally recognized expert and has been the keynote speaker at Uniforum Canada, the UKUUG, the NLUUG, and the OTA (Belgium) in the past few years. He has been executive director of the USENIX Association and of the Sun User Group and vice president of the Free Software Foundation. He was the managing editor of Computing Systems (MIT Press) from 1987 to 1996. He writes on a variety of computing topics in a number of magazines. His Ph.D. in linguistics (New York University, 1963) has led him from natural languages to computer languages.

The aim of the Handbook of Programming Languages is to provide a single, comprehensive source of information concerning a variety of individual programming languages and methodologies for computing professionals. The Handbook is published in multiple volumes and covers a wide range of languages, organized by type and functionality.

The Handbook includes four volumes:

Volume I: Object-Oriented Programming Languages

This volume contains chapters on Smalltalk, C++, Eiffel, Ada95, Modula-3, and Java.

Volume II: Imperative Programming Languages

This volume contains chapters on Fortran, Pascal, Icon, and C, as well as a chapter on intermediate languages by Ron Cytron.

Volume III: Little Languages and Tools

This volume contains chapters on little languages and domain-specific languages, such as troff, awk, sed, Perl, Tcl and Tk, Python, and SQL. It also contains seminal work by Brian Kernighan and Lorinda Cherry as well as Jon Bentley and essays by Paul Hudak and Peter Langston.

Volume IV: Functional and Logic Programming Languages

This volume contains chapters on functional (Lisp, Scheme, Guile, and Emacs Lisp) and logic (Prolog) programming languages.

Foreword to This Volume: Imperative Programming Languages

On the simplest level, imperative programming languages are those that manipulate data in a stepwise fashion. That is, they take sequential instructions (algorithms) and apply them to data of various kinds.

Imperative languages have a “do this, then do that’’ structure. These instructions or commands are usually called statements. Most of the data items in memory have names, which are used when manipulating those items. The properties of the data items are called types. Programmers specify the relationships among representations, types, data, and names in data declarations.

A data declaration imposes structure upon data and gives it a name. The imposed structure is a specified type; the name is an identifier. All data is stored as bits. The bit pattern and the structure determine the data item’s value. The union of name, type and value is called a variable.