Before C » Linux Magazine

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The venerable BCPL procedural structured programming language is fast to compile, is reliable and efficient, offers a wide range of software libraries and system functions, and is available on several platforms, including the Raspberry Pi.

In the 1960s, the main high-level programming languages were Fortran, Basic, Algol 60, and COBOL. To optimize code or to provide low-level operations, assembler programming offered the only means to access registers and execute specific machine instructions. BCPL, which was used as a teaching language in many universities, provided a language with a rich syntax, addressed the scoping limitations of the other languages, and had low-level operations such as bit manipulation and computation of variable addresses.

Where BCPL differs from the other languages is that it is typeless; all variables are considered to be a word, typically 16 or 32 bits. Programmers can access individual bits and bytes of a word, perform both arithmetic and logical operations on words, compute the address of a word, or use a word as a pointer to another word. One further novel aspect of BCPL is that the compiler is small and written in BCPL, producing intermediate code for a virtual machine and simplifying the development of the compiler for a wide range of computers. BCPL was used on mainframe computers and minicomputers in the 1970s and microprocessors in the 1980s.

The early developers of Unix were influenced by, and many aspects of C were adopted directly from, BCPL. Although BCPL also supported characters and bytes, the lack of richer types was addressed in C, which became the programming language of choice for Unix (and subsequently Linux), leaving BCPL mostly for academic applications. Several groups developed compilers, operating systems, software utilities, commercial packages, and even flight simulation software in BCPL, but for the most part, BCPL has been forgotten.

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