B (programming language)

B is the name of a programming language developed at Bell Labs, the predecessor of the C programming language.

It was largely a work of Kenneth L. Thompson with contributions from Dennis M. Ritchie first published in 1969 ^{[citation needed]}.

History

B was essentially a simplification of the BCPL language, removing whatever components Thompson considered dispensable so that it would fit into the memory of the minicomputers of the day. The language also included some changes according to Thompson's preferences (mostly to reduce the number of characters in a typical program).

Like BCPL, and FORTH, B had only one data type, which corresponded to a machine word. Most operators handled it as an integer; for example + (addition), - (subtraction), * (multiplication), or / (division). Other operators treated it as a memory address to reference: a pointer. B offered operators that allowed obtaining the address of a given variable, or writing to the address pointed to by a pointer variable.

The first implementations were for the PDP-7 and PDP-11 minicomputers running older versions of UNIX; and for 36-bit Honeywell mainframes running the GCOS system.

Evolution

The typeless nature of B made sense on the Honeywell, PDP-7, and many other older computers, but was a problem on the PDP-11 because character types were hard to access of data that the PDP-11 and most modern computers support. Starting in 1971, Ritchie made changes to the language at the same time that he converted his compiler to produce native machine language. The most notable was the addition of different data types for variables.

During 1971 and 1972 B first evolved into "New B" (New B, NB) and then into C. Later, in early 1973, a preprocessor was added at the request of Alan Snyder.

The effort was comprehensive enough this year that over the summer the UNIX system kernel for the PDP-11 was rewritten in C.

During the period 1972-1973 there was a need to port it to the Honeywell 635 and IBM 360/370, so Mike Lesk wrote the "portable I/O package" which would become the "Standard I/O" (standard I/O or stdio) of the C language.

B continued to be used into the 1990s on Honeywell mainframes and certain embedded systems for a variety of reasons, including limited hardware use in these systems; extensive libraries, tools; or simply because he was good enough to do the job.

Name

B was greatly influenced by BCPL, and his name was probably a contraction of "BCPL". However it is possible that his name was based on the Bon programming language, an older language unrelated to B, designed by Thompson for use in MULTICS.

Examples

The following example function is taken from the Users' Reference to B by Ken Thompson:

/* The following function prints a non-negative number, n, base b, where 2 Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â This routine uses the fact that in the ASCII character game, digits 0 to 9 They have sequential code values. */printn(n,b) { extern Fucking; car a; if(a=n/b) /* assignment, not equality check */ printn(a, b); /* recursive */ Fucking(n%b + '0');!

This example program in B uses the above function to add three numbers by printing the result on the screen.

main( ) { extern printn; car a, b, c, sum; a = 1; b = 2; c = 3; sum = a+b+c; printn(sum,10);!