User guide

Chapter 3

The Library

This manual describes three var i ants of the BCPL system. The simplest is in-

voked by the shell command cintsys and provides a single t h r eaded command

language interpreter. The system invoked by cintpos provides a mul t i -t hreaded

system where the in d i vi d u a l threads (called tasks) are ru n in parallel and are

pre-emptible. A third version is available for some architectures and provides a

single threaded version in which the BCPL source is compiled into native machine

code. Although this version is faster, it is more machine dependent, has fewer

debugging aid s and will only run a single command.

The libraries of these three systems have much in common and so are all

described t oget her. The description of all constants, variables and fun ct i ons have

a right justiﬁed l i n e such as the following

CIN:y, POS:y, NAT:n

where CIN:, POS: and NAT: denote t he single threaded, multi-threaded and native

code versions, respectively, and the letters y and n stand for yes and no, showing

whether the corresponding constant, variable or function is available on that

version of the system.

The resident library functions, var i ab l es and manifest constants are declared

in the standard library header ﬁle g/libhdr.h. Most of the functions are deﬁn ed

in BCPL in eit h er sysb/blib.b or sysb/dlib.b, but three function s (sys, chgco

and muldiv) are in the hand written Cintcode ﬁle cin/syscin/syslib. Most

functions relat i n g to the multi-thr ead e d version are deﬁned in klib.b.

The following three sections describe the manifest con st a nts, variables and

functions (in alphabetical order) provided by the standard library.

3.1 Manifest constant s

B2Wsh CIN:y, POS:y, NAT:y

This constant hol ds the shift required to convert a BCPL pointer into a byte address.