Richards M.The BCPL Cintcode and Cintpos user guide.2005

The command stack n causes the size of the coroutine stack allocated for subsequent commands to be n words long. If called without an argument stack outputs the

This command controls the tallying facility which counts the execution of individual Cintcode instructions. If no arguments are given, stats turns on tallying by clearing the tally vector and causing tallying to be enabled for the next command to be executed. Subsequent commands are not tallied, making it possible to process the tally vector while it is in a static state. Typical usage of the stats command is illustrated below:

This command outputs the values pushed into the trace bu®er by the trpush function. These are output in hex, eight values per line with the most recently pushed

mainly describes the Cintpos version. The CLI is the ¯rst program the interacts with after starting the system. Under Cintpos it runs as task one (named Root Cli). It uses variables in the global vector to hold its state during command execution. These variables have reserved global numbers typically in the range 133 to 149. They are declared in g/clihdr.b. Since running commands use the same global vector they can access (and even modify) these variables { a feature that is both dangerous and useful. Commands such as run and c rely on this feature. The CLI global variables are as follows.

cli init CIN:y, POS:y, NAT:y, WCE:y This holds the function used to initialise the CLI, and depends on which context the CLI is to run in. It is called when the CLI is ¯rst entered using the following code.

{LET f = cli_init(parm.pkt)

IF f DO f(result2) // Must get result2 after calling cli_init

}

As can be seen cli init must either return zero or a function that can be applied to result2. The function is typically deletetask or unloadseg with result2 being suitably set.

cli returncode, cli result2 CIN:y, POS:y, NAT:y, WCE:y These hold the return code and the value of result2 of the most recently executed

This variable holds the current prompt string. It should be a writef format string since it used in the Cintpos CLI as follows:

writef(cli_prompt, taskid, mins/60, mins REM 60, secs)

where hours, mins and secs correspond to the current time of day. On single threaded BCPL systems the corresponding call is:

{ writef(cli_prompt, msecs)

where msecs is the real time of execution of the latest command.

The standard input and output streams are those that were setup when the CLI was started. Sometimes a CLI will change its currently selected streams. For instance, while executing a command-command the currently selected input will be from a tempory ¯le of commands. On reaching the end of ¯le input will revert to the standard input.

This holds a collection of bits specifying the context in which the CLI is running. The mnemonics for these bits and their meanings are as follows.

This is an obsolete variable that mainly controlled the generation of prompts. It is

This holds the size of the coroutine stack that the CLI creates every time it runs a command. Its value can be changed by the stack command.

This is either zero or the module of loaded code corresponding to the currently execution command. It is used by the CLI to unload the command when it has ¯nished execution.

* ?

?Print list of debug commands

=Print current value

NPrint next instruction

QQuit

ZEquivalent to P1B9C

\Execute one instruction

, Move down one stack frame

. Move to current coroutine ; Move to parent coroutine [ Move to first coroutine

] Move to next coroutine

*

The debugger has a current value that can be loaded, modi¯ed and displayed. For example:

Four areas of memory, namely: the global vector, the current stack frame, the Cintcode register, and 10 scratch variables are easily accessed using the letters G, P, R, V, respectively.

Notice that values that appear to be entry points display the ¯rst 7 characters of the function's name. Other display styles can be speci¯ed by the commands $C, $D, $F, $B, $O, $S, $U or $X. These respectively display values as characters, decimal number, in function style (the default), binary, octal, string, unsigned decimal and hexadecimal.