I. J Note on Bug Reporting
11. THE SYSTEM COMMANDS
Users' Manual System Commands
This chapter includes a discussion of the commands at the System level, and a full description of each command. This is the outer level of System control, and these commands invoke basic System functions such as calling the Compiler, the Editor, the Filer, etc.
You may think of the System command level (the "outer" level) as the chief control for the entire System, which indeed it is -- you have already (in Figure 1) seen the System diagrammed as a tree of command levels, with the System commands as the outer level available from the root node.
I t is also convenient, and in some ways more useful, to think of the System level as the communications interface between the sub-modules. Thus, the Filer ini tializes a workfile which the Editor uses to create a textfile which the Compiler uses to create a piece of a program which the Linker uses to create a runnable file which the eX(ecute command sets into operation. This sequence of events is controlled by the System commands. It is done "by hand", since the System was from the start conceived as an interactive environment. The point is that the System commands are what you must use to accomplish interaction between the various System components.
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Users' Manual System Commands
1I.l Promptlines
The promptline (sometimes called a menu) shows the command options at any given level of the System. Each command is invoked by a single letter -- 'E' for Edit,
's'
for Save, and so forth. Some things all promptlines have in common are:••• the name of the 'level' or System module at the beginning;
••• a list of available commands, with the calling letter capitalized and separated from the rest of the word by '(';
••• the version number of the program at the end of the line, in square brackets.
Here are a few representative promptlines:
Command: E(dit, R(un, F(ile, C(omp, L(ink, X(ecute, A(ssem, ? [IV.O]
Filer: G(et, S(ave, W(hat, N(ew, L(dir, R(em, C(hng, T(rans, OCate, Q(uit ?[A
>Edit: A(djust C(py O(lete F(ind l(nsrt J(mp R(place Q(uit X(chng Z(ap [E.6]
Anywhere in the p-System, a promptline will almost always be displayed at the top of the screen, and let you know what your options are. It is not always visible when you are using the Editor to insert text, and it is never visible while a user program is running. Typing unintelligible commands at any level may cause the promptline to go away; in this case, a space (' ') will cause the screen to be cleared and the correct promptline to be displayed.
Some promptlines include a '?'. There are often more commands than can fit onto one line, and typing '?' will display those commands. For example:
Filer: B(ad-blks, E(xt-dir, K(rnch, M(ake, P(refix, V(ols, X(amine, Z(ero
Users' Manual System Commands
••• and you type 'GRISWICH'<return>. The '.CODE' will be assumed.
You may have already seen the System promptline and screen as it appears after booting, and may have played with the System on your own or in conjunction with Ken Bowles' book. This is all the familiarity with promptlines that you need in order to start productively using the various Systemcohimands.
If y'ou are using a line-oriented terminal (such as a teletype), then you can set HAS SLOW TERMINAL to True in your SYSTEM.MISCINF'tj file; and the System will abbreviate most promptlines. If·· you have a CRT with narrow lines (less than 80 characters wide), then set SCREENWIDTH in SYSTEM.MISCINFO to the appropriate value. The System will display as much of a promptline as will fit on a line, and typing '?' causes it to display the remaining commands. Refer to the Installation Gu ide for details of modifying SYSTEM.MISCINFO with the SETUP utility.
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Users' Manual System Commands
1I.2 Disk Swapping
Since the IV.O Operating System does a good deal of swapping code segments into and out of main memory during the execution of a program, and since the user may change disks at various times (especially while running the System itself), the Operating System has various checks to aid disk handling, and reduce the possibility of error.
When a program requires a code segment that is on disk, and it is no longer on the disk in the drive from which it was originally read, the Operating System will display a prompt that looks something like this:
Segment not found on device II 5 Please replace volume USERI type <space> to continue
in this example, the System requests the disk USER 1:, and will wait until the user types <space>. (If the user types <space> but .has not replaced USER1:, the System will redisplay the prompt.)
If at any time during the execution of a program, a device is found to contain a v olu m e that the System did not expect, the System considers that device
"qu estionable" for the remainder of that program's execution. All subsequent reads and writes that the Operating System does to that device will check to see that the volume name is correct (provided the correct volume name is known). If the volume name is deemed incorrect, the System displays a prompt of the following sort:
Please replace volume USER2 in device II 5 type <space> to continue
in this case, the System expected the disk USER2:, did not find it, and therefore requested it.
These situations should not often arise, but will occur when a program requires
Users' Manual System Commands
11.3 Execution Option Strings
The eX(ecute command allows the user to specify some options that modify the System's environment. These include redirecting standard program
1/0
or standard System I/O, changing the default prefix (i.e., the volume name part of a filename;Users' Manual System Commands