MiniUnix/usr/doc/new/memo4

Find at most related files.
including files from this version of Unix. 
.NH
UNIX User Program Modifications
.PP
Since the MX system uses no segmentation unit, all
user programs must be compiled and relocated
to start at address 060000.
Under MX, the C programs are relocated automatically
using the 'ld' program which has been modified
as described below.
For assembly-language source programs, the 'a.out'
program may be relocated either using the 'reloc'
program or the 'ld' program.
The various user programs which have been modified
from the standard Version 6 UNIX or new programs
which are supported but not mentioned in the UNIX
Programmer's Manual (4) are described below.
.NH 2
ar
.LP
The archive program supported is a version which is updated
from that described in the UNIX Programmer's Manual.
It is written in the C language and has some new keys added.
However the documentation still applies.
.NH 2
bc
.LP
The 'bc' command works as in the standard UNIX system
but cannot be used interactively since pipes
are not implemented in the system.
In generating the source for 'bc' using the 'yacc'
compiler-compiler, the source must be edited slightly
to make it simulate the use of pipes.
.NH 2
check
.LP
The \fBcheck\fR program is not described in the UNIX Programmer's
Manual.
However, it combines most of the individual features of
\fBdcheck, icheck\fR and \fBncheck\fR as described in the manual.
A flag of \fI-l\fR will do the equivalent
of \fBncheck\fR with no flags.
All other flags described for \fBdcheck, icheck\fR and \fBncheck\fR
apply.
.NH 2
Debugger
.LP
The debugger \fBdb\fR has been slightly modified in order to ease debugging
under the MINI-UNIX system.  The default relocation address of all programs
is assumed to be 60000(8).  If the flag '-a' is given when the debugger
is invoked, the relocation address is assumed to be zero.  This is useful
for debugging the system.
.PP
The default address can be changed by editing 'db1.s' and setting the 
variable 'uorg' equal to the new relocation address.
Then the source code should be re-assembled.
If none of the changes are desired, the variable \fImx\fR in \fIdb1.s\fR
should be set to 0 and the source code re-assembled.
.NH 2
Kdmp
.LP
This program is used to extract a dump of the complete system (28K words)
from the swap area on disk.
The core image produced in the file "kore" may
then be debugged post-mortem.
Consult system source code for the actual disk tracks used.
If a system crash occurs and the core image of the system
is written out to disk, the system should be booted up
single-user.
Immediately, one should execute "kdmp" (preferably
on an uncorrupted file system) before the swap
area is over-written.
.NH 2
Ld
.LP
The \fBld\fR program has been modified to relocate the program
origin to 060000 automatically.
This is to facilitate the compilation of C programs
under the MINI-UNIX system.
Note that all assembly programs, after being assembled,
must be relocated to 060000 either by using the link
editor \fBld\fR or the relocation program \fBreloc\fR.
The relocation origin may be changed from 060000
by changing the value of the TOPSYS parameter
in \fIld.c\fR to the appropriate value.
.PP
Using the \fI'-a'\fR option flag with \fBld\fR turns
off the relocation of a program's origin.
The program is then assumed to start execution
at location 0.
This is useful for link editing the MINI-UNIX system itself
or any other program which starts execution at location 0.
.NH 2
Mkpt
.LP
The \fBmkpt\fR program constructs a prototype file
given a specification file for direct input to
the \fBmkfs\fR program.
Run "man 8 mkpt" for details.
.NH 2
Ps
.LP
The process status command outputs basically the same
information as that of the Version 6 UNIX \fBps\fR command.
It has been modified to take into consideration
the different process table layout and the different
swapping technique used in MINI-UNIX.
.NH 2
Reloc
.LP
This Program is used to relocate all relocatable symbols
in a program.
Thus "reloc a.out 60000" will relocate
all relocatable symbols in "a.out" and relocate the
starting address of the program (absolute zero)
to 060000.
It must be used with all assembler output programs
if the link-editor is not required.
.NH 2
Sh
.LP
Since the MINI-UNIX system does not support pipes, the shell has been
modified to simulate pipes through the use of disk files.  When a
command line which requires the use of a pipe is detected, a disk
file is created and opened for reading and writing.  The file is
immediately unlinked, so that the name is available for another pipe
right away.  The file is called '.__pf'.  Hopefully this name will
not conflict with any user file names.
Thus, the symbol '|' in a shell command line becomes equivalent to
\&'> .__pf ; < .__pf'.  The command:
.DS
	% prog1 | prog2
.DE
translates into:
.DS
	% prog1 > .__pf ; prog2 < .__pf
.DE
The process writing on the pipe writes everything into the file, and
when it exits, the reader process is swapped in.  It reads what the
writer has written on the pipe file.  The only danger in this type
of implementation is due to the limitation of space on the file system being used.
A very large amount of information going through a pipe could
fill up the disk.
Except for this, the pseudo-pipe code is transparent to the user.
.PP
The \fBsync\fR command has been added to the shell.
Thus the system call is made directly from the shell
and no other process is spawned.
.NH 2
Typo
.LP
This program checks for the most likely spelling errors
in a document.
It has been modified somewhat to enable it to fit
in 16K words of memory.
.NH 2
Yacc
.LP
The source for the \fByacc\fR compiler has been edited to change
some table sizes to make it run in 16K words of memory.
Further editing of symbols at the beginning of \fIy0.c\fR may be
required to make up a \fByacc\fR compiler with different
table sizes for a particular application.