Copyright © 1988 R.D. Eager
Permission is granted to copy and/or modify this document for private use only. Machine readable versions must not be placed on public web sites or FTP sites, or otherwise made generally accessible in an electronic form. Instead, please provide a link to the original document on the official ML/I web site.
This implementation of ML/I contains all the features described in the ML/I User's Manual, Fifth Edition, including New Features 1 to 6 as described in that manual.
This implementation is a 16 bit DOS program; as such, it will run on even the most basic PC, with an 8086 or 8088 processor.
The call of ML/I takes the form
ml1 input1,input2,input3 output1,output2,listing,debuggingfile
The parameters have the following meanings:
CON: is used.
CON: is used.
CON: is used.
All output files must be different, and they must also be different from any of the input files. Any legal DOS file or device name may be specified for any file.
Any attempt to use an input file (except input1) not specified in the call of ML/I will cause the process to be aborted, after the output of a suitable message.
ml1
This is sufficient for working through the Simple Introductory Guide.
PIG.TXT and DOG.ASM, and
output to FOO.DAT, with listing to BAZ.LST:
ml1 pig.txt,dog.asm foo.dat,,baz.lst
Input may be taken from any one of the input files (or
streams, as they will be referred to from now on). The value
of S10 controls the selection. The possible values are:
S10 = 1
S10 = 2
S10 = 3
If S10 is set to zero, ML/I treats this as "end of file" and
ceases processing. If S10 is set to any illegal value (negative,
greater than three, or a value between one and three associated
with an input stream which has not been specified) then the
process is aborted.
If a change of input stream is made, the original stream is not
"forgotten". Any attempt to read from this stream again will
cause ML/I to carry on where it left off. When the end of an
input stream is reached, ML/I checks to see if it is the
revert stream. If it is, the process is terminated; otherwise
input is switched to the revert stream, and processing continues.
The revert stream is initially 1; its value is held in S23 and
may be altered by the user if required.
It is possible to designate that one character be translated to another on input. This makes it possible to input a character that a device does not support. However, only one character code can be translated in this way.
If it is desired to perform a translation, S16 should be set to the
ASCII code of the character to be translated,
and S17 to the ASCII code of the character that is to
replace it. For example, if % (ASCII 37) was to represent a tab
(ASCII 9), S16 and S17 should be set in the
following way:
MCSET S16 = 37 MCSET S17 = 9
Initially, S16 has the value -1,
which since it does not correspond
to a valid internal code, will not cause any translations to be made.
The ordering of input operations is as follows:
S10 equal to zero.
S10.
S16 and S17.
Output may be directed to either, both or neither of the primary
output and the secondary output. The values of S21 and S22
control the selection; S21 controls the primary output,
and S22 controls the secondary output.
In both cases, a value of 0 means that no output is to take place,
and a value of 1 means that output is to take place.
A listing of the output from ML/I may be directed to the listing
output file specified in the call of ML/I. Listing is controlled
by the value of S20. If S20 is zero, no listing is produced at
all. If S20 is one, a listing without line numbers is generated;
if S20 is two, line numbers are included in the listing. S20 has
an initial value of zero.
The character set used by ML/I is 7-bit ASCII (codes from 0 to 127 decimal). However, the character code 26 decimal (1A hexadecimal) is used internally to indicate end of file, and will cause unpredictable effects if it appears in the input to ML/I.
Error messages are output to the debugging file specified in the
call of ML/I; this defaults to CON:.
With reference to Chapter 6 of the ML/I User's Manual,
the number 2N (the maximum number of characters inserted into an
error message without truncation) is 64.
The error character is question mark (?).
At the end of a process, a message of the form
At end of process: N lines, M calls
is output to the debugging file.
All files are opened as soon as ML/I is entered. Failure to open any file causes an appropriate message to be output, and ML/I immediately exits.
The following run-time messages are peculiar to this implementation.
Message
S10 has illegal value, viz n
Description
S10has been set to the value n, which is either outside the range 0-3, or is associated with an input stream that was not specified in the call of ML/I. Note that this error may be caused byS23(the revert stream) being set to an illegal value, and end of file then being reached on another input stream.
System Action
The current process is aborted.
Message
Primary output failure
Description
An error has occurred while writing to the primary output file.
System Action
The current process is aborted.
Message
Secondary output failure
Description
An error has occurred while writing to the secondary output file.
System Action
The current process is aborted.
Message
Listing output failure
Description
An error has occurred while writing to the listing file.
System Action
The current process is aborted.
Message
Debugging file output failure
Description
An error has occurred while writing to the debugging file.
System Action
The current process is aborted.
The initial environment contains ten permanent variables, all set to zero. All integers in, or derived from, macro expressions should be less than 32767 in magnitude. Overflow is not detected, except in the case of division by zero, and its effect is undefined.
The following are the layout keywords for this implementation:
SPACE | meaning a space.
|
NL | meaning a newline.
|
TAB | meaning a tab.
|
SL | meaning the imaginary startline character.
|
SPACES | meaning a sequence of one or more spaces.
|
There are 24 system variables. S1 to S9 are independent of the
implementation, and are used to control and monitor ML/I itself.
S10 to S23 are implementation dependent,
and are used to control input/output, etc.
If an S-variable is set to any value other than those given below,
the effect is undefined (except for invalid values of S10,
which always cause the process to be terminated).
S1-S9S1
S1 is one, the imaginary startline
character is inserted on input. If S1 is zero, no startlines are
inserted; this is the initial setting.
S2
S2; it may be changed at any time.
S3
S3 is one, the error message normally
generated if a warning marker is not followed by a macro name is
suppressed. If S3 is zero (the initial value), the message is
produced.
S4
S4 is one, the context print-out
normally given after a call of MCNOTE is suppressed. If
S4 is zero, the context print-out is given; this is the initial
setting.
S5
S6
S7
S8
S9
S10-S26S10
S10 is
one.
S11
S12
S13
S14
S15
S16
S16 are translated to characters with the code given by
S17, on input. Initially S16 is -1, so no
translations are performed.
S17
S16 above.
S18
S19
S19,
and is updated when the first character is output to each new
line. It may be changed if desired.
S20
S20 controls output to the listing file.
See Section U.2.5 for details.
S21
S21 controls output to the primary output
stream, and is initially set to one. See Section U.2.4 for details.
S22
S22 controls output to the secondary output
stream, and is initially set to zero. See Section U.2.4 for details.
S23
S23 contains the current revert stream. See Section U.2.3 for
details.
S24
S24 contains the number of bytes of macro storage and workspace
available in this version of ML/I.