The Programmer's Guide to TRSDOS Version 6 - Tim Mann's Home ...

7.6.57 @OPEN SVC-59
This SVC will open an existing file or device. The Logical Record Length (LRL) passed in
register B should match the LRL stored in the directory. If it does not, an "LRL open
fault" error will be returned; however, the file will still be opened. If the file is
already in an open state, the file's directory record will indicate the condition. In
this case, the file will still be opened; however, only READ access (or less depending on
the access permitted by the password) will be granted. A "File already open" error will
also be returned.
Registers Affected: AF.
Entry:
HL A pointer to your buffer for disk I/O.
DE A pointer to the File or Device Control Block containing the filespec or
devicespec.
B Should contain the Logical Record Length for the open file.
Exit:
A Error return code
Z Set if open was successful
7.6.58 @PARAM SVC-17
This SVC can be used to parse an optional command line parameter string. Its primary
function is to parse command parameters contained in a command line totally enclosed
within parentheses. The parameter formats acceptable for the command line entries are as
follows:
PARM=X'hhhh' hexadecimal entry
PARM=ddddd decimal entry
PARM="string" alphanumeric entry
PARM=ON switch entry indicating TRUE
PARM=YES switch entry indicating TRUE
PARM=Yswitch entry indicating TRUE
PARM=OFF switch entry indicating FALSE
PARM=NO switch entry indicating FALSE
PARM=N switch entry indicating FALSE
The user-entered parameters that are to be accepted by your application are contained in
a parameter table (PRMTBL$). This table stores the parameter names and a pointer to
indicate where the user response is to be placed. Two forms of the PRMTBL$ are supported.
The first form uses a fixed width table with a maximum name length of six characters. The
PRMTBL$ is coded as follows. A 6-character NAME left justified and filled with blanks
followed by a 2-byte address VECTOR which points to the location which will receive the
parsed values. The 2-byte memory address denoted by the address VECTOR field of your
table receives the value of PARM if PARM is non-string. If a string is entered, the 2byte
memory address receives the address of the first byte of "string". NAME and VECTOR
may be repeated for as many parameters as are desired. A byte of X'00' must be placed at
the end of the table to indicate its ending point.
The second PRMTBL$ format permits a greater degree of flexibility in parameter handling.
It also provides feedback as to each parameter entered by the user. Its format begins
with a byte of X'80' to indicate the enhanced table. Each parameter is then identified
with four fields. These fields are as follows:
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