SEXEC

Syntax

SEXEC device_file,start,length,data or

SEXEC device_file,start[,length[,data[,extra[,type]]] (Minerva v1.80+) or

SEXEC [device_]file,start,length,data (Toolkit II) or

SEXEC #channel,start,length,data (SMS only)

Location QL ROM, Toolkit II

In order for a program to be stored as an executable Job, it is necessary to store the machine code in a specified format on disk. The command SEXEC allows you to do this, taking a specified amount of code from memory and storing it in the specified file in a form which can later be EXECuted.

You will need to specify the start address of the machine code, the length of the code to be stored and the amount of data space to be given to the program when it is loaded back into memory (the data space represents the amount of working memory which is linked with the program when it is loaded, either for storing data at the end of the program or for the user stack - see a good QL machine code book for more details). The specified file name must include the name of the device to be used, unless Toolkit II is present, in which case the default program device is supported. If Toolkit II is present and the file already exists, you will be given the option of overwriting the file.

Example

To amend a given executable program, you may need to do the following:

100 length=FLEN(\example_exe)
110 datasp=FDAT(\example_exe)
120 start=RESPR(length)
130 LBYTES example_exe, start
140 POKE start + 1024, 100
150 SEXEC flp1_example_exe, start, length, datasp

NOTE 1

On Minerva ROMs (pre v1.80), if SEXEC was aborted for some reason whilst writing to a file, the file would be deleted. On later versions of Minerva and all other QL ROMs, the incomplete file is kept. Toolkit II reports Medium Full if this is the case.

NOTE 2

The Minerva variant is overwritten by the Toolkit II version of this command.

NOTE 3

On Minerva pre v1.83, SEXEC set the wrong file type!

MINERVA NOTE

On Minerva v1.80 (or later) the command SEXEC is practically the same as SBYTES. The only difference is the type parameter which defaults to 1 as opposed to 0 with SBYTES.

SMS NOTE

The fourth variant of this command allows you to save the data to an already existing channel which is OPEN to a file, thus cutting down on the number of times you need to access the file for error trapping (for example). See SBYTES for an example.

WARNING

Saving part of the QL’s memory with SEXEC does not make it into EXECutable code - you must ensure that the program concerned has a proper Job header and conforms with the normal QDOS rules for EXECutable programs.

CROSS-REFERENCE

SEXEC_O is very similar. EXEC and EXEC_W allow you to load a program saved with SEXEC.