Types of executable files A file whose name ends in ‘ .xrel ’ is a relocatable MC68000 machine language program. It is designed to be loaded into memory and executed. A file whose name ends in ‘ .shell ’ is a text file (created with edit ) containing a list of commands which 1616/OS interprets when the shell file is executed. .exec ’ file is non-relocatable MC68000 machine language. It is loaded at a specific, fixed address in memory for execution. If this particular memory is not freethe exec program cannot be executed, so you should only use .exec programs sparingly. They are really an obsolete form of program.
In general xrel files are preferable to exec files because multiple programs can reside in memory when they are relocatable. exec files are used during program development and debugging or for special applications; they are partially a relic fromearlier versionsof 1616/OS , and maynot be available infutureversions. Please note that you must have Version 3 or later of the operating system to use xrel files, and that almost all programs produced are in xrel format. Executing binary files When you execute a binary program from an .xrel or .exec file it is loaded into memory and executed.
If it is an exec file it is loaded at the start address indicated by its ‘load address’ attribute (the third column in the display). If it is an xrel file it is loaded at the highest available address where it will fit. If the ‘load address’ is unsuitable, or the program will not fit into available memory, an error message is displayed and the program is not run. The contents of the command line are passed to the loaded program so that you may supply it with any options, file names, etcetera which it may need. This is how‘arguments’are passedalongto programs,and why mostprogramsare written to accept command line arguments.
If the program is correctly written, then any output which it normally produces upon the screen may be redirected to devices or disk files by using the ‘>’ or ‘>>’ constructonthecommand line. Any keyboardinput maybe obtained from adevice or a disk file by using the ‘ Error messages or other special output may be redirected to devices or files with the ‘}’ or ‘}}’ constructs. When the program has ended it returns control to 1616/OS ’s command interpreter. There is much more about this topic in the Programmer’s Manual , the Technical Reference Manual , and the Assembler Manual . Page 40 User Tutorial Manual Starting Programs