Compatibility: 2.0+
Expects: AX    4b01H
DS:DX address of an ASCIIZ  filespec of the program to load
ES:BX address of an ExecLoadRec
                                                                  
Returns: AX    error code if CF is set to CY
ES:BX some information is returned in the ExecLoadRec
                                                                  
Info: This allocates memory and loads a program.  It builds a PSP and
performs all needed segment fixups in preparation for executing
the code, but does not actually begin execution.

DS:DX points to an ASCIIZ string in the form...
d:\path\filename.ext 0 
If the drive or path is omitted, defaults are assumed.

ES:BX points to a block of memory prepared as an ExecLoadRec that has
been filled with the information needed, similar to the needs of
fn 4b00H (exec).

On return the ExecLoadRec contains the required entry point
(lCsIp) and stack address (lSsSp) to use when starting the
program.

Notes:   There must be enough free memory for DOS to load the program.

See Also: Fn 4b00H (execute program)
Fn 4b03H (load overlay)
Fn 4b05H (set execution state)
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DOS Fn 4b01H: Load Program