China DOS Union

Understanding of the setramd.bat command line. If there are any mistakes, please correct them, masters!

@echo off
a:\findramd
:: Run findramd in drive a to find the virtual drive.
if errorlevel 255 goto no_ramdrive
:: If the return value of executing findramd is 255, it means there is no virtual drive. Then execute no_ramdrive to display the information that the virtual drive does not exist.
if not errorlevel 3 goto no_ramdrive
:: If the return value of executing findramd is not 3 (when the return value is 3, the virtual drive exists), it means there is no virtual drive. Then execute no_ramdrive to display the information that the virtual drive does not exist.
goto do_shift
:: If the above two situations do not hold (indicating that the virtual drive exists), then execute do_shift to start setting the drive letter of the virtual drive.

:loop
:: Determine the drive letter of the virtual drive.
if errorlevel %1 goto no_shift
:: Because after shift is executed, the return value is the value represented by parameter %1. If the value represented by parameter %1 can be returned as the return value, it means that parameter %1 is not empty. Then execute no_shift to assign a drive letter to the virtual drive.

:do_shift
:: Start setting the drive letter of the virtual drive.
set cdrom=%2
:: Set the string cdrom (the drive letter of the CD-ROM. Determined by mscdex /L:%cdrom%) corresponding to parameter %2. Please note: At this time, the drive letter assigned to the CD-ROM is determined by the hardware and does not include the virtual drive established by ramdrive. Because the default drive letter allocation of the system is: floppy drive (a), floppy drive (b), hard disk, CD-ROM. So, if there is only one partition on the hard disk, the hard disk (c), CD-ROM (d). If there are multiple partitions on the hard disk, the CD-ROM drive letter is pushed back. If there is no hard disk, the CD-ROM (c). When there is a virtual drive, the virtual drive is arranged between the hard disk and the CD-ROM, so the CD-ROM drive letter will be moved back by one position.
shift
:: Shift the parameters by one position to the left (that is, make the drive letters corresponding to parameters %1 and %2 move forward by one position).
shift
:: Shift the parameters by one position to the left (that is, make the drive letters corresponding to parameters %1 and %2 move forward by one position again).
if not %1*==* goto loop
:: After two left shifts, if parameter %1 is still not empty (that is, %1*==* is not established), it means the virtual drive exists. Then execute loop to determine the drive letter of the virtual drive.
goto no_ramdrive
:: After two left shifts, if parameter %1 is empty (that is, %1*==* is established), it means the virtual drive does not exist. Then execute no_ramdrive to display the information that the virtual drive does not exist.

:no_shift
:: Assign a drive letter to the virtual drive.
set ramd=%2
:: Let the drive letter of the virtual drive take the drive letter corresponding to parameter %2 (that is, the drive letter that the CD-ROM obtained before the virtual drive was established).
goto success
:: Execute success to display the information that the virtual drive is successfully established.

:no_ramdrive
:: No virtual drive exists or cannot be established (some prompt information can be set).

:success
:: Display the information that the virtual drive is successfully established

Thank you, the original poster!
Some questions that I didn't understand before are now clear after the original poster's explanation.
Thank you here!

Thanks to the LZ, I've gained new knowledge again, heh heh. Hope there'll be more next time.

Popular science knowledge lecture~ I like it!

Thanks

The benefits of searching old posts, well, thank you for the楼主's sharing.

（注：“楼主”是中文特定词汇，在英文中通常保留拼音“lz”或直接使用“the poster of the thread”，但根据要求如果不翻译则保留原文，这里原句中“楼主”未翻译，整体按照要求翻译为上述内容）