typedef enum {
FR_OK = 0,              /* (0) Succeeded */
FR_DISK_ERR,            /* (1) A hard error occurred in the low level disk I/O layer */
FR_INT_ERR,             /* (2) Assertion failed */
FR_NOT_READY,           /* (3) The physical drive cannot work */
FR_NO_FILE,             /* (4) Could not find the file */
FR_NO_PATH,             /* (5) Could not find the path */
FR_INVALID_NAME,        /* (6) The path name format is invalid */
FR_DENIED,              /* (7) Access denied due to prohibited access or directory full */
FR_EXIST,               /* (8) Access denied due to prohibited access */
FR_INVALID_OBJECT,      /* (9) The file/directory object is invalid */
FR_WRITE_PROTECTED,     /* (10) The physical drive is write protected */
FR_INVALID_DRIVE,       /* (11) The logical drive number is invalid */
FR_NOT_ENABLED,         /* (12) The volume has no work area */
FR_NO_FILESYSTEM,       /* (13) There is no valid FAT volume */
FR_MKFS_ABORTED,        /* (14) The f_mkfs() aborted due to any problem */
FR_TIMEOUT,             /* (15) Could not get a grant to access the volume within defined period */
FR_LOCKED,              /* (16) The operation is rejected according to the file sharing policy */
FR_NOT_ENOUGH_CORE,     /* (17) LFN working buffer could not be allocated */
FR_TOO_MANY_OPEN_FILES, /* (18) Number of open files > FF_FS_LOCK */
FR_INVALID_PARAMETER    /* (19) Given parameter is invalid */
} FRESULT;

me@myhost:~/mmbasic-c-development/cmm2 $ grep --recursive MMerrno *
Inc/MMBasic.h:extern int MMerrno;
Src/FileIO.c:    MMerrno = e;
Src/Functions.c:    iret = MMerrno;
Src/MM_Misc.c:    iret = MMerrno;
Src/MMBasic.c:    if(MMerrno == 0) MMerrno = 16;                 // indicate an error
Src/Commands.c:int MMerrno;                                      // the error number
Src/Commands.c:        MMerrno = 0;                              // clear the error flags

errText$(1) ="No SD card found"
errText$(2) ="SD card is write protected"
errText$(3) ="Not enough space"
errText$(4) ="All root directory entries are taken"
errText$(5) ="Invalid filename"
errText$(6) ="Cannot find file"
errText$(7) ="Cannot find directory"
errText$(8) ="File is read only"
errText$(9) ="Cannot open file"
errText$(10)="Error reading from file"
errText$(11)="Error writing to file"
errText$(12)="Not a file"
errText$(13)="Not a directory"
errText$(14)="Directory not empty"
errText$(15)="Hardware error accessing the storage media"
errText$(16)="Flash memory write failure"
errText$(17)="Source and destination are the same!" 'MMBasic bug