INT 21,29 - Parse a Filename for FCB

AH = 29h

AL = bit pattern to control parsing (see bit meanings below)

DS:SI = pointer to a filespec to parse

ES:DI = pointer to a buffer for unopened ~FCB~

Bit patterns for parsing control found in AL:

¦7¦6¦5¦4¦3¦2¦1¦0¦ AL

¦ ¦ ¦ ¦ ¦ ¦ ¦ +---- 1 = ignore leading separators

¦ ¦ ¦ ¦ ¦ ¦ ¦ 0 = don't ignore leading separators

¦ ¦ ¦ ¦ ¦ ¦ +----- 1 = modify drive ID if specified

¦ ¦ ¦ ¦ ¦ ¦ 0 = modify drive ID regardless

¦ ¦ ¦ ¦ ¦ +------ 1 = modify filename if specified

¦ ¦ ¦ ¦ ¦ 0 = modify filename regardless

¦ ¦ ¦ ¦ +------- 1 = modify extension if specified

¦ ¦ ¦ ¦ 0 = modify extension regardless

+-------------- unused

on return:

AL = 00 if no wildcard characters present

= 01 if wildcards present in string

= FF if drive specifier is invalid

DS:SI = pointer to the first character after parsed filename

ES:DI = pointer to the updated unopened FCB

- retrieves filename from the command line string and places

the filename components into an unopened FCB for later use

- if no filename is found a pointer is returned in ES:DI that

has a blank at ES:DI+1

- this function can be used to detect the existence of logical DOS

drives by creating a dummy filespec with a drive letter and colon

prepended. If the drive is invalid, this function will return FF

in AL