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.foDSIdCAT - Olympia Page # .UJ1 .cw10 DSI dCAT - DISK CATALOG PROGRAM in dBASE III by P. L. Olympia, Ph.D. Sysop, SMUG RBBS, 301-963-5249 Users of dBASE II who for years have had to program around its many limitations are smiling these days - dBASE III has arrived and with it the computing power that everyone had been clamoring for. It is a tribute to the versatility of dBASE III that it took very little time, not too mention very little code, for us to convert many of our application programs and utilities from traditional programming languages to dBASE III. Two of our most heavily used programs that we converted within a week of dBASE III's arrival were an appointment calendar generator (originally written in "C") and a disk cataloging system (originally written in assembler). This article describes DSI dCAT, a subset of our disk cataloging system that is hereby being released to the public domain. The article is also partly a tutorial on the new features of dBASE III. DSI dCAT IN A NUTSHELL The system allows one to maintain a catalog of files contained on either floppy or fixed disks. Files contained on the disk's subdirectory (excluding the . and .. "files") will also be read and cataloged. Since the system was originally conceived to track diskette files, it is presently set to handle up to nine subdirectories on a given disk but not subdirectories within subdirectories. The system has a user-maintained data base of "exclude" filenames; these are files which will be excluded from the catalog if they are found on a disk's directory. Typical examples of such files are COMMAND.COM and AUTOEXEC.BAT which are usually found on multiple diskettes and are of no real interest to a catalog system. The number of files that may be cataloged is one billion - a dBASE III limitation that we cannot confirm. The system consists of two command files: (1) DSIDCAT.PRG is the main driver program that handles the user interface including the main menu, help, data edits and reports; (2) DSIREAD.PRG is the heart of the system that takes care of reading the disk directory and loading the data bases with information obtained from the directory. DSIREAD.PRG makes full use of dBASE III's power and is described in detail below. .cp7 DATA BASES USED dBASE III allows multiple data bases to be open at one time and the catalog program takes advantage of that. The four data bases that the system uses are: 1. DSIFILE.DBF - data base of cataloged filenames and related data INDEX: Indexed on FILE to DSIFILE STRUCTURE: Field Field name Type Width Dec Description ----- ---------- --------- ----- ----- -------------- 1 FILE Character 12 File Name 2 FBYTES Numeric 6 Number of bytes 3 FDATE Date 8 Creation date 4 FTIME Character 6 Creation time 5 DISK Character 23 Disk label 6 FCATEG Character 30 Category 7 FDESC Character 50 File Description ** Total ** 136 NOTE: FCATEG and FDESC are added by the user via the EDIT function 2. DSIDISK.DBF - data base of cataloged disks INDEX: Indexed on DISK to DSIDISK STRUCTURE: Field Field name Type Width Dec Description ----- ---------- --------- ----- ----- -------------- 1 DISK Character 23 Disk label 2 NUMFILES Numeric 5 No. files 3 BYTESFREE Numeric 7 Bytes free 4 BYTESUSED Numeric 7 Bytes used ** Total ** 43 3. DSIXCLUD.DBF - data base of filenames to be excluded INDEX: Indexed on FILE to DSIXCLUD STRUCTURE: Field Field name Type Width Dec Description ----- ---------- --------- ----- ----- -------------- 1 FILE Character 12 File name ** Total ** 13 .cp10 4. DSISCRAT.DBF - scratch data base loaded from redirected output of the DOS DIR command INDEX: None STRUCTURE: Field Field name Type Width Dec Description ----- ---------- --------- ----- ----- -------------- 1 FNAME Character 8 2 FILL1 Character 1 3 FTYPE Character 3 4 FILL2 Character 3 5 FBYTES Character 6 6 FILL3 Character 2 7 FDATE Character 8 8 FILL4 Character 2 9 FTIME Character 6 ** Total ** 40 THE SYSTEM IN DETAIL Figure 1 shows the source code for the main driver program, DSIDCAT.PRG. The DO WHILE .F. - ENDDO block at the beginning of the program shows a technique for including a cluster of comment lines in a dBASE III program without using an asterisk on each line. The SET SAFE OFF statement prevents dBASE III from asking the user for permission to overwrite DSISCRAT.DBF each time a new disk to be cataloged is read from the designated drive. Two of the memory variables declared public are MDISK (drive where disk to be cataloged is to be mounted) and MDIR (file to hold the redirected output of the DOS DIR command). These variables are passed to DSIREAD.PRG; their values may be changed by the user from a main menu option. The program begins by asking the user for the drive containing the system files and programs. This allows for more than one catalog of files to be maintained on different drives or diskettes. The system's main menu is shown in Figure 2. I created the screen using WordStar and then used dBASE III's dFORMAT program to convert it to an FMT file. I then used WordStar's read file command (^KR) to include the FMT file in the main program, DSIDCAT.PRG. A brief explanation of menu choices is provided if the user picks the H(elp) option. The explanation is shown in the source listing and will not be repeated here. However, the Z(ap) and V(iew) options introduce new concepts and are worth discussing. The ZAP command of dBASE III is an efficient (and dangerous) way of removing data base records. Its equivalent in dBASE II is the notoriously slow DELETE ALL and PACK commands. The V(iew)/Change Report Destination option assigns either a space to the memory variable MPRSC if the user elects the screen to be the report destination, or the string 'TO PRINT NOEJECT' if she elects instead to route the report to a printer. With this technique, we save a lot of coding just to generate a report. Note that under the F)ind A File option, we only had to use the statement: REPO FORM DSIFILE FOR '&MFILEN'$FILE &MPRSC instead of a more cumbersome alternative such as: IF PRINTER REPO FORM DSIFILE FOR '&MFILEN'$FILE TO PRINT NOEJECT ELSE REPO FORM DSIFILE FOR '&MFILEN'$FILE ENDIF Another technique that the program uses can be seen under the D(elete) a Diskname option. In dBASE III, values of logical variables require the surrounding periods as in .T. or .F. Thus, the old dBASE II code that goes something like this: STORE Y TO MORE DO WHIL MORE ... INPUT 'Delete another diskname? (Y/N)' TO MORE ENDDO while more is fraught with danger of generating a syntax error unless the user always remembers to respond with .Y. instead of just Y (or .N. instead of N). We avoid that problem by replacing the INPUT statement with the following: WAIT 'Delete another diskname? (Y/N)' TO ok STORE ok$'yY' TO more The last statement performs the same work as the following five statements: IF ok$'yY' STORE .T. TO more ELSE STORE .F. TO more ENDIF The program also takes advantage of two new and desirable features in dBASE III, namely EXIT (to exit from a DO WHILE construct) and SEEK (a superior alternative to FIND). SEEK allows an expression to be its argument, so that it is completely valid to have the name of a memory variable (instead of its value) as the argument. We can say, for example, SEEK mvar while we can only say something like: FIND &mvar Although Ashton-Tate warns dBASE III users not to use macros inside loop constructs such as DO-ENDDO and IF-ENDIF (the claim is that the speed of execution may be degraded up to 30 percent) we use macros with impunity because we really do not have any choice - all our programs are in one giant DO WHILE .T. loop. If there is any speed degradation, we never observed it. To anyone who has used dBASE II as long as we have, even a snail looks fast and, besides, dBASE III is just light years ahead of dBASE II in speed. Finally, the program contains four statements that use the new SPACE function to assign a fixed number of blanks (spaces) to memory variables. The function saves us the trouble of counting (or miscounting) spaces to assign the variables. HOW IT IS REALLY DONE The A(dd) New Disk to Catalog option of the main menu invokes the command file, DSIREAD.PRG where all the hard work is done. We get an idea of some of dBASE III's power by examining the source listing in Figure 3. dBASE III has DOS-like commands such as TYPE. More importantly, it allows us to invoke any DOS program from within it (provided that we have enough memory for both dBASE and the external program). The approach used by the program is to read a disk directory using the DOS DIR command and redirect the output of the command to a scratch file defined by the memory variable MDIR. The actual dBASE III command that does this is: RUN DIR &mdisk.*.* >&mdir The period after '&mdisk' is important because the macro is at the beginning of a "word" instead of at its end. Assuming that MDISK='B:' and MDIR='D:DIRSCRAT.TXT', the macro expansion produces the command: RUN DIR B:*.* >D:DIRSCRAT.TXT The program then decomposes the standard output of the DIR command into a form suitable for APPENDing to DSISCRAT.DBF. It also determines if the disk has a volume ID; if there is no volume ID, the second line will have the string 'no label'. In that case, the program asks the user for a disk volume label and places it on the disk header by way of an external program, CLIP.COM - a public domain program written by W.C. Bodycomb. CLIP.COM (or a similar program such as Norton's LABEL.COM) need not be on the current directory if the proper path has been set to enable DOS to find it. If the volume label has been encountered before, the user has the choice of replacing the old entry with the current one or continuing with a different disk. The program recognizes that a "file" is a subdirectory when it encounters the string '<DIR>' in DIR's output line. It keeps track of all subdirectories (up to 9 on a given disk) that it has encountered and reads the files of those subdirectories by invoking the CD and DIR commands as before. While the DOS DIR command only gives the number of available bytes on the disk, the program also computes the number of bytes that have been used . Both values are stored in the second data base, DSIDISK.DBF. We have used this system to catalog more than 4000 files on diskettes with multiple subdirectories. Clearly, the best performance is obtained if the system files are on a hard or RAM disk. Copies of the entire system along with CLIP.COM are available free from the SUGI SIG/M RBBS (see below for the phone number). You will need a PC communications program that support the XMODEM protocol. Those without one can get a starter communications program, with instructions, also from the RBBS. FIGURE 2. DSIDCAT MAIN MENU DSI dCAT MAIN MENU Today: 07/20/84 ------------------------------------------------------------------------ SETUP S) Set Environment Z) Zap/Erase all catalog entries V) View/Change report destination DATA ENTRY/EDIT A) Add or Read a new disk to catalog E) Edit a filename record D) Delete/List diskname record(s) I) Add a filename to the EXCLUDE file REPORTS F) Find a filename in the catalog L) List all files on a given disk OTHER H) Help with these choices X) Exit this program Please choose a letter ... : :