When Microsoft Corp. introduces a new version of MS-DOS tomorrow, it will be a welcome upgrade that goes a long way toward lifting the decade-long curse on the operating system software that controls tens of millions of IBM PC and compatible computers worldwide.
The curse, which limits the main working memory of MS-DOS to 640 kilobytes, was created by Microsoft and IBM when they collaborated on the original IBM PC in 1981. Back then, 640 kilobytes seemed like more memory than anyone would ever use, since it was 10 times the amount available for the original PC.
Most personal computers sold today use microprocessors capable of working with megabytes (millions of bytes, or characters) of memory instead of kilobytes (thousands of characters), and many software applications have grown so complex they need a shoehorn to fit into 640 kilobytes.
If the user tries to squeeze one of these pudgy applications into the 640 kilobytes of working memory along with a hefty data file and other standard software, the DOS curse causes the PC to choke.
The new version, MS-DOS 5.0, is still constrained by the 640-kilobyte limit, but the streamlined new version frees more of the working space to the user. This is good news for any DOS user who has ever faced a "not enough memory" message.
Of course, users might still run out of memory even if they do upgrade to MS-DOS 5.0, but it is less likely.
The MS-DOS 5.0 upgrade package, for people who already own a version of DOS, is available from Microsoft's usual dealers for a list price of $99.95, which will probably be discounted to $75 or less. If you have difficulty finding an upgrade package, call Microsoft at (800) 992-3675.
There are other advantages to upgrading to MS-DOS 5.0 besides superior memory management. MS-DOS 5.0 has new utility commands, including "undelete" and "unformat," which allow the user to restore files that have been accidentally erased. Microsoft acquired these two very handy features from Central Point Software, maker of the popular PC Tools utility programs.
MS-DOS 5.0 also puts a stake through the heart of EDLIN, the annoying and obtuse line editor that earlier versions of DOS provided for entering and editing simple files. In its place is a full-screen text editor, more like a simple word processor.
There is a new "shell," a graphical mask that fits over the regular DOS screens and supposedly makes DOS easier to use. Instead of typing the familiar DOS commands, the shell user can manipulate DOS files by using a mouse to point at and click on icons. The new MS-DOS shell is essentially a subset of Microsoft's more robust Windows operating system.
NB The shell includes an important feature called task switching,
borrowed from Windows, which lets users switch from one application to another by clicking the mouse or pressing a designated key on the keyboard.
Without task switching, the DOS user has to exit the current application before loading the new one.
Not least, Microsoft appears to have tested this version exhaustively before releasing it. MS-DOS 5.0, according to the company, has been tested by more than 7,000 individual and business users since the start of the year, ensuring that it does not cause problems or contain any glitches that might jeopardize a user's data.
The extra precautions were the result of Microsoft's earlier blunder in releasing a buggy version of MS-DOS 4.0. The company clearly did not want to repeat that mistake.
As added insurance, the installation procedure for the MS-DOS 5.0 upgrade has a pair of fail-safe mechanisms.
The setup program prompts the user to make a current backup copy of the computer's hard disk before installation (be sure to have a couple of boxes of floppy diskettes handy). MS-DOS 5.0's built-in backup program is fairly slow and crude, at least when contrasted with other commercial backup programs, but it is convenient.
Further, the setup program creates an "uninstall" disk that contains copies of the user's current
DOS files. If anything goes wrong, the uninstall disk restores the system to its condition before MS-DOS 5.0 was installed.
"It's an absolutely fantastic product," said Gordon Eubanks, chief executive of Symantec Inc., a California software company that publishes the Norton Utilities for DOS. A new version of the Norton Utilities, as well as a new version of Central Point Software's PC Tools Deluxe, work especially well with MS-DOS 5.0 and will be discussed in this column next week.
For most people, memory management is the key feature of MS-DOS 5.0. Assuming the PC is based on a 286 (IBM PC-AT or compatible) or newer processor, the streamlined MS-DOS 5.0 takes up at least 45 kilobytes less space than earlier DOS versions.
Even more conventional memory can be freed on machines based on a 386, 386SX or i486 chip. During the installation process, the MS-DOS 5.0 upgrade scans the system to see if it can load all but about 18 kilobytes of itself into the memory space between 640 kilobytes and 1 megabyte, which have been off limits to DOS before this.
MS-DOS 5.0's smart installation system also tracks down assorted other programs -- like mouse drivers, network drivers and pop-up programs -- and tries to stuff them in the memory attic as well. The result is more working space for word processors, spreadsheets and other application programs.