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PMAP 2.10 --------- PMAP (Program MAP) displays how your PC's memory is being used. It lists all active programs (including resident programs such as Sidekick and PCED), displays free memory areas and their locations, identifies device drivers, summarizes expanded (EMS) and extended (XMS) memory use, and details certain DOS data areas. Version 2.10 adds support for XMS (extended memory) and the HMA (high memory area). We have found that the old switch syntax was becoming unworkable (PMAP was designed in the good old days when memory was memory), so we decided to bite the bullet and change the way some of the options work. Some switches have been renamed to conform with current terminology (/X was for expanded memory, is now for XMS memory) and some usage has been changed. For example, /S used to mean "display ONLY standard memory"; no, it means "display standard memory in addition to anything else that's selected." We apologize to anyone who has to change batch files, etc., but we felt that the changes were necessary. | identifies information about new features for PMAP 2.0. Syntax summary -------------- The command line syntax of PMAP is: pmap [program-list] [/options] The default behavior, if no arguments are supplied, is: PMAP /e /s /x (or, yes, PMAP /sex) The program-list, if present, restricts the display of resident programs to those listed; the list may include wildcards (*). The program list affects the standard memory display only. See "Standard memory display", below. | The option switches are: | | Select primary displays(s): | /e display expanded (EMS) memory summary | /k display data area of DOS kernel (DOS 3.0 or later) | /r display raw list of memory blocks | /s display standard DOS memory | /v display device driver information | /x display extended (XMS) memory summary | | Additional options for /s display (these all imply /s): | /d display detail list of allocation by programs | /f display names of open files (DOS 3.0 or later) | /n display programs' environments | | Othe options: | /q quick display | ? display syntax summary Multiple switches may be specified together or separately. All of these are valid and equivalent: pmap /f /d pmap /fd pmap /f/d If you wish to set "permanent" options, i.e., options that will be in effect for every PMAP run, set an environment variable called PMAP to contain the desired option switches. For example, if you usually want to list only standard memory, with file handles, set PMAP as follows: SET PMAP=/s /f To override options set in the PMAP variable, you can follow any switch with an asterisk. For example, if you have the PMAP variable set as above but do NOT want to see the file handles for one run, use: pmap /f* | Selecting the primary display(s) | -------------------------------- | PMAP provides six primary displays: | | - standard (conventional) DOS memory (/s option) | - expanded (EMS) memory (/e) | - extended (XMS) memory (/x) | - the system kernel (/k) | - device drivers (/v) | - raw statndard memory blocks (/r) | | By default, PMAP displays the first three; as mentioned above, | you can change the default with the PMAP environment variable. | | The first occurrence of any of the above options, either on the | command line or in the PMAP variable, turns off all of the | others. Thus, if you type | | pmap /sk | | You will see only the standard memory and kernel displays--the | EMS and XMS displays are turned off. Similarly, if you use | | SET PMAP=/e | | you will, by default, see only the expanded (EMS) memory | display. | | Primary options set on the command line turn off any primary | options set in the PMAP variable: | | SET PMAP=/s | ... | pmap /x | | In the example, only extended memory is displayed. | | Note that the /d, /f, and /n options all imply /s, since they | affect only the standard memory display. Thus, | | pmap /d | | is equivalent to | | pmap /sd | | and will display only standard memory (including the details | requested by /d). Standard memory display ----------------------- The display of standard (conventional) DOS memory looks similar to this: Addr Program Parent Parameters Han Blks Size Vectors ---- ------- -------- --------------- --- ---- ------- ------- 147D command command main 0 2 3888 2E 157B nmi command /i/q 0 2 1856 02 15F2 cache-em command 500 0 2 13168 13 19 193E dbase command /C d:command 16 2 238384 30 ... Other allocated blocks 4 81296 Total conventional free memory 4 451696 Largest conventional free block 371168 Next program will load at 5579 Each program that is currently in memory is displayed. Fields are as follows: Addr The memory segment at which the program is loaded, in hexadecimal. If an asterisk (*) follows the address, the program is loaded into a disconnected high memory chain (see below). Program The name of the program, if available. "n/a" indicates that the name is not available. The program name is never available under DOS 2.x. Parent The name of the program's "parent". In most cases, this will be "command", because most programs are run by COMMAND.COM (i.e., from the DOS prompt). See below. Parameters The command line parameters that were specified when the program was run. Some programs re-use the area where the parameters are stored, in which case a "??" will be displayed. An ellipsis ("...") at the end indicates that there were more parameters than could fit here. Han The number of open handles (or files) associated with the owner. See below. Blocks The number of memory blocks that are owned by the program. Size The total size of all blocks owned by the program. Vectors A list of 80x8x interrupt vectors that appear to have been "intercepted" by the program. In the example, the program NMI is loaded at memory segment 157BH and was run directly from the DOS prompt or from a batch file. The original parameters were "/i/q". DOS has allocated two blocks of memory for the program, and they total 1856 bytes in size. Vector 2 (nonmaskable interrupt) has been "intercepted" by NMI. "Other allocated blocks" refer to blocks of memory that are not free but also are not owned by any executable program that PMAP can identify. They may be owned by device drivers or by DOS itself; or they may in fact be owned by executable programs but not indicated as such. PMAP may be able to make an educated guess as to the true owner; if so, the probable name of the program will be indicated in parentheses when you use the /D option switch (see below). At the end of the list, PMAP indicates the number of blocks of free memory, the total size of all free blocks, the largest single free block, and the segment address at which the next program will probably load. You can restrict the display to certain programs by naming them on the command line. For example, the command pmap sdump ced would display information for the SDUMP and CED programs, and no others. You can use a single wildcard '*' at the end of any named program in the list. For example, pmap sd* c* would display information for all programs beginning with "sd" or "c". NOTE: "below" the first program loaded in memory (usually COMMAND.COM), there is a block of memory allocated by DOS for device drivers, etc. PMAP does not show this block in the main display; its size is indicated under "Other allocated blocks" area if you request a detailed listing (/D), and further detail is available with the /K switch (see below). Detail display (/D) ------------------- When you run PMAP with the /D (Detail) option, you'll see the same display, except that PMAP will show a detailed list of memory blocks allocated for each program. For example: Addr Program Parent Parameters Han Blks Size Vectors ---- ------- -------- ------------- --- ---- ------- ------- 1666 kbfix2 command /KT1 /D0... 0 2 2560 08 09 16 1661 Environment 64 1666 Program 2496 KBFIX2 has two memory blocks allocated to it; PMAP shows the size of each block and its address, and makes an educated guess as to what the block is used for. You may include a list of specific programs to be displayed: pmap sdump ced /d PMAP also displays a detail list of all free blocks of memory and of "other allocated blocks". Environment display ------------------- If you add a /N switch, PMAP will display the contents of each program's environment (if there is one). For example, the command: pmap rxrun /n might display something like this: Addr Program Parent Parameters Han Blks Size Vectors ---- ------- -------- ------------- --- ---- ------- ------- B6D4 rxrun command 0 2 1536 Environment [B7E3] COMSPEC=C:\COMMAND.COM PATH=C:\UTIL;C:\DOS PROMPT=$p$g [name] C:\BOOT\RXRUN.COM The [B7E3] represents the segment address at which the environment is located. The [name] field appears only under DOS 3.0 and later; it shows the contents of the area of the environment where the full path and name of the program are stored. In some cases (especially in the case of COMMAND.COM), garbage may in fact be stored in this area. If PMAP think that the field is invalid, it will report "[name field invalid]"; however, PMAP may display invalid data if the contents of the field look like displayable characters. Open files display (/F) ----------------------- If the HAN field in the standard display is non-zero, the named program currently has files that are open. You can display the names of these files by adding the /F option. For example: Addr Program Parent Parameters Han Blks Size Vectors ---- ------- -------- ------------- --- ---- ------- ------- 12CD command command /f 1 2 4176 22 23 24 2E Open files: D:FOPT.TXT This feature is available only under DOS 3.0 and later and is mutually exclusive with the /Q (Quick) switch. Quick display (/Q) ------------------ Some of what PMAP does can be somewhat time consuming on slower computer systems, and one task may fail under some versions of DOS. If you would like PMAP to run slightly faster (about 1/2 second on a 4.77Mhz machine if you have EMS) or if PMAP fails with an error message similar to: pmap: error tracing buffer chain then use the /Q (Quick) option switch. With /Q set, PMAP will not: 1. Search for a disconnected high memory chain, or 2. Look for buffers, files, stacks, etc. The /K and /F options cannot be used with /Q. Also note that /Q will have little effect on PMAP's speed unless you have expanded memory (EMS), and that /Q is automatically set for DOS versions prior to 3.0. Remember, if you always want to use the /Q switch, you can SET PMAP=/Q in your environment. Kernel display (/K) ------------------- Below the first program loaded into memory (usually COMMAND.COM) there is an area of memory used by DOS for storage of code and data. This area is broken into three major sections: 1. IBMBIO's code and data. This is always located at memory segment 0070h and contains the basic code and data for system input/output services. The default device drivers (for the printer, screen, and keyboard, etc.) are also located here. 2. IBMDOS's basic code and data. This is located in memory immediately following IBMBIO's area and contains the "guts" of DOS. This area usually includes space for five FILES and one BUFFER. (Under DOS 5.0 with DOS=HIGH, part of this area is moved to the HMA.) 3. A supplementary DOS data area. This area may include: - your FCBs; the size is affected by the FCBS option in your CONFIG.SYS. - any FILES beyond the initial number (usually 5) that are stored in the IBMDOS area. This size of this area is determined by the FILES option in CONFIG.SYS. - any BUFFERS beyond the initial number (usually 1) that are stored in the IBMDOS area. The size of this area is determined by the BUFFERS option in CONFIG.SYS. - your logical drive table. There is one entry in this table for each drive up to LASTDRIVE. - your DOS STACKS, if any (DOS 3.1 or later only). The size of this area is determined by the STACKS option in CONFIG.SYS. - any externally loaded device drivers such as ANSI.SYS. To display a detailed map of the complete DOS memory area (all three of the above), use the /K option. The display might look something like this: MCB Addr End Size Contents ---- ---- ---- ----- -------- -- 0070 0279 8352 IBMBIO [includes 13 device drivers] -- 027A 09C7 29920 IBMDOS [includes 5 files, 1 buffer] 09C8 09C9 1282 35760 DOS data/drivers DOS data/drivers area detail: 09C9 0E9B 19760 8 device drivers (PMAP /V for detail) 0E9C 0F10 1872 35 files 0F11 0F1E 224 4 FCBs 0F1F 1191 10032 19 buffers 1192 11B5 576 7 logical drives 11B6 1282 3280 9 stacks (128 bytes each) The first section shows the locations and sizes of the three major areas used by DOS. In this case, for example, area 2 (the basic IBMDOS code/data area) begins at memory segment 027Ah and is 29,920 bytes in size. It includes five files and one buffer. The MCB field, which only appears for area 3, shows the address of the memory control block for the area. This is part of DOS's memory management scheme and is decribed in greater detail later in this manual. Areas 1 and 2 are not part of DOS's official memory chain, so they have no MCBs. The second section breaks down the contents of area 3 in greater detail. In the example system, eight device drivers are loaded and the system is configured as follows: FILES=40 BUFFERS=20 LASTDRIVE=G STACKS=9,128 FCBS=4,0 The display shows the exact location and size of each of these items. For example, the extra 19 buffers (there's one in area 2, leaving 19 of the 20 for area 3) are located at memory segment 0F1Fh and extend through the end of memory segment 1191h, a total of 10,032 bytes. If you use an extender program such as QEMM's FILES.COM to increase the number of FILES after bootup, storage for the extra files will be located elsewhere in the memory chain--not in any of the DOS data areas described. PMAP will display such areas in a separate section if there are any. For example, if we ran: FILES + 2 to increase the maximum number of files from 40 to 42, the display might appear as follows: Additional memory block(s) used for DOS data: MCB Addr End Size Contents ---- ---- ---- ----- -------- 1897 1898 18C8 784 >> 18C1 18C7 112 2 files This shows that the 944-byte block from 1403h to 143Dh (with MCB at 1402h) is used for supplementary DOS data. Within this 944-byte allocation, the 272 bytes from memory segments 142Ch through 143Ch contain the actual storage for information about the five files. Note also that, if there are additional blocks such as these, they are identified in the standard program display if you use the /D (detail) option. The above might look something like this in the detail display: Addr Program Parent Parameters Han Blks Size Vectors ---- ------- -------- ------------- --- ---- ------- ------- 1898 n/a command +2 0 1 784 1898 2 files 784 The /K option is available only under DOS 3.0 and later. Raw display (/R) ---------------- When you run PMAP with the /R (Raw) parameter, you'll see a display like this: T MCB Addr Owner Para Bytes - ---- ---- ----- ---- -------- M 0974 0975 0008 0AFA 44960 M 146F 1470 1470 00C3 3120 M 1533 1534 1470 0020 512 GLVMGR [more of the same] M 1DF3 1DF4 1DF4 0706 28768 M 24FA 24FB 2500 0004 64 [pmap] M 24FF 2500 2500 1376 79712 [pmap] Z 3876 3877 0000 6789 424080 This is an uninterpreted list of all blocks of memory allocated by DOS (see below). The fields are as follows: Type The block type. There are only two block types, type M and type Z. The last block in the chain is type Z, and all others are type M. MCB The segment address of the Memory Control Block (sometimes known as an arena header). Addr The segment address of the memory block itself. This is always equal to the MCB address plus one. Owner The segment address of the program that "owns" the block of memory. If this is 0000, the block is unallocated or "free". Para The size of the block, in paragraphs (16 bytes). Bytes The size of the block, in bytes. All numbers are hexadecimal except "bytes", which is decimal. The [pmap] suffix after an allocated block indicates that the block is being used by PMAP. When PMAP terminates, this block will be free (unallocated). The standard (non-raw) PMAP display understands this, and displays the map as if PMAP weren't there. Following some lines on the display you may see a one- to eight-character string: T MCB Addr Owner Para Bytes - ---- ---- ----- ---- -------- M 1533 1534 1470 0020 512 GLVMGR Under DOS 4.0 and later, a program name may appear in the last eight bytes of a memory control block (which is what the raw display is showing). Under DOS versions prior to 4.0, DOS does not place the program name in this location, but some other programs (such as 386MAX and QEMM) may do so. If PMAP thinks that the contents of the last eight bytes of the MCB look like a readable string, it will display the string. This may provide some information about the owner of the block. In some cases, the information in this area may be garbage that happens to consist of all ASCII characters--and these will be displayed. You should be able to tell at a glance which strings are meaningful and which are not. If PMAP is able to identify a disconnected high memory chain, it will display the line: Disconnected high memory chain: between the regular low-RAM DOS memory chain and the "hidden" high memory chain. If the /R switch is included, all other command line parameters are ignored. Expanded memory display (/E) ---------------------------- If expanded (LIM or EEMS) memory is present and you have not specified /E*, PMAP displays EMS allocation as follows: Expanded memory summary: Block Size Name ----- ------- ---- 0 589824 SYSTEM 1 425984 2 16384 CDIR 3 65536 HINDSITE ... Free 327680 Total 2097152 Page frame segment: CC00h The NAME field will be present only if your expanded memory manager supports the LIM 4.0 specification, and then only for programs that have defined their names to the system. EMS memory uses a "page frame" that maps a 64K block (actually, four 16K "pages") of EMS memory into standard 80x8x memory. The segment to which this memory is mapped is also displayed. | Extended memory display (/X) | ---------------------------- | If extended memory (XM) is present and you have not specified | the /X* option, PMAP displays XM information as follows: | | Extended memory summary: | | INT 15 ext mem available 0 | XMS version 3.00 (vendor 5.12) | HMA enabled, in use | Free XMS 458752 | Largest free block 458752 | | XMS handles in use: | Handle Size Address LkCt | 1 32768 00110000 1 | 2 277504 00118000 -- | | "INT 15 ext mem" refers to AT-style extended memory that is not | managed by an XMS driver. This type of memory is used primarily | by older devices such as VDISK. | | The remaining information is shown only if an XMS (eXtended | Memory Specification) driver is present in the system. XMS | drivers manage extended memory by allocating and providing | access to blocks of XM as requested by system and application | programs. Among such drivers are DOS's HIMEM.SYS, Qualitas's | 386MAX, and Quarterdeck's QEMM. | | "XMS version" is the version number of XM Specification that is | supported by your XMS driver. Following this is the vendor's | internal version number for the driver software. | | "HMA" refers to the High Memory Area, a block of memory | approximately 64K in size at the very top of your CPU's real | mode address space. The HMA is special because it includes the | only addresses above 1MB that can be accessed by the CPU in real | mode (which is the mode DOS normally uses). Current XMS | managers allocate this space to one, and only one, program at a | time. HMA is the are of memory that is used by DOS 5.0 when | DOS=HIGH is specified (thus moving most of DOS out of the lower | 640K). PMAP's report shows whether or not the HMA is enabled | and, if so, whether or not it is in use. | | "Free XMS" shows the total amount of XMS-managed extended memory | that is current available for allocation, in bytes. "Largest | free block" shows the size of the largest single free block of | XMS-managed memory. | | If any XMS-managed memory is currently allocated, the "XMS | handles in use" section displays additional information. For | each active XMS "handle" (each block of extended memory | allocated by the XMS manager is assigned a handle), PMAP | displays the handle number, the size of the block in bytes, and | the 32-bit linear address of the block (in hex). If the block | is currently "locked" (guaranteed not to move), PMAP displays | its non-zero "lock count", which is the number of times it must | be unlocked before it is once again movable. Most blocks should | be unlocked most of the time. Device driver display (/V) -------------------------- If you execute PMAP with the /V switch, it will display a table of information about your installed device drivers. No other data (i.e., no memory maps) are displayed when /V is selected. The first five columns of the table contain the following fields: Name If the device is a character device, the device name. If it is a block device (like a disk), this will be "Blk (n)", where n is the number of units handled by this device. Address The address where the device driver begins in memory, in standard hex segment:offset form. Size The approximate size (in bytes, displayed in decimal) of the device driver. See below. Strt The entry point of the driver's strategy routine. This is the hex offset within the device driver's segment (shown under ADDRESS). Intr The entry point of the driver's interrupt routine. This is the hex offset within the device driver's segment (shown under ADDRESS). The remaining columns are bit fields with the driver's attribute record. In each case, an asterisk indicates that the bit is set (1), and a space indicates that it is reset (0). CHR * = this is a character device <sp> = this is a block device. IOC * = device supports IOCTL calls IBM for block devices: * = non-IBM format for character devices: * = supports output-until-busy RMV * = supports removable media LOG * = supports Get/Set Logical Device CLK * = this is the clock device NUL * = this is the NUL device SOT * = this is this standard output device SIN for block devices: * = supports generic IOCTL for character devices * = this is the standard input device Note that <space> implies the opposite of <*>; for example, an asterisk in IOC indicates that the device supports IOCTL calls, while a space there indicates that IOCTL is not supported. Also note that DOS does not provide any documented way for programs to find the chain of device drivers. If PMAP is unable to find the chain, it will tell you so. Device driver size; order of list --------------------------------- PMAP cannot reliably determine the size of the default devices (CON, PRN, AUX, COM1, etc.) that are loaded automatically by DOS (they share code and data). These will all show an address beginning with "0070", and their sizes will not be displayed. However, if you load a replacement for one of these devices (for example, ANSI.SYS loads a replacement for CON), PMAP will generally be able to determine and display its size. The devices are shown in the order in which DOS searches for them. If there are two or more devices with the same name, the one that DOS will use is the first one listed. For example, you will have two or more CON devices if you use ANSI.SYS; the ANSI.SYS CON will be listed before the default CON. DOS will use the first one listed (ANSI.SYS). Disconnected high memory chains ------------------------------- DOS manages memory by using a "chain" of allocated memory blocks as described below. This chain normally ends at the 640K mark (segment A000), as memory addresses above this address are reserved for use by video adapters (some programs such as EEMRAM, QEMM, and 386MAX may extend the chain to B000 or B800). By following the links in this chain, PMAP is able to map your DOS memory and determine what programs own what areas of memory. However, Quarterdeck's QEMM and Qualitas' 386MAX may create an additional chain of allocated memory blocks in "high RAM" above the video adapter memory area. Using a "high load" feature, these programs can load your resident utilities and device drivers into the high RAM chain, thus increasing the memory available to DOS in low RAM. The high RAM chain is not connected to DOS's standard low RAM chain (unless you use 386MAX's OPENHIGH option), and versions of PMAP prior to 2.0 would not find it; therefore programs loaded into high RAM were not displayed. Beginning with version 2.0, however, PMAP attempts to locate these "high memory chains" and identify the programs loaded there. If PMAP succeeds in finding the chain and there are programs loaded in it, such programs will be marked with an asterisk (*) in the program display. In raw block display mode (/R), the two chains (low and high) are shown separately. NOTE: PMAP has no internal knowledge of QEMM, 386MAX, or similar programs; the presence of high memory chains is determined empirically. The possibility exists that PMAP may occasionally report an artifact chain: something that looks to PMAP like a high memory chain but really isn't. You should be able to tell by looking at the displays (especially the /R raw display) if such a chain has been found. Interrupt vectors ----------------- Many times interrupts are "intercepted" by more than one resident program. PMAP will only show a vector attached to the LAST program that intercepted it. For example, in the sample display shown for the /D (Detail option), KBFIX2 shows that it has intercepted vectors 8, 9, and 16. However, RXINTMGR and SDUMP could also have intercepted any or all of these three vectors, and PMAP would not know about that. PMAP assumes that any vector that points into memory owned by a program has been intercepted by that program. That is not always true, so you may occasionally see spurious vectors attached to a program. More about parents ------------------ Every program has a "parent"; if program B was executed by program A, then A is B's parent. In most cases, the parent will be COMMAND.COM, because most PC programs are executed by COMMAND.COM. However, any program can execute any other program (assuming that there is sufficient memory, etc.). This is how "shells" work. For example, current versions of WordPerfect and many other programs allow you to "exit to DOS"; what they usually do is execute COMMAND.COM, which then displays a DOS prompt and allows you to enter any commands that you wish. If you run PMAP, you will see two copies of COMMAND.COM in memory. However, you may notice that the second copy of COMMAND.COM shows COMMAND.COM as its parent. Logically, you would expect the parent to be (in this case) WordPerfect. Unfortunately, some versions of COMMAND.COM (the one that comes with DOS 3.2, for example) fool around with the area of memory that PMAP uses to find the parent's address; rather than having the parent's address, COMMAND.COM puts its own address there. In effect, COMMAND.COM is always its own parent. In general, programs that allow you to execute other programs can use one of two methods: they can execute the other programs directly, or they can execute COMMAND.COM and ask it to run the requested program. If the former case, PMAP will show the true parent; if the latter, PMAP may show COMMAND.COM as the parent, and COMMAND.COM will be its own parent. Here is part of a PMAP display that shows a direct-execution under DOS 3.2: Addr Program Parent Han Blks Size Vectors ---- ------- -------- --- ---- ------- ------- ... 3222 xced command 0 2 26016 387E qe xced 0 3 97232 503E command command 0 3 3488 22 23 24 ... The XCED program was run by COMMAND.COM (from the DOS prompt). It then ran the program QE directly, i.e., without reloading COMMAND.COM; QE's parent is correctly shown as XCED. Finally, a "shell" exit was taken from QE, which did reload COMMAND.COM; notice that COMMAND shows as its own parent. The second COMMAND.COM's real parent is QE, but this is not shown correctly. File handles ------------ The "Han" field of the standard memory display shows the number of file handles that are associated with each program. For the most part, this field will be zero. Some open handles may show for programs that are active (for example, the active program named "dbase" in the first example has 16 open files). Use the /F option to see the names of the open files. You may see some resident programs that show one or more open handles. This usually occurs when you redirect the program's start-up logo to NUL, and the program fails to close its standard files before exiting back to DOS (this really shouldn't be necessary, but it is). These open handles may reduce the number of files your application programs can have simultaneously open. We prefer not to redirect programs' logos to NUL. We save file handles; we get to see the names of the nice people who wrote our software, and their copyrights; and we don't lose the error messages that explain why the program isn't doing what we thought it should. Sounds like a bargain. Multi-tasking/task-switching programs ------------------------------------- ... play havoc with the memory allocation chain. PMAP may not yield very much useful information under such programs. DOS's memory allocation chain ----------------------------- This information is almost totally undocumented by Microsoft, so take it for what's it's worth. It's provided for informational purposes only, and could vary from DOS version to DOS version. However, the basic structure of the memory allocation scheme has remained unchanged from DOS 2.0 through the version that is current as of this date (5.0). Only the program name field has changed--it was added with version 4.0. DOS (version 2.0 or later) manages memory as a chain of "blocks" or "arenas". Each block begins on a paragraph boundary, can be (in theory) almost a megabyte in size, and is preceded immediately by a 16-byte Memory Control Block (MCB), sometimes known as an "arena header". The lowest (the 80x8x interrupt vectors, BIOS and DOS data areas, DOS itself, device drivers, etc.) and highest (video buffers, ROM modules) portions of memory are not mapped, but the rest of memory is. Thus, memory can be pictured like this: paragraph contents --------- 0000 low memory (unmapped) first MCB (16 bytes) first memory block next MCB next memory block ... last MCB last memory allocation block nnnn end of DOS memory (640K, for example) The address of the first MCB will vary, depending on your version of DOS and the number and size of device drivers, buffers, stacks, etc., that you loaded via CONFIG.SYS. In all current versions of DOS (verified through 5.00), the segment address of the first MCB can be obtained via DOS function 52H. On return from this function, the address of the first MCB is located at ES:[BX-2]. Here is sample code that returns the address of the first MCB in AX: mov ah,52H int 21H mov ax,es:[bx-2] The MCB itself is a 16-byte region of memory that with fields as follows: Offset Size Contents ------ ---- -------- 0 Byte 'M': this is not the last MCB 'Z': this is the last MCB anything else: memory control blocks destroyed. DOS will politely crash. 1 Word The segment address of the program that owns this block of memory (the program's PSP). 3 Word The size of the block, in paragraphs 5-7 Reserved 8-15 n/a 8-char (blank-filled) name of owner program (DOS 4.0+ only) This structure provides all of the information needed to step through the memory allocation chain. A basic algorithm is as follows: Set MCB = segment of first MCB (as described above) Do Until byte (MCB:0) = 'Z' If byte (MCB:0) isn't 'M' or 'Z', Then there's a big problem (the system is about to crash with a "memory allocation error") Block_owner = word (MCB:1) Block_size = word (MCB:3) MCB = MCB + block_size + 1 End EMS and XMS memory is not mapped by DOS. For more complete detail about DOS's memory allocation, see "Managing Memory" by William J. Redmond in PC Tech Journal, August, 1984 (Vol. 2, No. 2). Version 2.10 (7/3/91) --------------------- - Adds support for XMS drivers. - Reworks option switches. - Supports DOS 2.x and 3.x programs that deallocate their environment and place a smaller environment (containing just the program name) in their own primary allocation block. - Displays all selected primaries; previous versions would display (e.g.) only the kernel if /k was selected. - Fixes a problem that caused some deivces to show negative sizes. Version 2.03 ------------ Fixes a problem in displaying disconnected high-memory chains and resident programs loaded there. Version 2.02 ------------ - Fixes a problem with the "largest conventional free block". - Fixes problems with sizes of certain device drivers. - Fixes problem with stack size display when "STACKS=0,0". - Doesn't show the DOS data area as "unallocated". - Increases the maximum allowable number of files, buffers, and FCBs to 255 each (from 100). - Reduces chance of displaying spurious high memory chains. - Displays name field of environment (/E switch) only if all characters in the field are in the displayable ASCII range (33..127). - Displays name field in raw display only if the field contains an 8-character, blank-filled, displayable ASCII string, and only if the block owns itself (implying that it's a program). - Shows segment address of environment (/E switch). Version 2.01 (6/7/90) --------------------- Fixes a problem that prevented PMAP from working on systems with no expanded memory. Version 2.00 (6/5/90) ----------------------- - Attempts to identify disconnected high-RAM chains - Adds /F (files) option - Adds /E (environment) option - Adds /K (kernel display) option and identifies areas of the DOS data block used for files, buffers, stacks, etc. - Adds /Q (quick display) option - Supports permanent options via PMAP variable - Correctly reports size of last installed device driver - Supports altered switch characters - Shows program name in raw display if available from environment. - Uses correct number of available file handles with extended handle tables (old versions assumed 20 handles) Version 1.34 (11/15/88) ----------------------- Fixes a bug in 1.33 for resident programs that release their environments under DOS 4.0. Version 1.33 (11/14/88) ----------------------- Uses a new feature of DOS 4.0 to more reliably obtain names of resident programs, including those installed via INSTALL. Version 1.31/1.32 (7/29/88) --------------------------- Displays number of open handles for each PSP. Displays sizes of some devices (/V switch). Improved display when too many vectors to fit on one line. Fixed spurious errorlevel returned by successful run (32). Version 1.30 ------------ Adds /X, /S, and /? switches. Adds device driver display (/V). Displays names of EMS-users when available (LIM 4.0 only). Allows wildcards in program-list. Fixes problem with name of secondary copies of COMMAND.COM under DOS 3.3 (it's not available). Version 1.26 ------------ Corrects a problem detecting extended memory with certain versions of BIOS ROM. Version 1.25 ------------ Adds the extended memory display and the selective display option. Corrects a minor problem with DOS 3.3. Version 1.21 ------------ Bug fixes to version 1.20: 1. No more runaway display when EMS memory is present but none of it is in use. 2. PMAP is more careful about what it thinks is the name of the command shell. Copyright/License/Warranty -------------------------- This document and the program file PMAP.EXE ("the software") are copyrighted by the author. The copyright owner hereby licenses you to: use the software; make as many copies of the program and documentation as you wish; give such copies to anyone; and distribute the software and documentation via electronic means. There is no charge for any of the above. However, you are specifically prohibited from charging, or requesting donations, for any such copies, however made; and from distributing the software and/or documentation with commercial products without prior permission. An exception is granted to not-for-profit user's groups, which are authorized to charge a small fee (not to exceed $7) for materials, handling, postage, and general overhead. NO FOR-PROFIT ORGANIZATION IS AUTHORIZED TO CHARGE ANY AMOUNT FOR DISTRIBUTION OF COPIES OF THE SOFTWARE OR DOCUMENTATION, OR TO INCLUDE COPIES OF THE SOFTWARE OR DOCUMENTATION WITH SALES OF THEIR OWN PRODUCTS. THIS INCLUDES A SPECIFIC PROHIBITION AGAINST FOR-PROFIT ORGANIZATIONS DISTRIBUTING THE SOFTWARE, EITHER ALONE OR WITH OTHER SOFTWARE, AND CHARGING A "HANDLING" OR "MATERIALS" FEE OR ANY OTHER SUCH FEE FOR THE DISTRIBUTION. NO FOR-PROFIT ORGANIZATION IS AUTHORIZED TO INCLUDE THE SOFTWARE ON ANY MEDIA FOR WHICH MONEY IS CHARGED. PERIOD. There is no restriction on the use of this software in commercial or institutional environments. No copy of the software may be distributed or given away without this document; and this notice must not be removed. There is no warranty of any kind, and the copyright owner is not liable for damages of any kind. By using this free software, you agree to this. The software and documentation are: Copyright (C) 1986, 1987, 1988, 1990 by Christopher J. Dunford The Cove Software Group P.O. Box 1072 Columbia, Maryland 21044 (301) 992-9371 CompuServe 76703,2002 [IBMNET]