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Text File | 1987-04-11 | 17.1 KB | 394 lines

PMAP 1.21 --------- PMAP (Program MAP) is a simple program that displays how your PC's memory is being used. It lists all active programs (including resident programs such as Sidekick and PCED) and tells you how much free memory is available for programs. If expanded (LIM) memory is present, a summary of EMS use is also shown. Syntax summary -------------- pmap (display memory usage) pmap /d (display detailed memory usage) pmap /r (display raw memory allocation chain) Standard display ---------------- When PMAP is invoked without parameters, you'll see a display like this: Addr Program Parent Parameters Blks Size Vectors ---- ------- -------- ----------- ---- ------- ------- 1470 command command 2 3632 22 23 24 2E 155C rxintmgr command 2 1408 60 15B6 sdump command 2 2816 05 1666 kbfix2 command /KT1 /D0... 2 2560 08 09 16 1708 fastvr command 2 576 172E ced command ?? 2 26976 1B 61 1DC6 raw command ?? 2 688 1DF4 cache-em command /1312 /t 2 28848 13 19 21 Total conventional free memory 1 503888 Largest conventional free block 503888 Next program will load at 2500 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. Program The name of the program, if available. "??" 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. 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. For example, the program KBFIX2 is loaded at memory segment 1666H and was run directly from the DOS prompt. The original parameters were "/KT1 /D0" and there were more parameters than can be shown here. DOS has allocated two blocks of memory for the program, and they total 2560 bytes in size. Vectors 8 (timer tick), 9 (keyboard interrupt), and 16 (keyboard service) have been "intercepted" by KBFIX2. 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. 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 its standard display. If you are interested to see how large it is and where it is allocated, use the /R display described below, in which it will be the first block listed; it will usually show 0008 in the "owner" field. Detail display -------------- When you run PMAP with the /D (Detail) parameter, 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 Blks Size Vectors ---- ------- -------- ------------------ ------- ------- 1666 kbfix2 command /KT1 /D0... 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. PMAP also displays a detail list of all free blocks of memory. Raw display ----------- 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 [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. Expanded memory display ----------------------- If expanded (LIM-EMS, or EEMS) memory is present, PMAP always displays EMS allocation as follows: Expanded memory summary: Block Size ----- ------- 0 98304 1 1409024 Free 0 Total 1507328 Page frame segment: CC00h Like standard DOS memory, EMS memory is allocated in blocks. However, no information is easily available regarding the blocks except their sizes, so that is all that is displayed. 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. 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, 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 the can execute COMMAND.COM and ask it to run the requested program. If the former, PMAP will show the true parent; if the latter, PMAP will show COMMAND.COM, 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 Blks Size Vectors ---- ------- -------- ---- ------- ------- ... 3222 xced command 2 26016 387E qe xced 3 97232 503E command command 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. Finally, a "shell" exit was taken from QE, which did reload COMMAND.COM; notice that COMMAND shows as its own parent. 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. DOS (version 2.00 or later) manages memory as a chain of "blocks". 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 very lowest portions of memory (containing the 80x8x interrupt vectors, BIOS and DOS data areas, DOS itself, device drivers, etc.) are not mapped, but all of 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 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 (through 3.21), 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 5-15 Reserved 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 Block_owner = word (MCB:1) Block_size = word (MCB:3) MCB = MCB + block_size + 1 End EMS and EEMS memory is not, of course, 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 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 by Christopher J. Dunford 10057-2 Windstream Drive Columbia, Maryland 21044 (301) 992-9371