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Chapter 4 - Memory Management The amount of memory used by ConIX, internal machine code organization, how ConIX manages memory usage, freeing memory for program usage, overall system memory layout, and the way ConIX treats memory from the user's standpoint. - CONTENTS - __________________________________________________________________ 4. Memory Management...................................... 4-1 4.1 Management Levels................................... 4-2 4.2 ConIX System Memory Map............................. 4-4 4.3 Memory Usage Rules.................................. 4-6 4.4 Notes............................................... 4-7 - i - ConIX Operating System Memory Management 4. Memory Management ConIX is very small considering the number of features it provides. However, its approximate 25K size is enough to take a sizable chunk out of the memory available in any micro. The crunch can be most harshly felt in the reduced workspace for programs, such as text editors, which need as much memory as they can get. Some programs make you pay in memory for their features. Not ConIX! The test of time proves any program's usability. If a program is cumbersome to use, it will simply fall into oblivion on some dusty shelf. To prevent such a dreary destiny for our program, we have devoted much time to making ConIX be more of a benefit to the user, rather than a detriment. The environment it provides is extremely powerful and useful, while it has many features and settings designed to make sure it will not get in the way of what you want to accomplish. Memory Management is one of those features. Simply defined, Memory Management is the process by which ConIX manages the amount of TPA memory it occupies in your system. The time when you usually need as much memory as possible is when running a program, so that more data can be kept in active workspace. It is at this point that you can select the amount of memory allocated for use by ConIX. There are eight different levels of Memory Management which can be set by the user, depending upon how much memory is needed. Each level corresponds to a segment of the ConIX machine code which is actively stored in memory. Set at its highest level (8), ConIX will take up as little as (12K of TPA memory! Such a small amount of memory will definitely go unnoticed when you're running any of your CP/M programs. The first is the lowest level of Memory Management. When set at this segment, no management takes place and ConIX occupies the maximum amount of memory which it needs to reside, in its entirety, in your system. Every time you move up one level, all previous levels get thrown out of memory before the execution of a disk-based command. The space occupied by the discarded levels is then made available for use by the running program. Once the program finishes execution, ConIX automatically reloads only as much of itself as is needed to process your commands (to level 5). If you request a built-in command from a segment of ConIX which is not currently in memory, then only that segment will be loaded. All reloading is done from the original CONIX.COM file, which was used by CP/M to bring ConIX into your system initially. The memory manager will look for this file in the default directory which was set when the initial CP/M load took place. This location may be changed with the OPT +CX internal command. 4-1 Memory Management ConIX Operating System The Memory Management level can be set by using the OPT +/-MM internal command, as: <A:00> opt +mm <#level> The specified level number will be the default each time a disk- based program is executed. For example, typing: <A:00> opt +mm 5 will set ConIX to invoke Memory Management and remove code from level 1 to 4 each time a command is loaded from disk. Execution of an internal command can only increase the amount of memory being used by ConIX since the command may lie in a segment which had been managed out of memory. However, this increase is only temporary as these segments will again be freed when another .COM program is executed. The Memory Management level may also be modified for a single program by typing: <A:00> [m=<#level>] command (arg(s)) This change is only temporary as the default level set by OPT +MM will once again be used for all following commands, unless respecified. Memory Management is a fast and efficient means by which you can allocate space for program execution. With this feature, you can be sure that ConIX will never get in your way! 4.1 Management Levels The eight levels of Memory Management serve to group the ConIX internal machine-code segments by different functions. These segments, and the functions contained within them, are described below. Level 1: Programming Functions This is the topmost level of ConIX (where the top is the beginning and the bottom is the end of the ConIX machine code). It contains data manipulation commands which are most often used only within a Command Language program. Level 2: XCC Commands This is the segment which contains the instructions necessary for the execution of Command Language programs. It is, therefore, only used when such a program is running. 4-2 ConIX Operating System Memory Management Level 3: General Utilities The commands within this segment are used more often than those in the first segment, but not as often as those in the fourth. It is an in-between group, mainly intended to break up the size of the entire Utilities code section. Most of the commands stored here are used for manipulating memory. Level 4: Utilities These are the most often used commands or utilities. You are most likely to access this segment more often during the course of using your system than any other level above it. For example, the DIR and ERA commands reside here. Level 5: Command Line Setup This segment is significantly larger than any of the previous ones. It contains the Command Line Processor, or parser, which performs all the command line setup such as decoding arguments and variables. It also contains the loader, which searches internally and on disk for the commands you enter. After the command is found, the selected redirection buffers and routines are activated within this segment. Needless to say, this section must be around in order to process your commands. Therefore, if Memory Management is set to a higher level (above 5), this section and everything which is ``managed out'' below it, must always be reloaded after the execution of a disk-based program. To prevent delays after running programs, we recommend that Memory Management be set by default (using the OPT +MM internal command) to this level, namely 5. If you must occasionally execute a program that requires more memory, specify a higher level of management using the [M] Command Line Option. If you run programs that need a lot of memory more often than not, then specify the default level to be higher than 5. When you run a command that does not need that much memory, specify a lower level of management using [M], to prevent memory from being freed unnecessarily. Level 6: Redirection and SysCall Decoder This is the most important segment of ConIX because it contains all of the run-time features which programs might utilize during their execution. For example, Redirection, Print Spooling, and Function Keys are included within this section. When Memory Management is set to level 6 or lower, you will lose absolutely nothing as far as features are concerned. ConIX will handle itself properly knowing the memory usage restrictions imposed upon it by the user and no functionality will be lost 4-3 Memory Management ConIX Operating System because of this. However, if this section is managed out (management level set above 6), a program will run exactly as it would under regular CP/M, which means that all the ConIX features would be lost during execution. The features will, of course, return for use by the built-in commands, but they will be inaccessible to disk-based software. Therefore, whenever possible, this level should not be managed out, so as to prevent such a drastic loss from occurring. Level 7: Permanent Data Storage This is the section where the ConIX ``internal'' data values are stored. All the changes and customizations of features which were made during the course of using ConIX are recorded in this section. If it is managed out (i.e., management level set to 8), the data stored in this section (about 4K) must be saved so that the user's changes will remain when ConIX returns. This is done by writing the permanent data area to a disk file, CONIX.DAT, stored in the default directory which was externally set when ConIX was first loaded from CP/M. If CONIX.DAT already exists and is set to R/O, it will not be overwritten and the file CONIX.DA$ will be used instead. In any case, the temporary file will be created with its SYS attribute set and deleted once ConIX is reloaded. The OPT +CD internal command may be used to change the directory which will hold this file. Level 8: System Loader This is the highest possible level of Memory Management. All of ConIX is gone except for a very small loader which reloads the permanent storage section (level 7) from the temporary file CONIX.DAT/$. Level 7 also contains the Memory Management code which is then used to reload ConIX to level 5 so that additional commands can be processed. 4.2 ConIX System Memory Map When running ConIX, your system's memory will be organized in the following way: 4-4 ConIX Operating System Memory Management ___________________________ | | | Page 0 | | Reserved for System Use | | | --------------------------- | | | Transient Program Area | | | --------------------------- | | | Transient Program Area | | and ConIX | | | --------------------------- | | | ConIX Loader | | | --------------------------- | | | CP/M BDOS | | | --------------------------- | | | BIOS | | | --------------------------- The first block of memory is page zero which starts at location 0000h and is reserved for certain system functions, such as: 0000h Warm Boot 0001h BIOS Address 0005h BDOS SysCalls 0006h End of TPA + 1 005Ch Default FCB (36 bytes) 0080h Default DMA (128 bytes) The next area in system memory is the TPA, which is active memory used to store and execute disk-based (.COM) programs. ConIX occupies part of the TPA memory, the amount of which depends upon the Memory Management level in effect. This is also the area where the CCP resided before ConIX took its place. Following ConIX is the loader segment which is a small (12K byte program that reloads ConIX when it is entirely managed out (level was set to 8). Finally, comes CP/M itself and the BIOS system-dependent functions. These segments might not always be resident in this area of memory if your system is running a CP/M emulator, or implements memory bank-switching. Consult your system manuals for more information about the particulars of your CP/M implementation. 4-5 Memory Management ConIX Operating System 4.3 Memory Usage Rules It is quite obvious that a disk can hold much more data than active computer memory, as most disks can store more than the 64K bytes of memory that an 8-bit processor can address. Therefore, it would seem logical to use the disk for operations which would not fit into memory. Most programs operate as such if they must handle data which can vary either small or large, as a program for a compiler, or a text file for an editor. If such a program is to be efficient, it will try to use as much memory as possible before going to disk for the remainder of the data. This is the fastest method, as memory is electronic and not mechanical like a disk, and should be used instead of disk whenever possible. ConIX internally does exactly that by managing how much memory is actually needed at one time. But there is actually more that the user can do with memory than ConIX can do for itself automatically. A great deal of the flexibility, speed and convenience offered by ConIX lies in its attitude towards the way memory is to be used. ConIX contains many functions which allow you to specify the areas of memory in which certain operations are to take place. You are given the freedom to use any part of memory that you like. It is entirely left up to the user to specify memory which will not interfere with the data storage and functions of ConIX itself. The user should be aware that all memory is volatile, and may be changed at any time by a running program, or by ConIX itself. The operation of ConIX is most definitely predictable, as you can always determine its start address with the TOP internal command. Any memory between location 100h and this address may be utilized for memory functions. This area is called the Transient Program Area, or just TPA. Many disk programs use only a set, or at least predictable amount of memory. You can usually figure out how much memory is available for holding some more permanent data. Generally, most ConIX internal commands do not break into the TPA, so if you don't run a program off disk, you can pretty much be assured that this memory will remain untouched. If an internal command will modify the TPA segment of memory, then it will be clearly mentioned in this manual. Memory is highly recommended for use with data which is small enough to be stored without any loss. If you specify a segment of memory which is not large enough to hold the given data, ConIX is smart enough not to exceed its bounds and simply excludes the remainder. Although levity in assigning memory can be quite fatal, if used carefully, you can achieve execution speeds which rival the larger minis. 4-6 ConIX Operating System Memory Management 4.4 Notes The amount of memory required by a program is usually dependent upon its size and the amount of space required for storing run- time data. If a program is too large to be loaded into available memory, ConIX will print an appropriate error message and abort. At this time, you should keep setting a higher Memory Management level until the program can load. Once the program is loaded, it may not execute or run properly due to a lack of memory. If this is the case, you should try an even higher level. But remember, once you pass level 6, programs can no longer take advantage of ConIX features. We have found programs like WordStar and dBase II to run fine at level 6. (The command line option string we use is [m=6,f,o].) 4-7 >-σHAPTER7DOC NÇσHAPTER7DOC ^-σHAPTER8DOC dÇ: