The Programmer's Guide to TRSDOS Version 6 - Tim Mann's Home ...

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Error 37: Illegal access attempted to protected file This indicates that an access request was made for a file that was password protected and the access protection level was not met for the request. Check if the disk is write protected. Error 38: File not open A file access operation was requested using a File Control Block that indicated a closed file. Most likely, there was a program error. Error 39: Device in use A request was made to REMOVE an active device from the Device Control Block table. It is necessary to first RESET a device before removing it. Error 40: Protected system device A request was made to REMOVE a standard system device. You cannot remove system devices such as *KI, *DO, *PR, *JL, *SI, and *SO. Error 41: File already open A request was made to open a file that was already open with an access level of UPDATE or greater. If you are in a single user environment and you know that the file is not open, you can reset the "open" indication by issuing a "RESET filespec" command. Error 42: LRL open fault This error indicates that a file was opened with a logical record length passed in the open linkage that differed from the file's LRL as stored in its directory. The file will be properly opened with the LRL passed in the open. This error is for information only. Error 43: SVC parameter error This error will be returned by a SuperVisor Call when one or more parameters associated with its register linkage contain invalid values. Error 44: Parameter error This error is returned by the parameter scanner when it detects in invalid command line parameter string. The error is usually caused by a misspelled parameter name or value, use of an unsupported abbreviation, or by entering a parameter that does not exist for the command invoked. Errors 45-62: Unknown error code Error codes in this range may not be defined by the operating system. Any time the @ERROR routine is called with an error number in this range, the "Unknown error code" message will be displayed. It most likely indicates a software problem. Error 63: Extended error This error code is used to indicate that an extended error code is in register pair HL. The @ERROR routine will display "** Extended error, HL = X'nnnn'" if called with error- 63. 8-13
8.5 HEADER PROTOCOL OF MEMORY MODULES A module of code can be relocated into high memory so that it's last byte is positioned at the value returned from the @HIGH$ SuperVisor Call. The module is then protected from being overwritten by other modules by adjusting HIGH$ to point to the address preceding the start of the module. Modules relocated and protected in this manner, must include a standard header that identifies the module. Modules placed into the low memory I/O driver region also must adhere to this standard. The header is used by the system to accomplish a number of important functions. First, it provides a locatable storage region for pointers used in the device independent library operations. Second, it provides a name string used by the @GTMOD SuperVisor Call to locate a specific module. Other data contained in the header provides the information needed to identify the entry address of each module so protected. The following code describes this standard header: ENTRY JR BEGIN ;Branch around linkage STUFHI DW $-$ ;To contain last byte used DB MODDCB-ENTRY-5 ;Calculate length of 'NAME' DB 'MODNAME' ;Name of this module MODDCB DW $-$ ;To contain DCB pointer for module DW 0 ;Reserved by the DOS ;*=*=* ; Area that can be used to store data ;*=*=* . BEGIN EQU $ ;*=*=* ; Actual module code start ;*=*=* Let's examine this module header line by line so that you gain an understanding of its purpose. At the label "ENTRY", the header always will have a relative jump instruction. The operand of the jump will almost always reference the starting address of your module. An exception to this would occur if the data area was extensive so that it placed the label "BEGIN" beyond the range of the jump relative instruction. If such was the case, you must provide an absolute jump (JP) instruction just prior to the data area. The address of this instruction will then be used as a reference in the operand field of the ENTRY jump relative. It is also possible that the "module" is not a program but rather a data area that you have reserved. This data area must still have a memory header; however, since there exists no BEGIN address, it is recommended that you reference the operand of the ENTRY jump relative instruction so that it jumps to ENTRY (i.e. jumps to itself). This is the second exception. The 2-byte storage region identified by the label STUFHI must be loaded with a value equal to the last memory address used by the module. The program routine that relocates the module into its memory position is responsible for loading this value. The system's @GTMOD routine uses the value to be able to branch sequentially from module to module. If the module is placed into high memory, this address value is the value returned by @HIGH$. The next two fields of the header are the name LENGTH and NAME fields. The NAME field will contain the module's name as assigned by the programmer. This is the name string that is used in the @GTMOD SuperVisor Call to locate the module. The name must range from characters in length and cannot have any character value below X'20'. The length of the name is then placed into bit positions 0-3 of the LENGTH field. The system uses the length value to determine how many characters must be matched in the NAME field. Bits 4-7 of the LENGTH byte are reserved by the operating system. 8-14
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MISOSYS, INC. The Programmer's Guid
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1. Introduction Many thousands of u
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language (i.e. BASIC, C, PASCAL, ..
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NAME START END DESCRIPTION LOWCORE
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ackup utility provides exceptional
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3. Device Input/Output Interfacing
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3.2.2 VECTOR Field - This field in
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FILTER *PR USING *S0 the operating
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===================================
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===================================
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ENTRY JR BEGIN ;Branch around linka
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DATA1 EQU $-DATA$ DB 0 ;Data storag
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Offset Contents +0 Contains the las
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image of the serial port UART statu
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called TRACKs. Each track is then d
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The DCT contains the information re
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accessed a single-sided diskette, t
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containing the disk's directory. Th
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Command Purpose RESTORE Recalibrate
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available from Logical Systems, Inc
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exceeds this capacity, then it must
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is two physical cylinders. Although
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5. The DOS Directory Structure 5.1
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===================================
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5.2.8 PACK NAME - This field conta
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The position of a file's hash code
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5.4 THE DIRECTORY RECORD STRUCTURE
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Bit 3 Specifies the visibility; if
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the first granule in use is the sec
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travels the turnpike. In this manne
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The @FSPEC SVC will transfer the fi
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A high level language permits you t
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does exist, @RENAME should return e
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Next, it would be very useful if th
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LD HL,FCBX+9 ;Point to the LRL fiel
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operating system for such a purpose
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position where the last character i
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ecord. If a file has more than four
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DE Contains a pointer to the File C
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@RENAM SVC-56 Rename a file on disk
Page 81 and 82: @FNAME SVC-80 Obtain filespec given
Page 83 and 84: @WRSEC SVC-53 Write a disk sector @
Page 85 and 86: 7.6 SUPERVISOR CALL DETAILS 7.6.1 @
Page 87 and 88: Note: @EXIT in SYS1 automatically r
Page 89 and 90: 7.6.10 @CLOSE SVC-60 This SVC will
Page 91 and 92: 7.6.18 @DCSTAT SVC-40 This SVC pass
Page 93 and 94: Directory to Buffer Entry: B 1; Fun
Page 95 and 96: 7.6.31 @FLAGS$ SVC-101 This SVC wil
Page 97 and 98: NFLAG$ This "network" flag is used
Page 99 and 100: 7.6.32 @FNAME SVC-80 This SVC will
Page 101 and 102: 7.6.40 @HEX8 SVC-98 This SVC will c
Page 103 and 104: 7.6.48 @KLTSK SVC-32 This SVC will
Page 105 and 106: 7.6.57 @OPEN SVC-59 This SVC will o
Page 107 and 108: Registers Affected: AF, BC. Entry:
Page 109 and 110: 0-14 FILENAME/EXT:D - left justifie
Page 111 and 112: 7.6.71 @REMOV SVC-57 This SVC will
Page 113 and 114: Entry: DE A pointer to the FCB cont
Page 115 and 116: Exit: A Error return code, if any.
Page 117 and 118: CURSOR CHARACTER Registers Affected
Page 119 and 120: Exit: A Will contain the error code
Page 121 and 122: esident routine into its execution
Page 123 and 124: CKPAWS LD A,@FLAGS$ ;Get Flags poin
Page 125 and 126: ===================================
Page 127 and 128: The TYPE=0A indicates that it is th
Page 129 and 130: Error 08: Device not available A re
Page 131: Error 28: End of file encountered T
Page 135 and 136: This is obviously an extremely usel
Page 137 and 138: LD (IX+2),15 JR TASKA By firmly und
Page 139 and 140: 8.7.3 Details of Low Memory Page 2
Page 141 and 142: actual bank switching. As previousl
Page 143 and 144: set. Thus, the Z-flag will be indic
Page 145 and 146: 8.10 SYSTEM DISK BOOT TRACK The ope
Page 147 and 148: 14 DEBUG 72 PURGE 1B VERIFY 71 DUMP
Page 149 and 150: 8.13 USING @PARAM The @PARAM SuperV
Page 151 and 152: DW LPARM+1 DB 'FEED ' ;Line feed pa
Page 153 and 154: ;*=*=* PPARM LD BC,0 ;Zero because
Page 155 and 156: 8.14 TRAP Filter Illustrated ;TRAP/
Page 157 and 158: 8.15 SLASH0 Filter Illustrated ;SLA
Page 159 and 160: 8.16 DMP-500 BOLDFACE Filter Illust
Page 161 and 162: NOMEM$ DB 'High memory is not avail
Page 163 and 164: @ @ABORT..........7-2, 7-4, 7-8, 7-
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