The GOFF (Generalized Object File Format) specification was developed for IBM's MVS operating system to supersede the IBM OS/360 Object File Format to compensate for weaknesses in the older format.[1]
The original IBM OS/360 Object File Format was developed in 1964 for the new IBM System/360 mainframe computer. The format was also used by makers of plug compatible and workalike mainframes, including the Univac 90/60, 90/70 and 90/80 and Fujitsu B2800. The format was expanded to add symbolic records and expanded information about modules, plus support for procedures and functions with names longer than 8 characters. While this helped, it did not provide for the enhanced information necessary for today's more complicated programming languages and more advanced features such as objects, properties and methods, Unicode support, and virtual methods.
The GOFF object file format was developed by IBM approximately in 1995 as a means to overcome these problems.[2] The earliest mention of this format was in the introductory information about the new High Level Assembler.[3] Note that the OS/360 Object File Format was simply superseded by the GOFF format, it was not deprecated, and is still in use by assemblers and language compilers where the language can withstand the limitations of the older format.
This article will use the term "module" to refer to any name or equivalent symbol, which is used to provide an identifier for a piece of code or data external to the scope to which it is referenced. A module may refer to a subroutine, a function, Fortran Common or Block Data, an object or class, a method or property of an object or class, or any other named routine or identifier external to that particular scope referencing the external name.
The terms "assembler" for a program that converts assembly language to machine code, as well as as the process of using one, and as the process of using a "compiler," which does the same thing for high-level languages, should, for the purposes of this article. be considered interchangeable; thus where "compile" and "compiler" are used, substitute "assemble" and "assembler" as needed.
Numbers used in this article are expressed as follows: unless specified as hexadecimal (base 16), all numbers used are in decimal (base 10). When necessary to express a number in hexadecimal, the standard mainframe assembler format of using the capital letter X preceding the number, expressing any hexadecimal letters in the number in upper case, and enclosing the number in single quotes, e.g. the number 15deadbeef16 would be expressed as X'15DEADBEEF'.
A "byte" as used in this article, is 8-bits, and unless otherwise specified, a "byte" and a "character" are the same thing; characters in EBCDIC are also 8-bit. When multi-byte character sets (such as Unicode) are used in user programs, they will use two (or more) bytes.
The format is similar to the OS/360 Object File Format but adds additional information for use in building applications.[4]
The following classes used by the binder may be referenced if needed for compilation purposes:
| width=20% | B_ESD | External Symbol Dictionary Class |
| B_TEXT | Text Class | |
| B_RLD | Relocation Dictionary Class | |
| B_SYM | Internal Symbol Table Class | |
| B_IDRL | Language-Translator Identification Data Class | |
| B_PRV | Pseudo-Register Class | |
| B_IDRU | User-specified Identification Data Class |
The following class names are reserved by the binder and are not accessible to user applications:
| B_IDRB | Binder Data Information | |
| B_IDRZ | SUPER-Zap Data Information | |
| B_IMPEXP | Import-Export Table | |
| B_LIT | Loading Information Table | |
| B_MAP | Mapping Data |
According to the Users Guide for z/OS XL C/C++ User's Guide, "The maximum size of a GOFF object is 1 gigabyte."[6]
Similarly to the older OS/360 format, object file records are divided into 6 different record types, some added, some deleted, some altered:
GOFF records may be fixed or variable length; the minimum length when using variable-length records is 56 characters, although most records will be longer than this. Except for module and class names, all characters are in the EBCDIC character set. Unix-based systems must use fixed-length (80-byte) records. Records in fixed-length files that are shorter than the fixed length should be zero-filled. To distinguish GOFF records from the older OS/360 object format (where the first byte of a record is X'02') or from commands that may be present in the file, the first byte of each GOFF record is always the binary value X'03', while commands must start with a character value of at least space (X'40'). The next 2 bytes of a GOFF record indicate the record type, continuation and version of the file format. These first 3 bytes are known as the PTV field.
The PTV field represents the first 3 bytes of every GOFF record.
| Bits | Value | Purpose | ||
|---|---|---|---|---|
| 0 | All | 03 | Indicates start of a GOFF record | |
| 1 | 0-3 | 0 | ESD (External Symbol) record | |
| 1 | TXT (Text) record | |||
| 2 | RLD (Relocation) record | |||
| 3 | LEN (Length) record | |||
| 4 | END (End) record | |||
| X'5'-X'E' | Reserved | |||
| X'F' | HDR (Header) record | |||
| 4-5 | Reserved | |||
| 6-7 | 00 | Initial record that is not continued on the next record. This should be the only value used for variable-length GOFF records | ||
| 01 | Initial record which is continued on next record | |||
| 10 | Continuation record not continued on next record | |||
| 11 | Continuation record which is continued on the next record | |||
| 2 | All | 00 | Version Number of the object file format. All values except X'00' are reserved |
The HDR record is required, and must be the first record.
| Size | Field | Value | Purpose | ||
|---|---|---|---|---|---|
| 0-2 | 3 | PTV | X'03F000' | Only allowed value; HDR record currently cannot be continued | |
| 3-47 | 45 | 0 | Reserved | ||
| 48-51 | 4 | Architecture Level | Binary 0 or 1 | GOFF Architecture level; all values except 0 and 1 are reserved | |
| 52-53 | 2 | Module Properties Size | binary | Length of Module Properties Field | |
| 54-59 | 6 | 0 | Reserved | ||
| 60- | 0+ | Module Properties | Module Properties List (optional) |
An ESD record gives the public name for a module, a main program, a subroutine, procedure, function, property or method in an object, Fortran Common or alternate entry point. An ESD record for a public name must be present in the file before any reference to that name is made by any other record.
| Size | Field | Value (or bits) | Purpose | |||
|---|---|---|---|---|---|---|
| 0-2 | 3 | PTV | X'030000' | ESD record with no continuations | ||
| X'030100' | ESD record which is continued on next record | |||||
| 3 | 1 | Symbol Type | 00 | SD - Section Definition; This is used for the former SD, CM (Common) and PC (Private Code, an SD whose name is blank) values. The "Parent" ESDID value must be 0. This is used to define a main program, a subroutine or function for which the code is part of this file. Also used for Fortran Common. | ||
| 01 | ED - External Definition. "Parent" ESDID must be non-zero, and be the value of an SD entry that references this external symbol. If an RLD value refers to a class this entry belongs to, the Class that this element refers to must be specified in the External Name field. This is used to name a called procedure or function. | |||||
| 02 | LD - Label Definition. "Parent" ESDID must be non-zero, and be the value of an SD entry that defines this symbol within itself. This can be used to create an alias for the module or to expose a portion of it as a separate routine. For example, the run-time library for a particular programming language might have certain features it has to use itself, but which are useful by programs written using that language, and so a feature could be given a label so it can be called directly. For example, there may be a complete mathematics package as a single module, and all of the standard functions (Sine, Cosine, Square Root, etc.) could be named entry points in that module. | |||||
| 03 | PR - Part Reference or Pseudo Register. Distinguished by Name Space ID field. "Parent" ESDID must be non-zero, and be the value of an SD entry that defines this symbol within itself. | |||||
| 04 | ER and WX - External Reference / Weak External Reference. Distinguished between by the "Binding Strength" value of the "Attributes" field. WX is used where the foreign routine may be missing. For example, if a calculator program had a fast high-performance math package that was optional, it could be called as a WX, and if it was missing or not available, the program could downgrade to a lesser math package. | |||||
| 4-7 | 4 | ESDID | Binary | ESDID identifier starting with 1. Each new ESDID must be exactly 1 higher than the previous entry. | ||
| 8-11 | 4 | Parent ESDID | binary | This is the ESDID of the object that defines this entry, if it is part of another object. It is 0 if it has no parent. | ||
| 12-15 | 4 | 0 | Reserved | |||
| 16-19 | 4 | Offset | Binary | Address of this symbol within its Parent ESDID for LD or ED entries; zero otherwise. | ||
| 20-23 | 4 | 0 | Reserved | |||
| 24-27 | 4 | Length | Binary | Length of this item for ED and PR types; zero otherwise. If the actual length value is deferred; this value is set to -1. | ||
| 28-31 | 4 | Extended Attribute ESDID | Binary | ESDID of element that contains extended attribute information for ED and LD types; typically used where DLLs are supported for symbols which are resolved at run time (like virtual methods). Zero otherwise. | ||
| 32-35 | 4 | Extended Attribute Offset | Binary | Address where extended attributes can be found for the previous field, used for ED and LD records having extended attributes; zero otherwise. | ||
| 36-39 | 4 | 0 | Reserved | |||
| 40 | 1 | Name Space ID | Identifies the name space this belongs to | |||
| 0 | Reserved for Program Management Binder | |||||
| 1 | Normal Name | |||||
| 2 | Pseudo Register | |||||
| 3 | Parts (External entries allocated space including items containing initialized static data) | |||||
| 41 | 1 | Flags | ||||
| Fill Present | Bit 0 | 0 | No Fill | |||
| 1 | Fill Byte Present (only valid for ED types) | |||||
| Mangled | Bit 1 | 0 | Symbol is not mangled | |||
| 1 | Symbol may be mangled | |||||
| Renameable | Bit 2 | 0 | Cannot be renamed (same as 'mapped' flag in XOBJ) | |||
| 1 | Symbol can be renamed (Can participate in Language Environment (LE) type renaming) | |||||
| Removable Class | Bit 3 | 0 | (Default) Not Removable | |||
| 1 | This Class can optionally be deleted without affecting the program's operation (Only valid for ED types) | |||||
| Bits 4-6 | Reserved | |||||
| Reserve Extra Space | Bit 7 | 0 | No Extra Space Reserved | |||
| 1 | Reserve 16 bytes of space at the beginning of the Class (MRG class ED type only) | |||||
| 42 | 1 | Fill Value | Value of Fill byte, if Fill Present flag is set | |||
| 43 | 1 | 0 | Reserved | |||
| 44-47 | 4 | Associated Data | Binary | Used for ID of environment or static area for LD items using XLINK | ||
| 48-51 | 4 | Priority | Binary | Sort order of PR items | ||
| 52-59 | 8 | 0 | Reserved | |||
| 60-69 | 10 | Behavioral Attributes | Behavior Attributes for this item (See Behavior Attributes table below) | |||
| 70-71 | 2 | Name Length | Binary | Length of this item's name; cannot be zero | ||
| 72- | Name | Text | Name of this item with trailing blanks truncated. Must be at least one character; Private Code consists of a single blank. Name is case sensitive. | |||
| REM | 0 | Trailer: Unused space if needed for fixed-size records; must be zero filled. Not needed in variable-length records. | ||||
In the case of fixed-length records where the name requires continuation records, the following is used:
| Size | Field | Value | Purpose | |||
|---|---|---|---|---|---|---|
| 0-2 | 3 | PTV | X'030200' | ESD continuation record with no further continuations | ||
| X'030300' | ESD continuation record which is continued on next record | |||||
| 3- | Name | Text | The rest of the name if this record is not continued, or the next 77 bytes of the name if continued. | |||
| REM | 0 | Remainder for a fixed-length record longer than the data supplied. It contains the trailing bytes if this is the last record for this name and the name is shorter than the record size; must be 0 filled. This field is not present in variable-length records. | ||||
| Size (Bytes) | Bits | Field | Value | Purpose | |||||
|---|---|---|---|---|---|---|---|---|---|
| 0 | 1 | Addressing Properties | Addressing mode associated with this external symbol. These values are also used by the AMODE field of the END record. | ||||||
| 00 | AMODE not specified (defaults to AMODE (24)) | ||||||||
| 01 | AMODE(24) | ||||||||
| 02 | AMODE(31) | ||||||||
| 03 | AMODE(ANY) (24 or 31) | ||||||||
| 04 | AMODE(64) | ||||||||
| 10 | AMODE(MIN) (Use the smallest AMODE used by all modules) | ||||||||
| 1 | 1 | Residence Properties | External Symbol's Associated Residence Mode | ||||||
| 00 | RMODE not specified (defaults to RMODE (24)) | ||||||||
| 01 | RMODE(24) | ||||||||
| 03 | RMODE(31) (Equivalent to RMODE(ANY)) | ||||||||
| 04 | RMODE(64) | ||||||||
| 2 | 1 | 0-3 (4) | Text Record Style | Style of text for this class (ED and PR types only) All text must be the same style | |||||
| 0000 | Byte-oriented | ||||||||
| 0001 | Structured data (Binder Oriented) | ||||||||
| 0010 | Structured data (user defined) | ||||||||
| 4-7 (4) | Binding Algorithm | Data Binding Method | |||||||
| 0000 | Concatenate all items one after another | ||||||||
| 0001 | Merge (all identically named items will be located at the same space, using the largest size specified, and most restrictive alignment). Differently named items will be concatenated. This is the usual practice for CM and PR types. | ||||||||
| 3 | 1 | 0-2 (3) | Tasking Behavior | Indication whether module is reentrant and/or reusable | |||||
| 000 | Unspecified | ||||||||
| 001 | Neither Reusable nor Reentrant (NON-REUS) | ||||||||
| 010 | Serially Reusable (REUS) | ||||||||
| 011 | Reentrant (RENT), also implies (REUS) | ||||||||
| 3 | 0 | Reserved | |||||||
| 4 | Read Only | 0 | Not Read Only | ||||||
| 1 | Read Only | ||||||||
| 5-7 (3) | Executable | 000 | Not Specified | ||||||
| 001 | Not Executable (Data only) | ||||||||
| 010 | Executable (Code or Code and data) | ||||||||
| 4 | 1 | 0-1 (2) | 0 | Reserved | |||||
| 2-3 (2) | Duplicate Symbol Severity | Level of error a duplicate symbol should raise (PR type records only) | |||||||
| 00 | Binder determines severity | ||||||||
| 01 | Minimum 4 (Warning) | ||||||||
| 10 | Minimum 8 (Error) | ||||||||
| 11 | Reserved | ||||||||
| 4-7 (4) | Binding Strength | Weak references will not search other libraries; Strong references will search other libraries for the symbol. Strong Definitions can be resolved to any reference; this is the default. | |||||||
| 0000 | Strong | ||||||||
| 0001 | Weak | ||||||||
| 5 | 1 | 0-1 (2) | Class Loading Behavior | Determines whether the elements of a class will be loaded in the case of an Operating System LOAD request is used with respect to an object | |||||
| 00 | LOAD - Load this class | ||||||||
| 01 | DEFERRED LOAD - This class will probably be used and should be loaded | ||||||||
| 10 | NOLOAD - Do not load this class | ||||||||
| 11 | Reserved | ||||||||
| 2 | Common Flag | If 1, treat as "old" CM-type COMMON where multiple references set the size to the largest area being used by any reference. An SD type with the same name will keep the size and text. The only text type supported for this is B_TEXT. | |||||||
| 3 | Direct vs. Indirect Reference | 0 | Direct References (for purposes of the Binder) | ||||||
| 1 | For PR type, this is a linkage descriptor; for ER type, this is a reference to an XPLINK linkage descriptor | ||||||||
| 4-7 (4) | Binding Scope | 0000 | Unspecified | ||||||
| 0001 | Section scope (“local”) | ||||||||
| 0010 | Module scope (“global”) | ||||||||
| 0011 | Library scope | ||||||||
| 0100 | Import-Export scope | ||||||||
| 6 | 1 | 0-1 (2) | Reserved | ||||||
| 2 | Linkage Type | For ER, LD, PD, and PR types | |||||||
| 0 | Standard O/S linkage (default) | ||||||||
| 1 | XPLINK Linkage | ||||||||
| 3-7 (5) | Alignment | Implied Alignment of this item | |||||||
| 00000 | Byte | ||||||||
| 00001 | Halfword | ||||||||
| 00010 | Fullword | ||||||||
| 00011 | Doubleword | ||||||||
| 00100 | Quadword | ||||||||
| 00101 | 4KB page | ||||||||
| All alignments shown are available for ED and PR types except PR cannot use page alignment | |||||||||
| 7-9 | 3 | Reserved | |||||||
ADATA ("associated data") records are used to provide additional symbol information about a module. They replaced the older SYM records in the 360 object file format. To create an ADATA record
ADATA records will be appended to the end of the class in the order they are declared.
Class names assigned to ADATA records are translated by IBM programs by converting the binary value to text and appending it to the name C_ADATA, So an item numbered X'0033' would become the text string C_ADATA0033.
| TYpe | Description | |
| Translator records (note that some values in the range 0-X'0130' are in use by some IBM language translator products including Assembler, Cobol and PL/I). | ||
| Program Management records | ||
| Reserved | ||
| Reserved for compilers and assemblers not released by IBM. | ||
| Available for User Records. IBM will not use these values. |
TXT records specify the machine code instructions and data to be placed at a specific address location in the module. Note that wherever a "length" must be specified for this record, the length value must include any continuations to this record.
| Size | Field | Bits | Value | Purpose | ||
|---|---|---|---|---|---|---|
| 0-2 | 3 | PTV | X'031000' | TXT record with no continuations | ||
| X'031100' | TXT record which is continued on next record | |||||
| 3 | 1 | 0-3 (4) | Reserved | |||
| Style | 4-7 (4) | All other values are reserved | ||||
| 0000 | Byte Oriented Data | |||||
| 0001 | Structured Data (currently the only structured data supported are the 19-byte IDR fields; see IDR Data Table) | |||||
| 0010 | Unstructured Data | |||||
| 4-7 | 4 | Element ESDID | Binary number | ESDID that the contents of this record belong to | ||
| 8-11 | 4 | Reserved | ||||
| 12-15 | 4 | Offset | Binary address | Address within ESDID where this data is to be placed. This should be 0 for structured and unstructured data. | ||
| 16-19 | 4 | Text field true length | binary value: 0 or full size after expansion | If Text Encoding field is 0, this must be 0. Otherwise this field is the full size of the text after decompression or unpacking | ||
| 20-21 | 2 | Text Encoding | binary value | 0 if text does not require replication, unpacking, or decoding; nonzero to indicate text must be decoded, unpacked or expanded; see Compression Table | ||
| 22-23 | 2 | Data Length | binary value greater than zero | Total length of the data on this record in bytes as an unsigned value, and cannot be zero, however, this may be partially incorrect, as noted below in Caution. | ||
| 24- | Data | Machine code and/or data to be inserted. If IDR data is included it is subject to special rules and requirements, see IDR Data Table | ||||
| REM | Not present for variable-length records; remainder bytes for fixed record longer than remaining data, and must be binary zeroes | |||||
The data length in bytes 22-23 being an unsigned value may be incorrect. According to comments in the GOFF generator part of the LLVM Compiler suite,
"The maximum number of bytes that can be included in an RLD or TXT record and their continuations is a SIGNED 16 bit int despite what the spec says. The number of bytes we allow ourselves to attach to a card is thus arbitrarily limited to 32K-1 bytes."[7]
| Size | Field | Bits | Value | Purpose | |
|---|---|---|---|---|---|
| 0-2 | 3 | PTV | X'031200' | Continuation Record with no further continuations | |
| X'031300' | Continuation Record which is continued next record | ||||
| 3- | Data continued from previous record | ||||
| REM | If remainder of record is longer than data; zero filled | ||||
A compression table is used if bytes 20-21 of the TXT record is nonzero. The R value is used to determine the number of times to repeat the string; the L value indicates the length of the text to be repeated "R" times. This could be used for pre-initializing tables or arrays to blanks or zero or for any other purpose where it is useful to express repeated data as a repeat count and a value.
| Size | Field | Value | Purpose | ||
|---|---|---|---|---|---|
| If value in bytes 20-21 of this TXT record is 0001 | |||||
| 0-1 | 2 | R | Repeat Count, an unsigned integer greater than 0 | Number of times to repeat the string starting in byte 4. | |
| 2-3 | 2 | L | Binary length, an unsigned integer greater than 0 | Length of string starting in byte 4 | |
| 4- | String | The string, of length "L" which is to be repeated "R" times. | |||
| All other values for bytes 20-21 are reserved | |||||
The IDR Table, which is located starting at byte 24 of the TXT record, identifies the compiler or assembler (and its version number) that created this object file.
| Size | Field | Value | Purpose | |
|---|---|---|---|---|
| 0 | 1 | x'00' | Reserved | |
| 1 | 1 | Type | Type of IDR field (note that Primary and Secondary identification refers to the first and second identification fields, respectively, appearing on the END card in the former OS/360 Object Module File Format.) | |
| 00 | Primary Identification; Old IDR format 1 | |||
| 01 | Secondary Identification; Old IDR format 1 | |||
| 02 | Extended Identification; IDR format 2 | |||
| 03 | Primary Identification; IDR format 3 | |||
| 04 | Secondary Identification; IDR format 3 | |||
| 2-3 | 2 | Length | Binary number | Length of IDR data as unsigned integer greater than zero |
| 4+ | IDR data according to the specified format in byte 1 of this field; see the appropriate IDR Format table for details | |||
Note that unlike most number values stored in a GOFF file, the "version", "release" and "trans_date" values are numbers as text characters instead of binary
| Size | Field | Value | Purpose | |
|---|---|---|---|---|
| 0-9 | 10 | Translator | Any text | This value is what the assembler or compiler identifies itself as; IBM calls this the "PID value" or "Program ID value" from IBM's catalog numbers of various programs, e.g. the Cobol Compiler for OS/VS1 is called "IKFCBL00" |
| 10-11 | 2 | Version | two digits | This is the version number of the assembler or compiler, 0 to 99. |
| 12-13 | 2 | Release | two digits | This is the release number subpart of the version number above, also 0 to 99 |
| 14-18 | 5 | Trans_Date | YYDDD | 5 text characters indicating the 2-digit year, and the 3-digit day of the year this module was compiled or assembled; years 01-65 are presumed to be in the 21st Century, while year 00 or years greater than 65 are presumed to be in the 20th Century, e.g. 2000 or 1966-1999. The three digit day starts at 001 for January 1; 032 for February 1; 060 is March 1 in standard years and February 29 in leap years; and continuing through 365 for December 31 in standard years and 366 for leap years. |
Normally compilers and assemblers do not generate this format record, it is typically created by the binder.
| Size | Field | Value | Purpose | |
|---|---|---|---|---|
| 0-3 | 4 | Date | Packed decimal form YYYYDDDF | Date module was assembled or compiled, with the year and day of the year |
| 4-5 | 2 | Data_Length | Binary value | Actual length of next field, an unsigned, nonzero value |
| 6-85 | 80 | IDR_Data | Format of this data has not been disclosed | |
All text in this item are character data; no binary information is used.
| Size | Field | Value | Purpose | |
|---|---|---|---|---|
| 0-9 | 10 | Translator | Any text value the compiler/assembler writer wishes to use to identify itself (see the Translator field in old IDR Format 1 above) | |
| 10-11 | 2 | Version | 00 to 99 | Version number of the assembler or compiler |
| 12-13 | 2 | Release | 00 to 99 | Release number of above version |
| 14=20 | 7 | Compile_Date | YYYYDDD | Year and day of year the program was compiled or assembled (this would be the same format as the 'Trans Date' field from IDR Format 1 above, except the year is a full 4-digit year). |
| 21-29 | 9 | Compile_Time | HHMMSSTTT | Hour, minute, second and thousandth of second that the program was compiled or assembled |
RLD records allow a module to show where it references an address that must be relocated, such as references to specific locations in itself, or to external modules.
| Size | Field | Value | Purpose | |
|---|---|---|---|---|
| 0-2 | 3 | PTV | X'032000' | Record is not continued |
| X'032100' | Record continues on next record | |||
| 3 | 1 | Reserved | ||
| 4-5 | 2 | Length | Binary Number | Size of relocation data; unsigned and must be greater than zero |
| 6- | Relocation_Data | The relocation data; see Relocation Data table | ||
| REM | Not present on variable-length records; remainder of record where record is longer than data, must be zero-filled | |||
| Size | Field | Value | Purpose | ||
|---|---|---|---|---|---|
| 0-5 | 6 | Flags | Flags regarding this entry; see Flags table for values | ||
| 6-7 | 2 | colspan-4 | Reserved | ||
| 8-11 | 4 | R_Pointer | ESDID of module (type ED or ER) to use as the target to relocate | This is the "distant" address, either in the same or a different module, that the program needs resolved. This field is omitted if bit 0 of byte 0 of the Flags field is 1. | |
| 12-15[A] | 4 | P_Pointer | ESDID of module that requires the address to be relocated | This is the module that wants its reference to a distant identifier to be altered to the correct value. This field is omitted if bit 1 of byte 0 of the Flags field is 1. | |
| 16-19[B] | 4 | Offset | Location within module specified by P_Pointer where the address to be adjusted is to be found. | This is the address to be relocated. This field is omitted if bit 2 of byte 0 of the Flags field is 1. | |
| 20-23[C] | 4 | Reserved | |||
| 24-27[C] | 4 | Reserved | |||
To clarify, if a module in a C program named "Basura" was to issue a call to the "exit" function to terminate itself, the R_Pointer address would be the ESDID of the routine "exit" while the P_Pointer would be the ESDID of "Basura". If the address was in the same module (like internal subroutines, or a reference to data within the same module) R_Pointer and P_Pointer would be the same.
| Size | Field | Bits | Purpose | ||
|---|---|---|---|---|---|
| 0 | 1 | Same_R_ID | 0 | 1 If the R_Pointer value for this entry is the same as the previous item in this record; if so, the R_Pointer value is omitted from this entry. | |
| Same_P_ID | 1 | 1 If the P_Pointer value for this entry is the same as the previous item in this record; if so, the P_Pointer value is omitted from this entry. | |||
| Same_Offset | 2 | 1 If the Offset value for this entry is the same as the previous item in this record; if so, the Offset value is omitted from this entry. | |||
| 3-4 | Reserved | ||||
| 5 | Reserved | ||||
| Offset_length | 6 | 0 to indicate 4 byte length | |||
| Addressing mode sensitivity | 7 | 0 No Sensitivity | |||
| 1 Set the high bits of the address to the same as the R mode addressing mode of the R_Pointer address (applies only to V-type addresses) | |||||
| 1 | 1 | R_Pointer_Indicators | 0-3 | Data Type of Second Operand of relocation address | |
| 0 - R-address | |||||
| 1 - Offset from start of R-address | |||||
| 2 - R-Length (0 for LD items) | |||||
| 6 - Relative immediate (to allow instructions to address external symbols) | |||||
| 7 - R Constant (nonshared data area) | |||||
| 9 - 20-Bit long displacement address | |||||
| All other values are reserved | |||||
| 4-7 | Type of item referring to the value needing to be relocated. | ||||
| 0 - Label, R-ID is restricted to LD | |||||
| 1 - Element, R-ID is restricted to ED | |||||
| 2 - Class, R-ID is restricted to ED; Classes do not have external names so they do not have an ESDID | |||||
| 3 - Part, R-ID is restricted to PR | |||||
| All other values are reserved | |||||
| 2 | 1 | Action_or_Operation | 0-6 | Type of operation to use with second operand (the first operand would be 0) the result is a 32-bit signed value which replaces the first operand | |
| 0 - Add second operand to first | |||||
| 1 - Subtract second operand from first | |||||
| All other values are reserved | |||||
| Fixup Target Fetch/Store | 7 | Indicates whether to use or ignore target value | |||
| 0 - Use fixup/target field as first operand | |||||
| 1 - Ignore value of target field use fixup value as first operand; if no fixup value, use 0 | |||||
| 3 | 1 | Reserved | |||
| 4 | 1 | Target Length | Unsigned length of target field in bytes | ||
| 5 | 1 | Reserved | |||
LEN records are used to declare the length of a module where it was not known at the time the ESD record was created, e.g. for one-pass compilers.
| Field | Offset | Size | Description | |
| PTV | 0-2 | 3 | Record Type X'033000' | |
| 3-5 | 3 | Reserved | ||
| Length | 6-7 | 2 | Length of items following this field; value must be non-zero | |
| Elements | 8- | Element length data; see Elements table below | ||
| REM | Trailing data to end of record for fixed-length records, must contain binary zeroes; not present for variable-length records. |
A deferred-length element entry cannot be continued or split
| Field | Offset | Size | Description |
| ESDID | 0-3 | 4 | ESDID of element this value applies to |
| 4-7 | 4 | Reserved | |
| Length | 8-11 | 4 | Length of the item referenced |
END must be the last record for a module. An 'Entry Point' is used when an address other than the beginning of the module is to be used as the start point for its execution. This is used either because the program has non-executable data appearing before the start of the module (very common for older assembly programmers, as older versions of the assembler were much slower to assemble data stored in programs once instructions were specified), or because the module calls an external module first, such as a run-time library to initialize itself.
| Field | Offset | Size | Bits | Description | |
| PTV | 0-2 | 3 | X'034000' - Not-continued | ||
| X'034100' - Continued on next record | |||||
| 3 | 0-5 | 6 | Reserved | ||
| Flags | 6-7 | 2 | Declarations regarding the presence or absence of an entry point | ||
| 00 - No entry point given; all other values in this record are invalid | |||||
| 01 - Entry point specified by ESDID | |||||
| 10 - Entry point specified by name | |||||
| 11 - Reserved | |||||
| AMODE | 4 | 1 | Addressing Mode value of entry point; the values are as specified in field 0 of the Behavior Attributes table in the ESD record. | ||
| 5-7 | 3 | Reserved | |||
| Record Count | 8-11 | 4 | Number of GOFF records in this module (this is the number of "logical" records, i.e. not counting continuations) | ||
| ESDID | 12-15 | 4 | Value of ESDID if entry point is referenced by ESDID; binary zero if referenced by name | ||
| 16-19 | 4 | Reserved | |||
| Offset | 20-23 | 4 | Address offset of module entry point; this cannot be specified for an external (ER) entry point | ||
| Name Length | 24-25 | 2 | Length of name, this must be zero if entry point was specified by ESDID. | ||
| Name | 26- | The name of the external symbol used as the entry point for this module; is binary zeros if entry point was specified by ESDID; if this record is continued this is the initial 54 characters of the name. This is the only non-binary value in the record; it would be a text field representing the public name for the entry point | |||
| REM | Trailer extending to the end of the record; should be binary zeros to end of record for fixed-length records; omitted for variable-length |
If an entry-point name specified on a fixed-length END record is longer than 54 bytes or (if this record itself is also continued) is longer than an additional 77 bytes), the following continuation record is used.
| Field | Offset | Size | Description | |
| PTV | 0-2 | 3 | X'034200' - This continuation record is not-continued | |
| X'034300' - This continuation record is itself continued on the next record | ||||
| Name | 3- | The remaining part of the entry-point name, unless this record is continued, in which case it is the next 77 characters of the name. | ||
| REM | If this record is not continued, this is the trailing part of the record for fixed-length records and should be binary zeroes; not present for variable-length records | |||