Intel hexadecimal object file format,Intel hex format orIntellec Hex is afile format that conveysbinary information inASCIItext form,^[10] making it possible to store on non-binary media such aspaper tape,punch cards, etc., to display ontext terminals or be printed online-oriented printers.^[11] The format is commonly used for programmingmicrocontrollers,EPROMs, and other types of programmable logic devices andhardware emulators. In a typical application, acompiler orassembler converts aprogram'ssource code (such as inC orassembly language) tomachine code and outputs it into anobject orexecutable file in hexadecimal (or binary) format. In some applications, the Intel hex format is also used as acontainer format holdingpackets ofstream data.^[12] Common file extensions used for the resulting files are .HEX^[1] or .H86.^[5][6] The HEX file is then read by aprogrammer to write the machine code into aPROM or is transferred to the target system for loading and execution.^[11][13] There are various tools to convert files between hexadecimal and binary format (i.e.HEX2BIN), and vice versa (i.e. OBJHEX, OH, OHX, BIN2HEX).

The Intel hex format was originally designed forIntel'sIntellec Microcomputer Development Systems^{[14]: 10–11} (MDS) in 1973 in order to load and execute programs frompaper tape. It was also used to specify memory contents to Intel forROM production,^[15] which previously had to beencoded in the much less efficientBNPF (Begin-Negative-Positive-Finish) format.^[14]: 11 In 1973, Intel's "software group" consisted only of Bill Byerly and Kenneth Burgett, andGary Kildall as an external consultant doing business asMicrocomputer Applications Associates (MAA) and foundingDigital Research in 1974.^{[16][17][18][9]} Beginning in 1975, the format was utilized byIntellec Series IIISIS-II systems supporting diskette drives, with files using the file extension HEX.^[19] ManyPROM andEPROM programming devices accept this format.

Intel HEX consists of lines ofASCII text that are separated byline feed orcarriage return characters or both. Each text line contains uppercasehexadecimal characters thatencode multiple binary numbers. The binary numbers may represent data,memory addresses, or other values, depending on their position in the line and the type and length of the line. Each text line is called arecord.

Arecord (line of text) consists of sixfields (parts) that appear in order from left to right:^[11]

1. Start code, one character, an ASCII colon ':'. All characters preceding this symbol in a record should be ignored.^{[15][5][20][21][22][23]} In fact, very early versions of the specification even asked for a minimum of 25NUL characters to precede the first record and follow the last one, owing to the format's origins as apaper tape format which required sometape leadin and leadout for handling.^{[15][24][21][22]} However, as this was a little known part of the specification, not all software written copes with this correctly. It allows to store other related information in the same file (and even the same line),^[15][23] a facility used by various software development utilities to storesymbol tables or additional comments,^{[25][15][21][26][9][27]} and third-party extensions using other characters as start code like the digits '0'..'9' by Intel^[28] andKeil,^[26] '$' byMostek,^[29][30] or '!', '@', '#', '\', '&' and ';' byTDL.^[30][31] By convention, '//' is often used for comments.^[32][33] Neither of these extensions may contain any ':' characters as part of the payload.
2. Byte count, two hex digits (one hex digit pair), indicating the number of bytes (hex digit pairs) in the data field. The maximum byte count is 255 (0xFF). The values of 8 (0x08),^[9] 16 (0x10)^[9] and 32 (0x20) are commonly used byte counts. Not all software copes with counts larger than 16.^[2]
3. Address, four hex digits, representing the 16-bit beginning memory address offset of the data. Thephysical address of the data is computed by adding this offset to a previously establishedbase address, thus allowing memory addressing beyond the 64 kilobyte limit of 16-bit addresses. The base address, which defaults to zero, can be changed by various types of records. Base addresses and address offsets are always expressed asbig endian values.
4. Record type (seerecord types below), two hex digits,00 to05, defining the meaning of the data field.
5. Data, a sequence ofn bytes of data, represented by 2n hex digits. Some records omit this field (n equals zero). The meaning and interpretation of data bytes depends on the application. (4-bit data will either have to be stored in the lower or upper half of the bytes, that is, one byte holds only one addressable data item.^[15])
6. Checksum, two hex digits, a computed value that can be used to verify the record has no errors.

As a visual aid, the fields of Intel HEX records are colored throughout this article as follows:

  Start code  Byte count  Address  Record type  Data  Checksum

A record's checksum byte is thetwo's complement of theleast significant byte (LSB) of the sum of all decoded byte values in the record preceding the checksum. It is computed by summing the decoded byte values and extracting the LSB of the sum (i.e., the data checksum), and then calculating the two's complement of the LSB (e.g., byinverting its bits and adding one).

For example, in the case of the record:0300300002337A1E, the sum of the decoded byte values is03 +00 +30 +00 +02 +33 +7A =E2, which has LSB valueE2. The two's complement ofE2 is1E, which is the checksum byte appearing at the end of the record.

The validity of a record can be checked by computing its checksum and verifying that the computed checksum equals the checksum appearing in the record; an error is indicated if the checksums differ. Since the record's checksum byte is the two's complement — and therefore theadditive inverse — of the data checksum, this process can be reduced to summing all decoded byte values, including the record's checksum, and verifying that the LSB of the sum is zero. When applied to the preceding example, this method produces the following result:03 +00 +30 +00 +02 +33 +7A +1E =100, which has LSB value00.

Intel HEX records are usually separated by one or more ASCII line termination characters so that each record appears alone on a text line. This enhances readability by visuallydelimiting the records and it also provides padding between records that can be used to improve machineparsing efficiency. However, the line termination characters are optional, as the ':' is used to detect the start of a record.^{[15][5][24][20][21][22][23]}

Programs that create HEX records typically use line termination characters that conform to the conventions of theiroperating systems. For example, Linux programs use a single LF (line feed, hex value0A) character to terminate lines, whereas Windows programs use a CR (carriage return, hex value0D) followed by a LF.

Intel HEX has six standard record types:^[11]

Other record types have been used for variants, including06 ('blinky' messages / transmission protocol container) by Wayne and Layne,^[34]0A (block start),0B (block end),0C (padded data),0D (custom data) and0E (other data) by theBBC/Micro:bit Educational Foundation,^[35] and81 (data incode segment),82 (data indata segment),83 (data instack segment),84 (data inextra segment),85 (paragraph address for absolute code segment),86 (paragraph address for absolute data segment),87 (paragraph address for absolute stack segment) and88 (paragraph address for absolute extra segment) byDigital Research.^[6][20]

The original 4-bit/8-bitIntellec Hex Paper Tape Format andIntellec Hex Computer Punched Card Format in 1973/1974 supported only one record type00.^[36][37][25] This was expanded around 1975^[when?] to also support record type01.^[15] Sometimes calledsymbolic hexadecimal format,^[38] it could include an optional header containing asymbol table forsymbolic debugging,^{[25][28][26][9]} all characters in a record preceding the colon are ignored.^[15][5]

Around 1978^[when?], Intel introduced the new record types02 and03 (to add support for the segmented address space of the then-new8086/8088 processors) in theirExtended Intellec Hex Format.^[when?]

Special names are sometimes used to denote the formats of HEX files that employ specific subsets of record types. For example:

• I8HEX (akaHEX-80) files use only record types00 and01
• I16HEX (akaHEX-86) files use only record types00 through03^[10]
• I32HEX (akaHEX-386) files use only record types00,01,04, and05

This example shows a file that has four data records followed by an end-of-file record:

:10010000214601360121470136007EFE09D2190140:100110002146017E17C20001FF5F16002148011928:10012000194E79234623965778239EDA3F01B2CAA7:100130003F0156702B5E712B722B732146013421C7:00000001FF

  Start code  Byte count  Address  Record type  Data  Checksum

Besides Intel's own extension, several third-parties have also defined variants and extensions of the Intel hex format, includingDigital Research (as in the so-called "Digital Research hex format"^[6][20]),Zilog,Mostek,^[29][30]TDL,^[30][31]Texas Instruments,Microchip,^[39][40]c't, Wayne and Layne,^[34] andBBC/Micro:bit Educational Foundation (with its "Universal Hex Format"^[35]). These can have information onprogram entry points andregister contents, aswapped byte order in the data fields,fill values for unused areas,fuse bits, and other differences.

The Digital Research hex format for 8086 processors supports segment information by adding record types to distinguish between code, data, stack, and extra segments.^[5][6][20]

Most assemblers forCP/M-80 (and alsoXASM09 for theMotorola 6809) don't use record type 01h to indicate the end of a file, but use a zero-lengthdata type 00h entry instead.^[41][1] This eases the concatenation of multiple hex files.^[42][43][1]

Texas Instruments defines a variant where addresses are based on the bit-width of a processor's registers, not bytes.

Microchip defines variants INTHX8S^[44] (INHX8L,^[1] INHX8H^[1]), INHX8M,^[44][1][45] INHX16^[44] (INHX16M^[1]) and INHX32^[46] for theirPIC microcontrollers.

Alfred Arnold's cross-macro-assembler AS,^[1] Werner Hennig-Roleff's8051-emulator SIM51,^[26] and Matthias R. Paul's cross-converter BINTEL^[47] are also known to define extensions to the Intel hex format.

• Binary-to-text encoding, a survey and comparison of encoding algorithms
• Text-based protocol
• MOS Technology file format
• Motorola S-record hex format
• Tektronix hex format
• Texas Instruments TI-TXT (TI Text)
• Intel Micro Computer Set (MCS)
• Object file

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• "How Do I Interpret Motorola S & Intel HEX Formatted Data? Intel Hex-32, Code 99".Home > Hardware > … > In-circuit Test Systems > Automated Test Equipment [Discontinued] > Details.Keysight Technologies. Archived fromthe original on 2020-03-01. Retrieved2020-03-01.
• Bergmans, San (2019-06-02) [2001]."Intel HEX Format".SB-Projects. Archived fromthe original on 2020-03-01. Retrieved2020-03-01.
• Beard, Brian (2016) [2007]."Intel HEX-record Format".Lucid Technologies.Archived from the original on 2020-02-28. Retrieved2020-02-28.
• Anderson, Thomas N. (February 1998). "Intel Hex Word Address Object Format".The Telemark Assembler (TASM) User's Manual(PDF). 3.1. Issaquah, Washington, USA: Squak Valley Software. pp. 25–26.Archived(PDF) from the original on 2021-12-11. Retrieved2021-12-11.Intel Hex Word Address Object Format […] This format is identical to the Intel Hex Object Format except that the address for each line of object code is divided by two thus converting it to a word address (16 bit word). All other fields are identical. Here is an example: […] :180800000102030405060708090A0B0C0D0E0F101112131415161718AC […] :02080C00191AA3 […] :00000001FF […] (32 pages)
• "ADuC70xx Serial Download Protocol"(PDF) (Application Note). Revision C. Norwood, Massachusetts, USA:Analog Devices. 2016. AN-724.Archived(PDF) from the original on 2023-10-05. Retrieved2023-10-05. (8 pages)

• binex - a converter between Intel HEX and binary for Windows.
• SRecord, a converter between Intel HEX and binary for Linux (usage), C++ source code.
• kk_ihex, open source C library for reading and writing Intel HEX
• libgis, open source C library that converts Intel HEX, Motorola S-Record, Atmel Generic files.
• bincopy is a Python package for manipulating Intel HEX files.
• SwiftIntelHex - a Swift package to parse Intel HEX files for iOS and macOS.

• Binary-to-text encoding formats
• Embedded systems
• Computer file formats

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