Magic number (programming)
magic numbermagic numbersMagic debug values0xDEADBEEFCAFEBABEmagicmagic ASCII stringmagic constantmagic debug valuemagic string
In computer programming, the term magic number has multiple meanings.wikipedia
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file signaturesignature or ''magic'' number
Such signatures are also known as magic numbers or Magic Bytes.
Test Driven Developmenttest-first developmentTDD
Thus, declaring is better than several occurrences of the 'magic value' in a test suite.
animated GIF.gifGraphics Interchange Format
The two versions can be distinguished by looking at the first six bytes of the file (the "magic number" or signature), which, when interpreted as ASCII, read "GIF87a" and "GIF89a", respectively.
The term magic number or magic constant refers to the anti-pattern of using numbers directly in source code.
UFSBerkeley Fast File SystemFFS
MZDOS executableDOS .EXE files
The file can be identified by the ASCII string "MZ" (hexadecimal: 4D 5A) at the beginning of the file (the "magic number").
Microsoft compilers and interpreters, and many pieces of software on Microsoft Windows such as Notepad treat the BOM as a required magic number rather than use heuristics.
Java classclass fileclass files
The history of this magic number was explained by James Gosling referring to a restaurant in Palo Alto:
In Unix, Linux and other Unix-like operating systems, the first two bytes in a file can be the characters "#!", which constitute a magic number (hexadecimal 23 and 21, the ASCII values of "#" and "!") often referred to as shebang, prefix the first line in a script, with the remainder of the line being a command usually limited to a max of 14 (when introduced) up to usually about 80 characters in 2016.
Detecting such constants in files is a simple and effective way of distinguishing between many file formats and can yield further run-time information.
Memory is usually viewed in hexadecimal, so memorable repeating or hexspeak values are common.
Created by programmers as memorable magic numbers, hexspeak words can serve as a clear and unique identifier with which to mark memory or data.
Magic numbers implement strongly typed data and are a form of in-band signaling to the controlling program that reads the data type(s) at program run-time.
In computer programming, an example of in-band signaling are magic numbers, used for signaling of file formats.
The shebang is actually a human-readable instance of a magic number in the executable file, the magic byte string being 0x23 0x21, the two-character encoding in ASCII of #!.
magicDeep magicblack magic
Thus, the header constant did provide an illusion and met the criteria for magic.
Kirk McKusickM. Kirk McKusickM. McKusick
The magic number used in the UFS2 super block structure reflects McKusick's birth date: #define FS_UFS2_MAGIC 0x19540119 (as found in /usr/include/ufs/ffs/fs.h on FreeBSD systems).
Executable programs are recognized using a magic number.
Such a value may also be used as a sentinel value to initialize newly allocated memory for debugging purposes.
These arbitrary values were sometimes referred to as magic numbers since there often was no explanation as to how the numbers were obtained or whether their actual values were significant.
The purpose of the constant is not immediately clear to someone viewing the code, so, like other such constants found in code, it is often called a magic number.
This would be a magic number.
sentinela variable contains no useful informationflag value
OSTypefour character codefile type codes