Null

Null (pronounced nuhl)

(1) Without value, effect, consequence, or significance; being or amounting to nothing; nil; lacking; nonexistent; something with a value or measure of zero; of or relating to zero.

(2) In electronics, a point of minimum signal reception, as on a radio direction finder or other electronic meter.

(3) In law, as null and void, without legal force or effect; not valid.

(4) In computing, Null (or NULL), a special marker and keyword in SQL (Structured Query Language) indicating that something has no value.

(5) In computing, the null character, the zero-valued ASCII character (also designated by NUL), often used as a terminator, separator or filler; this symbol has no visual representation; as null pointer (sometimes written NULL, nil, or None), used in computer programming for an uninitialized, undefined, empty, or meaningless value; as Null string, the unique string of length zero (in computer science and formal language theory).

(6) In computing, the null device, a special computer file (/dev/null on Unix systems) that discards all data written to it.

(7) In communications, as null modem, a specially wired serial communications cable.

(8) In mathematics, a zero value in several branches of the discipline including null set, a set that is negligible in some sense; of or relating to a set having no members or to zero magnitude; also an older term for the empty set.

(9) In physics, a point in a field where the field quantity is zero; as null vectors or curves in the causal structure of a Lorentzian manifold such as a Minkowski space-time.

(10) In statistics, as null hypothesis, a concept in hypothesis testing; companion concept is the null result, the absence of a hypothesized effect in the outcome of a scientific experiment

(11) In linguistics, as null (or zero) morpheme, a concept describing a morpheme (the smallest meaningful unit in a language (a morpheme is not identical to a word) that has no phonetic form.

(12) In genetics, as null allele, a nonfunctional allele (a variant of a gene) caused by a genetic mutation.

(13) In political history as Stunde Null (a German military planning term meaning "Hour Zero"), a term referring to midnight on 8 May 1945 in Germany marking the end of World War II in Europe and the birth a new Germany (an attempt to dissociate post-war Germany from the Nazis).  The period immediately following this time is the Nachkriegszeit (the time after the war).

(14) One of the beads in nulled work (an ornamental craft producing work resembling beads strung on a rod).

1555–1565: From the Middle French nul, from the Latin nūllus from the Proto-Italic ne-oino-los from Proto-Italic oinos (one).  Synchronically nūllus was from ne (not) + ūllus (any) and thus meaning literally "not any".  The earlier form nulla (circa 1500), from the Italian nulla, from the Latin nūlla, feminine of nūllus (no one) was ultimately from the primitive Indo-European ne, óynos & -lós.  Null is a noun, adjective & verb, nulled is a verb & adjective, nulling is a noun & verb, nullity, nullification & nullificationist are nous and nullify, nullified & nullifying are verbs; the common nouns plural are nulls and nullings.

Null Island.

Null Island is an imaginary island located at 0°N 0°E (thus “Null”, zero being one of null’s synonyms) in the South Atlantic Ocean, the point at which equator crosses the prime meridian.  It’s not clear when Null Island was first “discovered” but it delighted many when in 2011 it appeared on Natural Earth, a public domain map dataset created by volunteer cartographers and GIS (geographic information system) analysts.  A modest 1m² "land mass" (actually a buoy) located at 0°N 0°E in the digital dataset, Null Island was intended to help analysts flag errors in geocoding.  Somewhat analogous with the DNS (Domain Name System) which maintains a relationship between IP (Internet Protocol) addresses (which with computer networks communicate) and the familiar website names (which real people use), geocoding is a process which converts a physical address (such as a street address) into geographic coordinates, the most familiar of which are latitude and longitude.  It permits address to appear on digital maps and enables location-based services and applications to be integrated and distributed, mapping, navigation & advertising services depending on the system.  Of late, a particularly helpful application of the service has been the tracking of the spread of diseases. 

IBM & Null

In 1981, IBM explained why, in file systems, null had to exist in every directory (now often called folders).  If null didn’t exist, IBM maintained, operating systems wouldn’t necessarily be able to determine which were empty.  Advances in operating systems over forty-odd years, mean that’s no longer a problem but with the technology available in 1981, some of it dating back decades, the issue was real.  IBM also published what turned out to be a prescient vision of what became the widely distributed file systems of the internet, spread across continents, running on disparate hardware and operating systems yet able still functionally and administratively to interact.  Modern programming languages still take advantage of the existence (or non-existence) of null.  Below is a Python script to both check if a directory is empty and also check for exceptional situations such as a directory not existing.

import os
def main():
    dirName = '/home/varun/temp';
    '''
        Check if a Directory is empty and also check exceptional situations.
    '''   
    if os.path.exists(dirName) and os.path.isdir(dirName):
        if not os.listdir(dirName):
            print("Directory is empty")
        else:   
            print("Directory is not empty")
    else:
        print("Given Directory don't exists")
    '''
        Check if a Directory is empty : Method 1
    '''   
    if len(os.listdir('/home/varun/temp') ) == 0:
        print("Directory is empty")
    else:   
        print("Directory is not empty")
    '''
        Check if a Directory is empty : Method 2
    '''   
    if not os.listdir('/home/varun/temp') :
        print("Directory is empty")
    else:   
        print("Directory is not empty")
    print ("****************")
if __name__ == '__main__':
    main()
Output:
Directory is empty
Directory is empty
Directory is empty

In the commercial art business, if no frame is chosen, the order is tagged "Null Frame".

In computer programming, the "null frame" is a data packet containing no useful information and existing usually for the purposes of (1) maintaining an open comms channel or (2) as a marker for an end of transmission.  Null Frames are often used in conjunction with “heartbeat” (or “keepalive”) markers which provide a visual symbol indicating a connection remains active.  However, because null frames can be of variable size, they’re of use also as markers of the addressable space available in memory or buffers.  While there are other ways of doing this, null frames provide information about resource availability while themselves consuming almost no resources.  In the commercial art business, the expression “null frame” is used to indicate the customer has specified the product be supplied unframed.