Turkish nations for long centuries heve preferred to use Crescent, star and red background on nation flags, military banners etc...
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Here is the information I've collected shortly:
Source 1 :
Turkey
Source 2 :
Flag of Turkey - Wikipedia, the free encyclopedia
Source 3 :
Ottoman flag - Wikipedia, the free encyclopedia
Source 4 :
National flags inspired by the flag of Turkey - Wikipedia, the free encyclopedia Turkey
Türkiye - Republic of Turkey, Türkiye Cumhuriyeti 
National flag of Turkey - ( Source 1)
Flag in use since 1844 and officially adopted 5 June 1936,
coat of arms adopted in 1927.
Proportion: 2:3.
Description: Red flag with a white crescent and star.
Use: on land as the national, civil and war flag,
on sea as the national, civil and war ensign and the naval jack.
Colour approximate specifications (as given in
Album des Pavillons [pay00]):
- Red: Pantone 186 c / CMYK (%) C 0 - M9 0 - Y 80 - K 5
Risk of confusion with: Tunisia.
Meaning of the Turkish flag Source 1
Meaning of flags is a difficult topic, especially when flags are very ancient. There is usually sparse historical evidence and a lot of legends. Moreover, individuals may have their own interpretation of their national flag. Concerning Turkey, I found the following in the authoritative books of W. Smith (
[smi75c] &
[smi80]):
Historical facts:Red has been prominent in Turkish flags for 700 years. The star and crescent are Muslim symbols, but also have a long pre-Islamic past in Asia Minor. The basic form of the national flag was apparently established in 1793 under Sultan Selim III, when the green flags used by the navy were changed to red and a white crescent and multipointed star were added. The five-pointed star dates from approximately 1844. Except for the issuance of design specifications, no change was made when the Ottoman Empire became the Republic of Turkey and the Caliphate (religious authority) was terminated. Many traditions explain the star and crescent symbol. It is known that Diana was the patron goddess of Byzantium and that her symbol was a moon. In 330, the Emperor Constantine rededicated the city - which he called Constantinople - to the Virgin Mary, whose star symbol was superimposed over the crescent. In 1453 Constantinople was captured by the Ottoman Turks and renamed Istanbul, but its new rulers may have adopted the existing emblem for their own use.
Legends:A reflection of the moon occulting a star, appearing in pools of blood after the battle of Kosovo in 1448*, led to the adoption of the Turkish flag by Sultan Murad II according to one legend. Others refer to a dream of the first Ottoman Emperor in which a crescent and star appeared from his chest and expanded, presaging the dynasty's seizure of Constantinople. At least three other legends explain the flag.
Ivan Sache, 20 January 1999
*There was a "Second Kosovo War", which is as popular as the first one from the perspective of Ottoman history, and the year 1448 refers to this war. This war continued for only two days (17-19 October 1448) and it was in the time of Sultan Murat II, unlike the first war (which was during the rule of Sultan Murat I). The resources refer the second war as a bloody war, which supports the legend of the origin of Turkish flag.
Onur Özgün, 2 April 2005
Nicknames of the flag
Turkish people call their national flag
ay yildiz (moon star).
Resat Erel, 20 June 1999
Ayyildiz is also the name of a Turkish city at approx. 36.80 latitude, 37.73 longitude.
Don White, 2 August 2004
Another nickname for the flag is
al sancak, which translates into "red banner". Besides,
sancak has its unique meaning in Turkish and cannot be directly translated into English, but the nearest to that is the "banner".
Cem Kenan Magripli, 28 January 2004
I think "red banner" is a good translation for
al sancak. I think this nickname for the Turkish flag comes from the words of the Turkish national anthem
Istiklal Marsi. The poet of national anthem, Mehmet Akif Ersoy, used this metaphor for the flag.
Coming to the translation,
sancak is defined as "banner", "flag" or "standard" in Turkish-English dictionaries that I've looked up. The Turkish definition of
sancak is "flag carried by military unit, usually having writings, fringe and pole". Today, I think it corresponds to "banner", however its meaning when it was first used could be different and can mean any flag.
The very same word was used in
Ottoman times for an administrative unit (see also
Sandžak in Serbia and Montenegro). but is does not correspond to any administrative division in Turkey any more.
Onur Özgün, 28 January 2004
As I understood, the administrative unit was named
sancak after it being ruled by a ruler who had right and duty to maintain a military unit that carried his flag, that is a (territoirial)
sancak would provide one unit with a flag.
Željko Heimer, 29 July 2004
Construction sheet for the Turkish flag 
Construction sheet for the flag of Turkey -
The construction sheet is given in a book on Turkish flags
[kur92].
The book is in Turkish, 170 pages, with some 30 colour plates of historical and current flags and some black and white photos. It might be that the construction is taken from the
flag Law which is quoted in full in the book.
The above image is based on the construction sheet in the book, adapted slightly to make it better looking as a digital image. The base unit is the flag width and other dimensions are expressed through it. The center of the circle forming the crescent is half flag width from the hoist, with diameter of the same (i.e. radius 1/4 as indicated on the image). The inner circle forming the crescent has a radius of 1/5 and is offset towards the fly 0.0625 (1/16) [the book actually give number 0.625 here, but that must be printing error as it would make no sense!]. The two circles intersect, forming the "indentation" of the crescent to be 1/3. The five-pointed star is inscribed in a circle with diameter 1/4, tangential to the line connecting the intersections of the two circles. The construction sheet also gives the width of the white heading on hoist (not shown on the image) as 1/30 of the flag width.
Željko Heimer, 2 March 1999
In a book on Turkish flags
[vht94] issued by the VDCN (March 1994) is the same construction sheet. In the accompanying table, the white heading on hoist is given as "Width of the seam band".
Mark Sensen, 8 March 1999
The very same construction sheet already appeared in the
Flaggenbuch (1939-1941)
[neu92] Ivan Sache, 1 October 1999
OR (source 2)
Legal Basis
The fundamentals of the Turkish flag were laid down by the
Turkish Flag Law (Law No. 2994) on May 29, 1936. The
Turkish Flag Regulation Law (Law No. 2/7175) dated July 28, 1937, and the
Supplementary Regulation (Law No. 11604/2) dated July 29, 1939, were enacted to describe how the definite geometric proportions of the flag should be established. The
Turkish Flag Law (Law No. 2893) dated September 22, 1983, and published in the Official Gazette on September 24, 1983, was promulgated six months after its publication. According to
Article 9 of Law No. 2893, a statute including the fundamentals of the implementation was also published.
(source 2)
Turkish national anthem
The Turkish national anthem, the Independence March (
İstiklâl Marşı) was adopted on 12 March 1921. Following a competition and the submission of 724 proposals, the Grand National Assembly unanimuously adopted the Independence March written by Mehmet Akif Ersoy (1863-1936). Until 1930, the anthem was performed with the music written by Ali Rşfat Çağatay in 1924. Since then, the anthem is performed with the music written by Osman Zeki Üngör, and only the two first stanzas (which mentions the flag), out of ten, are sung.
Korkma, sönmez bu şafaklarda yüzen al sancak;
Sönmeden yurdumun üstünde tüten en son ocak.
O benim milletimin yıldızıdır parlayacak;
O benimdir, o benim milletimindir ancak.
Çatma, kurban olayım çehreni ey nazlı hilal!
Kahraman ırkıma bir gül! ne bu şiddet bu celal?
Sana olmaz dökülen kanlarımız sonra helal,
Hakkıdır, Hakk'a tapan, milletimin istiklal!
Never fear! For the crimson flag that proudly waves in these dawns, shall never fade,
Before the last fiery hearth that is ablaze within my nation burns out.
For it is the star of my nation, and it will forever shine;
It is mine; and solely belongs to my valiant nation.
Frown not, I beseech you, oh thou coy crescent,
But smile upon my heroic race! Why the anger, why the rage?*
Our blood which we shed for you will not be worthy otherwise;
For freedom is the absolute right of my God-worshipping nation
*There is a literary element being employed here that may not be immediately noticeable. The Turkish flag is comprised of a white crescent and star superimposed on a crimson background. The poet is creating an imagery of a crescent and comparing it to the frowning eyebrows of a sulky face. To be specific, the flag (under threat from invading nations against whom victory seems initially impossibly difficult to achieve, hence "coy") is being treated as a coy maiden with a sulky face (resentment of the invasion) who is playing hard-to-get.
Source: Wikipedia Ivan Sache, 27 September 2006 (source 1)
----------------------
The smallest flag of the World (700 nanometers wide and about 2 nanometers high), produced at the
Bilkent University Nanophysics Department. (source 2)
----------------------
Ottoman flag 
(source 3)
The term
Ottoman flag refers to any of the flags used by the ruling Sultans of the
Ottoman Dynasty. Various flags were used within the
Ottoman Empire during its existence, and the sultan also used different personal flags on different occasions of state. Due to the complex social and political organization of the Ottoman Empire, throughout most of its history there was no single proper
national flag, until 1844. In 1844 the current
Turkish flag, which derived from the
Ottoman Navy flag of 1793-1844, was adopted as the first official Ottoman national flag, as part of the
Tanzimat reforms. This flag is still used by the
Republic of Turkey. The geometric proportions of this flag were legally standardized with the Turkish Flag Law in 1936.
The use of the star-and-crescent flag associated with the late empire (with a star of five points) are well documented with photographs; there are also sources which state that the flag of the late
Ottoman Empire (and later of the
Republic of Turkey) is called
Ay Yıldız, which means
Moon Star
-----------------------------------------(source 4)
Turkic-populated entities 
Flag of Turkmenistan from
2001 
Flag of Uzbekistan from
1991 
Flag of Azerbaijan from
1990 
Flag of Northern Cyprus from
1983
Most of the other Turkic countries have adopted flag designs containing sky blue, a reference to the old
Tengri belief. It's also common to include the
tamga (insignia) of the nation.
Former possessions of Ottoman Empire 
Flag of Algeria since
1962 
Flag of Tunisia since
1831 Former countries and territories 
Flag of East Turkestan 1932-
1934,
flag also used by the East Turkestan Independence Movement, but banned by China 
Flag of the
Hatay State,
1938-
1939 
Flag of the Kingdom of Egypt 1922-
1952 
Flag of the Independence Movement in the Indonesian province of Aceh, rebelling against both Dutch colonial rule and the post-1949 Indonesian government (see Aceh War and Flag of Turkey#Similarity with the Aceh Independentist Flag)
Similarity with the Aceh Independentist Flag Aceh independentist flag
The flag used by the independence-seeking rebels in the
Indonesian province of
Aceh, who have conducted a decades-long struggle against both Dutch colonial rule and the post-
1949 Indonesian government, bears an obvious resemblance to the flag of Turkey; presumably dating from the devoutly Muslim inhabitants of 16th century Aceh who declared allegiance to the Ottoman Sultan and Caliph
Suleiman the Magnificent in 1566 and asked for his support against the encroaching Portuguese and Dutch, upon which the Ottoman Indian Ocean Fleet under
Kurtoğlu Hızır Reis arrived at Aceh in 1569.
[1] Other countries 
Flag of Comoros since
2003 
Flag of Maldives since
1965 
Flag of Mauritania since
1959 
Flag of Pakistan since
1947 
Flag of Malaysia since
1963
It should be noted that in all flags except Tunisia, Malaysia and Turkey itself there is the presence of the colour
green, which is regarded as the traditional colour of Islam (although until 15th century the
Ottoman Flag had a green background).
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