Unicorns

Unicorn is legendary and mythical animal with single pointed horn. It was depicted as a creature in arts and crafts of all civilizations.

Uniforns or narwhals are startup companies whose evaluation exceeds one billion dollars. Unicorns are supposed to be rare animals, however there are around two hundred. Top unicorns are uber, xioami, airbnb, palantir and snapchat. Uber is worth sixty two billion dollars now. Decacorns are companies whose evaluation exceeds ten billion dollars and they include dropbox and pinterest.

References
Unicorn
Unicorns

Next to Pearls

Reading further to Programming Pearls

1. Software Requirements and Specifications by Michael Jackson
2. Conceptual Blockbusting by James L Adams
3. How to solve it by Polya
4. Code Complete by Steve McConnell
5. Rapid Development by Steve McConnell
6. Project Survival Guide by Steven McConnell
7. Science of Programming by David Gries
8. Practice of Programming by Kernigan and Pike
9. Medical Detectives by Berton Rourche
10. Hints for Computer System Design by Butler Lampson
11. How to Lie with Statistics by Darrel Huff
12. Innumeracy : Mathematical illiteracy and it's consequences by John Allen Paulo
13. Data Structures and Algoritms by Aho Hopcroft Ullman
14. Introduction to Algorithms by Corman, Leiserson, Rivest
15. Mythical Man Month by Fred Brooks
16. The Art of Computer Programming by Donald Knuth
17. Algorithms by Robert Sedgewick
18. Mathematical theory of communication by Claude Shannon
19. Literate Programming by Donald Knuth

Ballot problem

In an election where a candidate gets p votes and other candidate gets q votes and p > q, the probability that the first candidate maintains the lead throughout the counting procedure is (p-q)/(p+q).

It was first published by W.A. Whitworth in 1878 and later rediscovered by Joseph Louis Francois Bertrand in 1887.


Sources
Bertrand's ballot theorm
Ballot problem solution

P/E ratio

P/E ratio means price of a stock of company divided by earnings per share (EPS).  It is the amount of money share holders want to pay for earning one dollar money. A good P/E ratio is between 15 to 25. Comparing P/E ratios of companies in same field is meaningful. S/W or technology companies may have higher P/E whereas old stable industries may have lower P/E value.

If it is more, it may mean either market is optimistic and thinks there is risk or there is no growth for the company or it may mean overvalued than it is worth. If it is less, then market is pessimistic about the the company or it may mean it is undervalued than it is worth in reality.

Price = Earnings * P/E ratio.
Stock price increases either because the real earnings increased or because the market perception caused the multiple (P/E) to increase.

If a company acquires other company with higher P/E, then it prefers cash purchase. If a company acquires other company with lower P/E, then it prefers to do stock purchase.

References
investopedia P/E
wikipedia P/E

PIN codes

PIN code stand for Postal Index Number code. It was introduced on independence day in 1972. It is six digits long. The first digit represents a zone and it is typically one or more states. There is one functional zone for army and military purpose. The first three digits together represent a geographical region or sorting facility at a main post office. Fourth digit represents the delivery route and zero digit means it is in main area of the post office. Fifth and sixth digits represent the delivery post office.

PIN codes start from North most states around Delhi and head south along the west coast in increasing order and then they head north along the east coast after reaching the south and head west and end in central India.

• 1 - Delhi, Haryana, Punjab, Himachal Pradesh, Jammu and Kashmir, Chandigarh
• 2 - Uttar Pradesh, Uttarakhand
• 3 - Rajasthan, Gujarat, Daman and Diu, Dadra and Nagar Haveli
• 4 - Goa, Maharashtra, Madhya Pradesh, Chhattisgar
• 5 - Andhra Pradesh, Karnataka, Telangana
• 6 - Tamil Nadu, Kerala, Puducherry, Lakshadweep
• 7 - Odisha, West Bengal, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura,Meghalaya, Andaman and Nicobar Islands, Assam, Sikkim
• 8 - Bihar, Jharkhand
• 9 - Army Post office (APO) and Field Post office (FPO)

References
wikipedia PIN codes

zip codes

ZIP stands for zone improvement plan. There are 41,716 codes in United States of America.

Robert A. Moon, a postal employee, noted that rail based and address based delivery systems would not scale and fought for twenty years for number based systems what was to become the ZIP code with three digits. He divided the country into 900 regions.  H. Bently Hahn added fourth and fifth digits and persuaded the panel to go with five digits and credited with new system that revolutionized the postal delivery. It is further extended to nine digits or zip+four system in 1983.

Before zip codes were invented, workers sorted mail in some special mail cars in trains. United states post office (USPS) lost lot of trained personal during wars. Volume of mail was increasing rapidly - 43 million mails every week or 30 billion mails annually. Planes started carrying more mail than trains did.

The numerical system made easy transition to mechanized processing from manual sorting. However it took long time for people to start writing zip code along with mail address. United states post office (USPS) came up with cartoon character Mr. ZIP and campaigned that including zip code makes mailman travel with high speed. Mr. ZIP character was originally designed by Howard Wilcox of Cunnigham and Walsh Ad Agency for use by a Newyork bank to use in banking by mailing campaign. AT&T purchased the design and gave to USPS without the cost.

Some ZIP codes are unique to single high volume address like 20500 for white house and 72716 for Walmart headquarters. They are 2122 such codes. Some ZIP codes are for military, diplomat offices and embassies. There are 532 such codes. Some ZIP codes are used for solely post box addresses in some cities. There are 5122 such codes. Rest of the ZIP codes are based on geographical location. They are 29773 such codes.  Wealthiest zip code is 90210 for Beverly Hills, CA.

First digit denotes a state or group of states. The digit 9 is shared by west coast states California, Oregon and Washington, Alaska, Hawai and several other islands. Second and third digits denote a region or large city in those states. Together the first three digits denote sectional facility center or the main sorting and distribution center for an area. Fourth and Fifth digits denote group of addresses within a region. ZIP codes can cross state and other political boundaries. ZIP codes start on east coast and increase southwards and continue heading towards northward and westward east of Mississippi river, southward west of Mississippi river and northward on west coast.

ZIP codes are also used for gathering statistics like cenus data, marketing campaigns to identify purchase patterns, income patterns and demographics and as key in several online database systems.

References:
ZIP code
Robert Moon
H. Bently Hahn
wikipedia Mr. ZIP
USPS Mr. ZIP
Zip code statistics

Abraham Lincoln

Abraham Lincoln is one of the greatest american presidents. He led the nation through the civil war and kept the union with all possible ways he can - with diplomacy, with war and with power.

He changed parties but he campaigned and fought for abolition of slavery all the time; Whigs 1834-1854, Republican 1854-1864 and National Union 1864-1865.

He is still remembered for the following two milestone events.

• Emancipation Proclamation in 1863, an executive order by president to change the federal legal status of slaves in southern states to free.
• Thirteenth amendment that completed abolishing slavery in all states except as punishment for a crime. Senate passed april 18th, 1864 and house passed it after one unsuccessful vote on jan 31st, 1865.

Similar ammendments were attempted by Arthur Livermore in 1818 and John Quincy Adams in 1839.

References
Abraham Lincoln
Thirteenth Ammendment