The Logic Gates

Logic gates are the basic components in digital electronics. They are used to create digital circuits and even complex integrated circuits. Logic gates process signals which represent true or false. Normally the positive supply voltage +Vs represents true and 0V represents false. Gates are identified by their function: NOT, AND, NAND, OR, NOR, EX-OR and EX-NOR.

AND Gate

The AND gate is an electronic circuit that gives a high output (1) only if all its inputs are high. A dot (.) is used to show the AND operation i.e. A.B. Bear in mind that this dot is sometimes omitted i.e. AB

OR Gate

The OR gate is an electronic circuit that gives a high output (1) if one or more of its inputs are high. A plus (+) is used to show the OR operation.

NOT gate

The NOT gate is an electronic circuit that produces an inverted version of the input at its output. It is also known as an inverter. If the input variable is A, the inverted output is known as NOT A. This is also shown as A', or A with a bar over the top, as shown at the outputs. The diagrams below show two ways that the NAND logic gate can be configured to produce a NOT gate. It can also be done using NOR logic gates in the same way.

NAND gate

This is a NOT-AND gate which is equal to an AND gate followed by a NOT gate. The outputs of all NAND gates are high if any of the inputs are low. The symbol is an AND gate with a small circle on the output. The small circle represents inversion.

NOR gate

This is a NOT-OR gate which is equal to an OR gate followed by a NOT gate. The outputs of all NOR gates are low if any of the inputs are high.

The symbol is an OR gate with a small circle on the output. The small circle represents inversion.

EXOR gate

The 'Exclusive-OR' gate is a circuit which will give a high output if either, but not both, of its two inputs are high. An encircled plus sign () is used to show the EOR operation.

EXNOR gate

The 'Exclusive-NOR' gate circuit does the opposite to the EOR gate. It will give a low output if either, but not both, of its two inputs are high. The symbol is an EXOR gate with a small circle on the output. The small circle represents inversion.

The NAND and NOR gates are called universal functions since with either one the AND and OR functions and NOT can be generated.

Note:

A function in sum of products form can be implemented using NAND gates by replacing all AND and OR gates by NAND gates.

A function in product of sums form can be implemented using NOR gates by replacing all AND and OR gates by NOR gates.

Logic gate symbols

Logic gates representation using the Truth table:

Summary for all 2-input gates
Inputs		Output of each gate
A	B	AND	NAND	OR	NOR	EX-OR	EX-NOR
0	0	0	1	0	1	0	1
0	1	0	1	1	0	1	0
1	0	0	1	1	0	1	0
1	1	1	0	1	0	0	1

Summary for all 3-input gates
Inputs			Output of each gate
A	B	C	AND	NAND	OR	NOR
0	0	0	0	1	0	1
0	0	1	0	1	1	0
0	1	0	0	1	1	0
0	1	1	0	1	1	0
1	0	0	0	1	1	0
1	0	1	0	1	1	0
1	1	0	0	1	1	0
1	1	1	1	0	1	0

[Source]

Preamble of the 1987 Constitution

We, the sovereign Filipino people, imploring the aid of Almighty God, in order to build a just and humane society and establish a Government that shall embody our ideals and aspirations, promote the common good, conserve and develop our patrimony and secure to ourselves and our posterity the blessings of independence and democracy under the rule of law and a regime of truth, justice, freedom, love, equality, and peace, do ordain and promulgate this Constitution.

Biography of Jose Rizal

JOSE RIZAL (full name: José Protasio Rizal Mercado y Alonso Realonda) , the national hero of the Philippines and pride of the Malayan race, was born on June 19, 1861, in the town of Calamba, Laguna. He was the seventh child in a family of 11 children (2 boys and 9 girls). Both his parents were educated and belonged to distinguished families. His father, Francisco Mercado Rizal, an industrious farmer whom Rizal called "a model of fathers," came from Biñan, Laguna; while his mother, Teodora Alonzo y Quintos, a highly cultured and accomplished woman whom Rizal called "loving and prudent mother," was born in Meisic, Sta. Cruz, Manila.

At the age of 3, he learned the alphabet from his mother; at 5, while learning to read and write, he already showed inclinations to be an artist. He astounded his family and relatives by his pencil drawings and sketches and by his moldings of clay. At the age 8, he wrote a Tagalog poem, "Sa Aking Mga Kabata," the theme of which revolves on the love of one’s language.

In 1877, at the age of 16, he obtained his Bachelor of Arts degree with an average of "excellent" from the Ateneo Municipal de Manila. In the same year, he enrolled in Philosophy and Letters at the University of Santo Tomas, while at the same time took courses leading to the degree of surveyor and expert assessor at the Ateneo. He finished the latter course on March 21, 1877 and passed the Surveyor’s examination on May 21, 1878; but because of his age, 17, he was not granted license to practice the profession until December 30, 1881. In 1878, he enrolled in medicine at the University of Santo Tomas but had to stop in his studies when he felt that the Filipino students were being discriminated upon by their Dominican tutors.

On May 3, 1882, he sailed for Spain where he continued his studies at the Universidad Central de Madrid. On June 21, 1884, at the age of 23, he was conferred the degree of Licentiate in Medicine and on June 19,1885, at the age of 24, he finished his course in Philosophy and Letters with a grade of "excellent." Having traveled extensively in Europe, America and Asia, he mastered 22 languages. These include Arabic, Catalan, Chinese, English, French, German, Greek, Hebrew, Italian, Japanese, Latin, Malayan, Portuguese, Russian, Sanskrit, Spanish, Tagalog, and other native dialects. A versatile genius, he was an architect, artists, businessman, cartoonists, educator, economist, ethnologist, scientific farmer, historian, inventor, journalist, linguist, musician, mythologist, nationalist, naturalist, novelist, ophthalmic surgeon, poet, propagandist, psychologist, scientist, sculptor, sociologist, and theologian. He was an expert swordsman and a good shot.

In the hope of securing political and social reforms for his country and at the same time educate his countrymen, Rizal, the greatest apostle of Filipino nationalism, published, while in Europe, several works with highly nationalistic and revolutionary tendencies. In March 1887, his daring book, NOLI ME TANGERE, a satirical novel exposing the arrogance and despotism of the Spanish clergy, was published in Berlin; in 1890 he reprinted in Paris, Morga’s SUCCESSOS DE LAS ISLAS FILIPINAS with his annotations to prove that the Filipinos had a civilization worthy to be proud of even long before the Spaniards set foot on Philippine soil; on September 18, 1991, EL FILIBUSTERISMO, his second novel and a sequel to the NOLI and more revolutionary and tragic than the latter, was printed in Ghent.

Because of his fearless exposures of the injustices committed by the civil and clerical officials, Rizal provoked the animosity of those in power. This led himself, his relatives and countrymen into trouble with the Spanish officials of the country. As a consequence, he and those who had contacts with him, were shadowed; the authorities were not only finding faults but even fabricating charges to pin him down. Thus, he was imprisoned in Fort Santiago from July 6, 1892 to July 15, 1892 on a charge that anti-friar pamphlets were found in the luggage of his sister Lucia who arrive with him from Hong Kong. While a political exile in Dapitan, he engaged in agriculture, fishing and business; he maintained and operated a hospital; he conducted classes- taught his pupils the English and Spanish languages, the arts. The sciences, vocational courses including agriculture, surveying, sculpturing, and painting, as well as the art of self defense; he did some researches and collected specimens; he entered into correspondence with renowned men of letters and sciences abroad; and with the help of his pupils, he contracted water dam and a relief map of Mindanao- both considered remarkable engineering feats.

His sincerity and friendliness won for him the trust and confidence of even those assigned to guard him; his good manners and warm personality were found irresistible by women of all races with whom he had personal contacts; his intelligence and humility gained for him the respect and admiration of prominent men of other nations; while his undaunted courage and determination to uplift the welfare of his people were feared by his enemies. When the Philippine Revolution started on August 26, 1896, his enemies lost no time in pressing him down. They were able to enlist witnesses that linked him with the revolt and these were never allowed to be confronted by him. Thus, from November 3, 1986, to the date of his execution, he was again committed to Fort Santiago. In his prison cell, he wrote an untitled poem, now known as "Ultimo Adios" which is considered a masterpiece and a living document expressing not only the hero’s great love of country but also that of all Filipinos. After a mock trial, he was convicted of rebellion, sedition and of forming illegal association. In the cold morning of December 30, 1896, Rizal, a man whose 35 years of life had been packed with varied activities which proved that the Filipino has capacity to equal if not excel even those who treat him as a slave, was shot at Bagumbayan Field.

[Source]