Computer Programming

Yes. I can write a python program that asks for your name and then prints "Hi, name, good to meet you." by writing the following program.

#!/usr/bin/python

name = input("What is your name? ")

print("Hi", name + "," , "good to meet you.")

If I change the third line to

print("Hi", name + ",", "good to meet you. Your name is", len(name), "letters long.")

It will say "Hi name, good to meet you. Your name is xletters long.", thus making it a different program.

In personal computers, a motherboard is the central printed circuit board (PCB) in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple computers, the logic board.[1] It is also sometimes casually shortened to mobo.

Prior to the advent of the microprocessor, a computer was usually built in a card-cage case or mainframe with components connected by a backplane consisting of a set of slots themselves connected with wires; in very old designs the wires were discrete connections between card connector pins, but printed circuit boards soon became the standard practice. The Central Processing Unit, memory and peripherals were housed on individual printed circuit boards which plugged into the backplate. During the late 1980s and 1990s, it became economical to move an increasing number of peripheral functions onto the motherboard (see below). In the late 1980s, motherboards began to include single ICs (called Super I/O chips) capable of supporting a set of low-speed peripherals: keyboard, mouse, floppy disk drive, serial ports, and parallel ports. As of the late 1990s, many personal computer motherboards supported a full range of audio, video, storage, and networking functions without the need for any expansion cards at all; higher-end systems for 3D gaming and computer graphics typically retained only the graphics card as a separate component.

The early pioneers of motherboard manufacturing were Micronics, Mylex, AMI, DTK, Hauppauge, Orchid Technology, Elitegroup, DFI, and a number of Taiwan-based manufacturers.

The most popular computers such as the Apple II and IBM PC had published schematic diagrams and other documentation which permitted rapid reverse-engineering and third-party replacement motherboards. Usually intended for building new computers compatible with the exemplars, many motherboards offered additional performance or other features and were used to upgrade the manufacturer's original equipment

The term mainboard is applied to devices with a single board and no additional expansions or capability. In modern terms this would include embedded systems and controlling boards in televisions, washing machines, etc. A motherboard specifically refers to a printed circuit board with expansion capability typical motherboard of 2009 will have a different number of connections depending on its standard.

A standard ATX motherboard will typically have one PCI-E 16x connection for a graphics card, two conventional PCI slots for various expansion cards, and one PCI-E 1x (which will eventually supersede PCI). A standard EATX motherboard will have one PCI-E 16x connection for a graphics card, and a varying number of PCI and PCI-E 1x slots. It can sometimes also have a PCI-E 4x slot. (This varies between brands and models.)

Some motherboards have two PCI-E 16x slots, to allow more than 2 monitors without special hardware, or use a special graphics technology called SLI (for Nvidia) and Crossfire (for ATI). These allow 2 graphics cards to be linked together, to allow better performance in intensive graphical computing tasks, such as gaming and video editing.

As of 2007, virtually all motherboards come with at least four USB ports on the rear, with at least 2 connections on the board internally for wiring additional front ports that may be built into the computer's case. Ethernet is also included. This is a standard networking cable for connecting the computer to a network or a modem. A sound chip is always included on the motherboard, to allow sound output without the need for any extra components. This allows computers to be far more multimedia-based than before. Some motherboards contain video outputs on the back panel for integrated graphics solutions (either embedded in the motherboard, or combined with the microprocessor, such as the Intel HD Graphics). A separate card may still be used.

This is an historical question/answer.

In the old days, mainframe computers (like the ENIAC) used telephone relays as computational elements, relays are electronic-magnetic switches: a magnet can be turned on by driving a current through the primary side of the relay, this magnet pulls a little switch on the secondary side of the relay from one position to another. Defining the relaxed position as zero and the attracted position as one, two values are represented.

By combining multiple relays to form a larger value is an easy trick, it's like writing numbers using multiple digits:

in decimal (ten-valued numbering) the number ten is represented by one ten-valued digit and zero one-valued digits:

1 * ten + 0 * one = 10 = ten

This very same trick is used in binary (two-valued numbering) where the number two is represented by one two-valued digit and zero one-valued digits:

1 * two + 0 * one = 10 = two

As you can see the meaning of 10 differs by the numbering system, when we want to write ten in binary, we have to chain multiple digits together. First again in the decimal system:

Hundred is represented by one ten-times-ten-valued digit, zero ten-valued digits and zero one-valued digits:

1 * ten-times-ten + 0 * ten + 0 * one = 100 = hundred

Note that I wrote hundred as ten-times-ten, this is the whole idea behind numbering systems!

Writing hundred in binary, we need

one two*two*two*two*two*two-valued (sixty-four-valued) digit,

one two*two*two*two*two-valued (thirty-two-valued) digit,

zero two*two*two*two-valued (sixteen-valued) digits,

zero two*two*two-valued (eight-valued) digits,

one two*two-valued (four-valued) digits,

zero two-valued digits and

zero one-valued digits:

1 * sixty-four + 1 * thirty-two + 0 * sixteen + 0 * eight + 1 * four + 0 * two + 0 * one = 1100100 = hundred

This can be done easily with long division, but instead of checking how many times the value can be subtracted, you only have to check whether it can be subtracted (being either once or not at all):

hundred - one-hundred-twenty-eight is less than zero (0 * one-hundred-twenty-eight)

hundred - sixty-four is (equal to or) greater than zero (1 * sixty-four), remains thirty-six

thirty-six - sixty-two is (equal to or) greater than zero (1 * thirty-two), remains four

... (check for every other doubling from one)

Now you know how binary works, in a similar matter any other numbering system may be devised, some of the "more popular" are octal (eight-valued) and hexadecimal (sixteen-valued). Basically they are both ways to represent binary in a more readable way; each three binary digits may be grouped in one octal digit, each four binary digits may be grouped in one hexadecimal digit.

Now back to why we use binary. The relay is not used a low anymore, other, more compact, alternatives are currently in use.

The transistor is a small (about a match-head) device where the current flow from one point to another can be controlled by a third point, by changing the voltage on that third point. This is somewhat similar to the relay principle and is called semi-conduction; a piece of material either conducts or not depending on certain conditions (semi is a fancy name for half, so it conducts "half" the time).

Combining multiple transistors in one device (getting rid of the bulky housing of each transistor) saves a lot of space. The separate transistors are so to say integrated in a single device, hence these devices are named integrated circuits or ICs.

A computer contains a lot of these ICs, some of them housing over a million transistors. Yet they are still based on transistors, which are based on relays (or radiotubes, but let's not talk about these now), which can only be switch on or off. That's why we use binary.