What is Digital Information?

Analog vs. Digital Continuous vs. discrete E.g. real numbers vs. integers Analog quantity Digital quantity quantity quantity An analog quantity can change continuously through a range of values. The quantity passes through all the real numbers between one value and another, making no jumps. A digital quantity has only jumps, taking on discrete values like 0, 1, 2, 3, without going through the numbers in between. time time

Converting analog to digital Sound as an example Sample the waveform Each sample has discrete values Here, the values were chosen by rounding toward zero.

Digital vs. analog: Digital has… Limited precision Limited size Error-free duplication Error-free transmission The green is an analog signal. The digital representation records a value for each black dot. There are advantages and disadvantages to using digital representations of information. The signal has been "clipped" because the analog signal is outside the minimum and maximum values that can recorded. Y2k and other rollover phenomena (e.g., the date in *nix operating systems in 2038 or the number of views of the Gangnam Style YouTube video) as well as cybersecurity attacks known as "buffer overruns" or "stack overflows" are each about the fact that a value can't get any bigger. Digital music can be duplicated exactly; a copy of a copy of a copy is just as good as the original. With error checking algorithms, people and programs can exchange messages and be confident that a repeat of a repeat of a repeat is still correct.

What is binary? Can represent anything digital Presentation Name Course Name Unit # – Lesson #.# – Lesson Name What is binary? Can represent anything digital Base 2. Only two digits 0 and 1 Why is 1011 eleven? Example digits:   1 Place values 2n: x 8 4 2 Value + + +

What is binary in electronics? "High" and "low" voltage

What are computers, physically? Semiconductors N and P doped  diode, transistor Transistors make logic gates Integrated circuits include processing as well as volatile and flash memory We use semiconductors for storing and computing with those zeros and ones. The transistor

Semiconductors

Doping makes diodes and transistors Presentation Name Course Name Unit # – Lesson #.# – Lesson Name Doping makes diodes and transistors The most commonly used semiconductor material is silicon. A lot of the earth's crust is made of silicon; sand is SiO_2. Impurities can be added to a semiconductor to make an n-doped or p-doped semiconductor. Adding an atom of a group V element adds one more electron than the crystal has space for. Adding a group III element's atom creates a "hole" because the atom doesn't use one of the crystals spaces for an electron.

Transistors The first transistor was patented in 1925, although the first working point-contact transistor was not produced until 1947. Their work on that transistor earned Shockley, Bardeen, and Brattain the Nobel prize in physics in 1956.

Logic Gates AND OR NOT NAND Programs use logical statements like AND, OR, and NOT in high level programs. Pieces of hardware called logic gates can perform the same functionality at a hardware level and can be constructed from transistors and resistors. To give you a feel for how these gates can combine to make larger circuits, and even entire microchips, you will construct NAND gates using electrical components. Each type of logic gate has a special symbol for use in drawing up circuit diagrams. In order to understand circuit diagrams, you will need to know these symbols. The three basic symbols are those for NOT, AND, and OR shown on this slide. In order to create a symbol for a gate with an N (meaning NOT) at the beginning, you add a circle in front of the output line like the one in the NOT symbol. An exclusive can be appended to OR based gates when the symbol has a line intersecting both of the input lines at the base of the gate. In this case an X precedes the gate name. XOR is what you commonly think of when you mean “one or the other but not both.”

CMOS and TTL CMOS used in Very Large Scale Integrated (VLSI) circuits like the AT Mega. TTL is still used in some applications. More waste heat is generated. Modern computers use complementary metal-oxide-semiconductors (CMOS) as the basic electrical building block for microcontrollers like the AT Mega found on the Arduino, for RAM, and digital logic circuits. A CMOS device is itself built from transistors. Without the transistor the history of computing would look very different. The circuits you create in this activity will use transistor-transistor logic (TTL), meaning they are built from just transistors and resistors.  These will contain multiple logic gates and many transistors. The ATmega48PA/88PA/168PA/328P is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture.

Integrated Circuits VLSI Billions of transistors, small as a dime Used in virtually all electronics VLSI The Xbox One contains 5 billion transistors in its CPU. VLSI is a subcategory of integrated circuit standing for Very Large Scale Integration. How the most compact chips are made Closer components means faster speeds

The Future In order for computers to continue to observe Moore’s Law, non-traditional options are investigated Optoelectronics Nanotechnology Quantum Computing The term microcomputer is applied to regular desktop computers, as they were much smaller than mainframes. The Arduino UNO is considered a nanocomputer due to its size and power.