The Secret Life of Programs - Jonathan Steinhart

Date: 2023-04-07
| For example, 100 different values in the range 0–99 can be
| represented by two digits.
Chapter: Representing Integers Using Bits


Date: 2023-04-06
| 15 different positive and negative numbers in total, not 16,
| because there is both a positive 0 and a negative 0
Chapter: Representing Integers Using Bits


Date: 2023-04-06
| and magnitude representation because there’s a bit that represents
| a sign and bits that represent the magnitude, or how far the value
| is from zero
Chapter: Representing Integers Using Bits


Date: 2023-04-07
| 0 .  1 0 0 (0 × 21
Chapter: Representing Real Numbers


Date: 2023-04-07
| A number that’s prefixed with 0x is a hexadecimal number—for
| example, 0x12f
Chapter: Easier Ways to Work with Binary Numbers


Date: 2023-04-07
| Over time the world has settled on 8-bit chunks as a fundamental
| unit, which we call a byte.
Chapter: Naming Groups of Bits


Date: 2023-04-07
| This led to the creation of new IEC standard prefixes: kibi (KiB)
| for 210, mebi (MiB) for 220, gibi (GiB) for 230, and tebi (TiB)
| for 240. These are slowly catching on, although “kibis” sounds
| like dog food to me.
Chapter: Naming Groups of Bits


Date: 2023-04-07
| Unicode Transformation Format–8 bit (UTF-8
Chapter: Representing Text


Date: 2023-04-07
| the stability that comes from using decision criteria is the primary
| reason we build digital (discrete) computers.
Chapter: The Case for Digital Computers


Date: 2023-04-07
| This is how modern hardware works. We take advantage of the transfer
| function’s toe and shoulder regions, called cutoff and saturation,
| respectively, in electrical engineering language. There’s
| plenty of wiggle room; getting the wrong output would take a lot
| of interference. The transfer function curve is so steep that the
| output snaps from one value to another.
Chapter: The Case for Digital Computers


Date: 2023-04-07
| when waiting for the water temperature to change in the shower after
| you’ve turned the knobs. This effect is called propagation delay
Chapter: A Short Primer on Electricity


Date: 2023-04-08
| Remember that suddenly turning off the power to a coil generates
| very high voltage for an instant and that air becomes conductive
| at high voltages. This phenomenon often results in sparks
Chapter: Building Hardware for Bits


Date: 2023-04-08
| These days transistors rule. A contraction of transfer resistor,
| a transistor is similar to a vacuum tube but uses a special type
| of material, called a semiconductor, that can change between being
| a conductor and being an insulator.
Chapter: Building Hardware for Bits


Date: 2023-04-08
| There are many different types of transistors, but the two main
| types are the bipolar junction transistor (BJT) and the field effect
| transistor (FET). The manufacturing process involves doping, which
| infuses the substrate material with nasty chemicals like arsenic
| to change its characteristics.
Chapter: Building Hardware for Bits


Date: 2023-04-08
| The metal-oxide semiconductor field effect transistor, or MOSFET,
| is a variation on the FET that’s very commonly used in modern
| computer chips because of its low power consumption. The N-channel
| and P-channel variants are often used in complementary pairs, which
| is where the term CMOS (complementary metal oxide semiconductor)
| originates.
Chapter: Building Hardware for Bits


Date: 2023-04-08
| You saw earlier that we get better noise immunity using digital
| (discrete) devices because of the decision criteria.
Chapter: Logic Gates


Date: 2023-04-08
| hysteresis, in which the decision criterion is affected by history
Chapter: Logic Gates


Date: 2023-04-08
| Alexander Graham Bell (1847–1922) invented twisted-pair cabling,
| in which pairs of wires were twisted together for the electrical
| equivalent of snuggling (see Figure 2-33). He also patented the
| telephone. Today, twisted pair is ubiquitous; you’ll find it in
| USB, SATA (disk drive), and Ethernet cables
Chapter: Logic Gates


Date: 2023-04-08
| An interesting application of differential signaling can be found
| in the Wall of Sound concert audio system used by the American band
| The Grateful Dead (1965–1995). It addressed the problem of vocal
| microphone feedback by using microphones in pairs wired so that
| the output from one microphone was subtracted from the output of
| the other. That way, any sound hitting both mics was common-mode
| and canceled out.
Chapter: Logic Gates


Date: 2023-04-11
| The schematic on the left illustrates how totem-pole outputs get
| their name. The top switch in the figure is called an active pull-up
| because it connects the output to the high logic level to get a 1
| on the output.
Chapter: Logic Gates


Date: 2023-04-11
| We can use a passive pull-up, which is just a pull-up resistor
| connecting the output to the supply voltage, which is the source
| of 1s. This is called VCC for bipolar transistors and VDD for MOS
| (metal-oxide-semiconductor) transistors.
Chapter: Logic Gates


Date: 2023-04-11
| What’s happening here is that when neither open-collector output
| is low, the resistor pulls the signal up to a 1. The resistor
| limits the current so that things don’t catch fire. The output
| is 0 when any of the open-collector outputs is low. You can wire
| a large number of things together this way, eliminating the need
| for an AND gate with lots of inputs.
Chapter: Logic Gates


Date: 2023-04-11
| small-scale integration (SSI) part, so that one package could
| replace 40
Chapter: Building More Complicated Circuits


Date: 2023-04-12
| Combinatorial logic deals only with the present state of
| inputs. Sequential logic, however, deals with both the present and
| the past.
Chapter: 3 SEQUENTIAL LOGIC


Date: 2023-04-12
| piezoelectric effect
Chapter: Representing Time


Date: 2023-04-12
| Sound vibrations generated by applying electricity to crystals are
| responsible for the annoying beeps made by many appliances. You
| can spot a crystal in a circuit diagram by the symbol shown
Chapter: Representing Time


Date: 2023-04-12
| Oscillators supply clocks to computers. A computer’s clock is
| like the drummer in a marching band; it sets the pace for the
| circuitry. The maximum clock speed or fastest tempo is determined
| by the propagation delays.
Chapter: Representing Time


Date: 2023-04-12
| The fastest parts that fetch the highest price go into one bin;
| slower, less expensive parts go into another; and so on. It’s not
| practical to have an infinite number of bins, so there’s variance
| within the parts in a bin, although it’s less than the variance
| for the whole lot of parts.
Chapter: Representing Time


Date: 2023-04-12
| This is one reason why propagation delays are specified as a range;
| manufacturers provide minimum and maximum values in addition to a
| typical value. A common logic circuit design error is to use the
| typical values instead of the minimums and maximums.
Chapter: Representing Time


Date: 2023-04-12
| When you hear about people overclocking their computers, it means
| they’re gambling that their part was statistically in the middle of
| its bin and that its clock can be increased by some amount without
| causing the part to fail
Chapter: Representing Time


Date: 2023-04-16
| Core memory is an antique nonvolatile
Chapter: Memory Organization and Addressing


Date: 2023-04-16
| ROM can be written once and then read multiple times.
Chapter: Memory Organization and Addressing


Date: 2023-04-16
| core rope memory
Chapter: Memory Organization and Addressing


Date: 2023-04-16
| Along came programmable read-only memory (PROM), ROM chips that you
| could program yourself, but only once. The original mechanism for
| PROM involved melting nichrome (a nickel-chromium alloy) fuses on
| the chip. Nichrome is the same stuff that makes the glowing wires
| in your toaster.
Chapter: Memory Organization and Addressing


Date: 2023-04-16
| erasable programmable read-only memory (what a mouthful!), or
| EEPROM. This is an EPROM chip that can be erased electrically—no
| light, no quartz window. Erasing EEPROM is comparatively very slow,
| though, so it’s not something you want to do a lot. EEPROMs
| are technically RAM, since it’s possible to read and write the
| contents in any order. But because they’re slow to write and more
| expensive than RAM, they’re used as a substitute for ROMs
Chapter: Memory Organization and Addressing


Date: 2023-04-16
| Modern disks spin at 7,200 rotations per minute (RPM), which means
| a rotation takes slightly longer than 8 milliseconds.
Chapter: Block Devices


Date: 2023-04-16
| The big problem with disk drives is that they’re mechanical and
| wear out. Bearing wear is one of the big causes of disk failure.
Chapter: Block Devices


Date: 2023-04-16
| They’re slow because of the time it takes for the bits you want
| to show up under the head, but because the data is being brought
| to the head, no space is required for address and data connections,
| unlike, for example, in a DRAM.
Chapter: Block Devices


Date: 2023-04-30
| Byte 0 goes into the rightmost seat in little-endian machines like
| Intel processors. Byte 0 goes into the leftmost seat in big-endian
| machines like Motorola processors. Figure 4-4 compares the two
| arrangements.
Chapter: Memory


Date: 2023-04-30
| nuxi syndrome was coined to refer to byte-ordering problems
Chapter: Memory


Date: 2023-04-06
| These languages instead implement garbage collection, a technique
| invented in 1959 by American computer and cognitive scientist John
| McCarthy (1927–2011) for the LISP programming language. Garbage
| collection has experienced a renaissance, partly as a proscriptive
| remedy for bad pointer use.
Chapter: Garbage Collection