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Episode 20 -- June 27th, 2016 -- The very beginnings of Digital Electronics, Gates, Memory, CPU Instructions, Firmware and Software.
Listen to the episode 52.8 MB MP3
Static vs Current Electricity
Ohm's Law: E = IR Voltage ("Electro-motive Force") in volts is equal to the Current ("Inductance") in Amperes or Amps multiplied by the Resistance in Ohms.
Alternating vs Direct Current
Diodes and Transistors
Bias a transistors to make an amplifier or a switch
Digital Logic Runs on a clock pulse. Think of a clock as a metronome which, every time it swings and makes a "Tock" at that moment - all the gates activate and do their thing, whatever that thing is.
Standard Logic Gates
A Flip-Flop is a memory circuit which can hold a single bit of data.
A row of 8 flip-flops in a row compose a single "Byte"e.
1 bit has 2 values; 2 bits has 4 values; 3 bits has 8 values; 4 bits can hold one of 16 values; 8 bits together (1 byte) can hold one of 256 different values.
ASCII (American Standard Code for Interchanging Information) is a correspondance between a single byte and one of 128 (7-bits) different symbols, letters (upper and lower case), numerals, and control characters.
Unicode has 16 or 32 bits to choose characters from almost all the different alphabets of almost every language in the world.
Big-Endian vs Little-Endian
shifting bits left divides by two, shifting right multiplies by two.
A central processing unit (CPU) is the heart of a computer. It is digital circuit which -in order to function- requires a bunch of Random Access Memory and a few registers and a clock signal. The registers are always built into the CPU and soetimes, some RAM and occasionally even the clock is all built-in. But mostly not.
Every time the clock pulses, such as once every million times per second for a really slow computer or once every billion times per second for an average computer, it reads the contents of the Program Counter register and goes to the memory location specified thereby and tries to interept what it finds there as an instruction to do something. Then, it does it and then increases the value of the program counter to the next memory location where it expects to find the next instruction to execute, wash, rinse, repeat. Each CPU has it's own completely arbitary langauage all its own, invented by the designer of that CPU. Some of the kinds of actions a CPU can perform include:
Load a single digit number into one of this CPU's "registers"
Load a full sized number taken from the next 1, 2, 4 or 8 bytes of data following this instruction into either a register or to a memory location pointed to by the contents of a specified register.
Move the contents of the memory location specified by the contents of the memory location referenced by the memory location located in register 3 to the memory whose location is specified by the contents of register 4 and add it to the value stored in register 5.
Add, subtract, multiply or divide the two numbers stored at the memory locations specified in registers 1 and 2 and put the result into the memory location specified by register 3.
Counting in Binary
Assembly Language vs Machine Language
Executing Random Data as Instructions and the "Hang" or "Crash".
Often, CPU's access external devices such as a mouse, hard disk drive, keyboards n'stuff, there are instructions for either communicating with specific other devices, (many of which might also be computers themselves) or some other devices are communicated by reading and writing specific blocks of memory.
Higher level langauges
Compiling and Linking
Firmware and Software
What is an operating system?
When you turn on a computer, it usually is designed to run a program to allow it find a bigger program to run. That bigger program is the Operating System, the program you use to run other programs.
Computers are in many different devices.
Modem Firmware changes
Why are Macintoshes better than Windows PC's?
Romainian hackers break into Windows computers to support their village
Light Emitting Diodes and Seven Segment Displays.
Cathode Ray Tubes with magnetic or plate deflection
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