23. What is a computer?#
how, physically, do we get the components we have seen?
what other components do we need?
how are those implemented
How have computers changed over time?
at the physical level
what was the context and motivation for these advances?
how does that context influence how we use computers today?
how does that influence computing as a discipline?
23.1. Let’s start with a dictionary#
we can start with a dictionary
note that this starts with reference to a person.
23.1.1. Computers as people#
and this text this particular dictionary is useful because it also includes where does the term originated like where does in that particular usage start appearing and so these are these are pretty all right this is starting 1646 1707
Use of the word computer to refer to the person still common how recently 1950s
the movie hidden figures is available on Disney+ with subscription or other streaming platforms for ~$4 streaming rental.
the book hidden figures is available at URI’s library
23.1.2. Computers as Machines#
Computers as machines started later. We started with mechanical, analog and then moved to electronic and then digital.
23.1.3. How much do we talk about computers?#
23.2. Mechanical Calculators#
how do we actually like physically make it be machine
well we’ve we’ve talked we handed out that like it’s going to reduce down to or isn’t my check and logical operations write those de back much further than
what is the mechanical calculator it works by like incrementing it doesn’t do the logic like they took not a binary representation it’s not adding via input two numbers and then it goes forward its where’s my income as you put in one number then you can add the next number and it kind of works the wheels have like the numbers on them and it uses like 9 supplement to carry over to the next bit so there’s a gear that when it hits a certain point that turns the next year and then it goes for it any Castles in the Sky why the semi did
Why did he make this?
He was 18 and his father was a tax commissioner in France and he wanted to like reduce his father’s workload
so he invented this calulator machine and received roayl privilege from France in 1649 to be only person allowed to build a manufactured Computing a calculator is like mechanical calculators
Note
Contrast this royal privelege with the 1970s where in resolving some other conflict, a court that declared the content of the computer that they cannot be found it at all and it’s free for anyone to use the concept of a computer
23.3. How did this change over time?#
calculators that are still analog so they’re still working with mechanical systems using Waze electricity becomes easier
we can start doing like electrical signal processing so we can move analog signals and start doing our agents and calculations with those are not what was really used through for transmitting information like telegram telephone all of that is analog thing
between Springs and dampers, the mechanical things are used to build these mechanical calculators and the electrical components so resistors transistors.
23.3.1. Model K Adder (1937)#
George Stibitz took some pieces at home from work at Bell Laboratory and got it working on his kitchen table.
it can do four bit addition
uses a telephone relay switch or an electromechanical switch so they’re using like a
Note
Relays are designed to repeat, or relay, a signal to the next circuit to compelte long distance telegraphs and early telphone. As the signal transpits down the cable (one circuit) it gets weaker due to loss, so it has to be repeated at some point to amplify the magnitude of it for the next length of the journey.
precursor to the complex number calculator he demonstrated how this works in combination with Telegraph for the first remote access
complex number calulator was at Bell Labs in New York City at the time in 1940 at a Confrence at Dartmouth in Hanover New Hampshire and he use a telegraph to do remote calculations on this calculator and bring them the numbers back
23.3.2. Intel 4004 (1971)#
First commercially produced microprocessor
2,250 transistors
Could perform up to 90,000 operations per second in four bit chunks
740 kHz clock speed
23.3.3. So how do these thigns actually work#
As electricity became more available, they realized that in terms of mathematical operations, electrical components resemble springs and switches
first vaccuum tubes: or diodes
diodes prevent flow of electricity in one direction and allow in the other. they can be used to create circuits that behave like the logical operations, and create the gates.
diodes only are easy for
&and|gates,transistors can operate as a switch or amplifier and can also be used to build logic gates
they’re faster, smaller, and better at more types of gates than diodes
23.4. Early Computers#
During this time small, lots of small computers were made, but each was made completely by its creators, there was no standards, per say.
These computers were also stored program computers. Meaning their operation at a program level was fixed by the circuitry.
switch the circuit to do different things between the numbers so this would get us bitwise operations of an indoor and outdoor on our numbers
23.5. von Neumann Architecture#
what else do we need besides ALU for to have like a whole computer
we eventually need clocks to time things and synchronize things to like know when to clear and when to change so that you if you want to do multiple things in sequence you can do that what else you need or want to do multiple things in sequence but don’t know what else we need a general now
In 1945 we get a draft of a general template. This is basically what we use today.
23.6. Apollo Guidance Computer (AGC)#
The AGC was the onboard computer for NASA’s Apollo programs. It provided navigation for the control capsule as well as controlled the spacecraft during moon landings. The AGC had only 72KB of fixed memory (589,824 bits). Unlike many early computers, the software for the AGC was stored in its memory and was not physically built into its hardware’s circuitry.
Additionally, this computer had RAM, which was memory that could be changed by the computer while it was running. This memory had a capacity of only 4KB (32,768 bits), which was still enough to store all the data needed to perform all calculations necessary for the missions. The AGC could be controlled by the astronauts in the command capsule by sending commands via a numeric keyboard. Its user interface consisted of a simple screen and a set of status lights that relayed information to the astronauts.
This computer is very similar to how modern computers work in the sense that it can keep data in its fixed memory even while the computer is off.
To learn more about the AGC and how it worked, you can view this article, or view the official NASA public docs on it.
23.7. Storage#
there are some thigns we have not yet seen in detail in that diagram
Ram Is Random Access we can access it whenever we want we can read and write to
ROM: is read only memory; the instructions are Permanently
In the stored program computers, the programs were in ROM.
The very earliest computers could not store any values without power.
Register: data currently processing
Memory: will be required for processing
Disk: long term storage
23.8. Questions After Class#
Note
these are last semesters. i’m behind on the new ones
23.8.1. What are the PC, MAR, MDR, etc. and what do they do#
They are various registers that each have a specific role. Learning all of these these in more detail is a good Explore badge or a single one is in more practice.
23.8.2. how does a motherboard work with all of these#
A motherboard contains all most of those components. This is also a good Deeper explroation.
23.8.3. When defining a computer, is it best to define the most current model of a computer? Or how everything functions bare bones?#
What definition dependsd on the context. If you are talking to a child who is trying to learn basic typing they need to know different things than a teenager trying to choose what type of comptuer to bring to college, which is different than the model you need to keep in mind when you’re working in a high level language, which is different than what you need when you are writing drivers.
23.8.4. How do Quantum computer logic gates differ from what we use now exactly#
Quantum computers operate on a fundamentally different object, instead of bits they have qubits. There represent, essetially some uncertainty, or randomness in the behavior, so then there are different operations needed.
23.8.5. Intel 4004 (1971) -> How it worked by Tyler Hanlon#
This was the first general purpose programmable processor which people could buy and then make or buy their own software to customize it with. This was a breakthorugh in computing as it allowed consumers to have a say in what software was used in their electronics without having to make their own. This was extremely influential advancmenet inearly comuting technologies becuase it made multiple softwares more accessible and deliverable to a wider audience. It is one of the smallest microprocessors ever made, and was develope for use in a Japanese calculator company, but was powerful enought o actually be used for a wide variety of functions.
https://spectrum.ieee.org/chip-hall-of-fame-intel-4004-microprocessor