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Thread: truly understanding history of computers

  1. #1 truly understanding history of computers 
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    I am trying to understand the history of computers in it's entirety via self-study and I am finding this extremely complicated to do. Take a look at this link:
    History of computing hardware - Wikipedia, the free encyclopedia

    Is there anyone here that truly understands all of this that can explain it easily OR can recommend links that explain it clearly?

    My purpose for all of this is I want to understand how computer work. Seriously understand it. I tried to simply study computers as they are now how I know them to be but either that way is far too complicated without background study OR I just had a horrible website/person teaching me. Hopefully there are some confident experts on the matters here.


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    You'll never really get anywhere without some background study. Sometimes there are no shortcuts in life.


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    So, can you assist me here or should I wait for others to come along. I am just so eager to learn I can't hardly stand it. It is just really really difficult to find a forum or resource where someone understands computers to the depth that I am looking for. 99.9% of people just don't care about it that much unfortunately.
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    Brassica oleracea Strange's Avatar
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    I'm not sure that learning the history of computing will really help with understanding the principles behind how they work.

    Part of the problem might be that a processor can be understood at several different levels. For example, you can just think of it as something that executes instructions (add, load, etc). In which case, you probably don't need to know much more than the instruction set description (and the internal registers, etc)

    On the other hand, you might want to know how those instructions make the hardware perform the corresponding functions. In which case you need to look at the microarchitecture: how an ALU can perform different arithmetic and logical operations on data depending on the operation code it is given.

    Or, you might want to know how an ALU or a data register actually work. In which case, you are getting into the details of logic design. But you might want more detail and need to look at transistor-level design...

    Complicated, isn't it!

    Perhaps you could say what you currently understand and where you are having difficulties. Then we might be able to help explain the specific areas you are stuck on.

    (I have designed and programmed microprocessors so I hope I would be able to answer some questions - but I don't really want to write an entire textbook on the subject!)
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    What issues are you having with the Wikipedia article? I briefly reviewed it and thought it was pretty useful, but perhaps if you posted specific questions that you have or specific topics that you don't understand, we can address those? Not sure about everyone else here, but as someone proficient in computing, I'm unsure that I could do better job explaining things than that article, even if I had the time and the patience to do so.

    Unfortunately, there is no "easy explanation" for many advanced and complex topics. I commend you for taking the initiative to educate yourself on one of your interests, but you may need to read beyond that one Wikipedia article to fully comprehend these subjects. If there is a particular term that you don't understand in the article, open a new tab in your browser and define it for yourself before you continue reading. Using Wikipedia can sometimes make this process a little easier, as it conveniently links to many other relevant topics in any given article. When I am using Wikipedia to educate myself about a topic I know little about, I will sometimes have 6 or 7 tabs open before getting through a single paragraph of my original article, but it is completely worth it (and necessary) if you wish to gain a comprehensive understanding of the things that interest you.
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    Before I get into where I am with my study and understanding of this, I would like share with you a project that I did in my community that lit me on fire about learning everything down to the core as if I were going to construct it myself.

    I was taught a bit about geology, mineralogy, stone carving, blacksmithing, metallurgy, woodworking, and masonry. So, we went out and located and identified some minerals, extracted them with some stone tools we carved, smelted them and extracted the metal in the kiln we built and then made tools out of them. It was so exciting and I can't wait to learn more. That project revealed to me up close and personal the history behind how a lot of things are/were made. If I wanted to technically I could make whatever I want to. But I will not mostly because it is time-consuming. Great to know how to do it though nevertheless.

    But I thought why don't I have an understanding of computers like what I had been taught in the above project.

    So, with that said, here is where I am at with this progress of understanding computers (technology):

    a. When I first started this, I quickly realized that I am confused about so much information. Mathematics, computers, science things, and a number of other areas as well. I always read and hear about how math is so important and I really didn’t know why. After looking around online for quite a while, I found this site:
    History of Mathematics - Main Page
    Origins of Mathematics

    I didn’t make it through all 12 chapters because I got confused very quickly since I don’t have a teacher or someone knowledgeable in math to explain things to me. Nevertheless, the first chapter, “The Origins of Mathematics” taught me so much. I wish every subject ever taught was approached from the angle that that first chapter explains the development of mathematics.

    So, from that first chapter I learned that math was developed out of necessity from society. This is how all knowledge (not just math) should be learned. What need in society or daily life invoked the creation of math and each of it’s many concepts, etc.. I learned about the binary system of counting and other base number systems as well.

    I mention the above about math and that site because that established the foundation in the way that I approach the study of any type of mathematics in the future. Which is important if what I have been told about the necessity of learning/knowing math to understand computers. When I inquire about the history behind advanced/complex math then you’ll know where I get this approach from.


    b. After that, I just starting searching Google for “how computer work” type sites. Took me a while again but then I found this site:
    How Computers Work: Microprocessor and Main Memory: Tutorial

    The circuit on the first page explains a lot to me. I feel comfortable about my knowledge of how a battery could be made to understand the diagram. A voltaic pile suffices for me. From my knowledge of geology, mineralogy, and blacksmithing, a voltaic pile in a ceramic container, copper wire, and a metal key strip would not be difficult to make. I know how to make charcoal as well for a charcoal strip instead of a light bulb. (arc lamp)

    I read Roger Young’s entire book but there was quite a bit of it that I didn’t understand.


    c. At the same time I was reading Roger’s book, I also started reading this site to check my knowledge about electricity and circuits as well:
    All About Circuits : Free Electric Circuits Textbooks

    Again, I read about a number of things on that site as well before I got confused. The “static electricity” area did help me to understand just what electricity is though.

    -------------------------

    So, that is what I have read and have been focusing on so far. I know I have not yet posted the specific areas/questions that I have but I wanted to go ahead and post what I have been doing thus far before I start posting the areas that I am confused about. That way, after reading what I’ve posted above, you can say, “You are going at this all wrong.” or “You are on the right track, what areas are confusing you?” I will write down and post my questions now.
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    If you are just starting to understand the basic ideas of electrical circuits then you are quite a long way from understanding computers. However, I quite like the approach that article uses, of using relays to introduce the ideas. That was the first thing I thought of when you mentioned the practical aspects of the subjects that you have learnt so far. However, I found their presentation a bit confusing and slow to get to the point. But maybe for a newcomer it is good.

    The point is, you could build a simple logic circuit, the basis of all computers, from relays (and you could even make the relays yourself if you were that crazy!). In fact, I think that may have been how the first computers were made. They rapidly moved on to electronic valves and then transistors as they are faster and lower power (and smaller). But, in principle, you could build a simple computer from scratch.
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    One thing I believe you would find useful would be to grasp the principals of digital logic and Boolean algebra. I can't recommend any specific sites, but ggogl e shoudl turn up some info. If you have questions based on that I can try to answer - at one time I was competent at troubleshooting elecctronics at the component level, back when a component was a small integrated circuit, not a complex microprocessor; and I used to be able to write machine language code for self diagnostics on mini computers.
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    I am writing still trying to write down the areas that I confused about but I did just see your response, John. I did a quick Google search just to see what sites would pop up and look what I found:
    Building an 8-Bit Computer – Now With Instructions | 8 Bit Spaghetti
    How to Build an 8-Bit Computer

    Looks to be very very interesting and relevant to what I am trying to do. I haven't read through all of it yet since I am in the middle of trying to write my next post here but I just thought I would post those links here. The author just posted his work up last month too! (just in time, maybe)
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    (note: I’ll approach this by just looking at a modern computer and not worrying about the history of computers until one of you recommends that I do some back study to understand a specific area. If this approach doesn’t work then I can post what I’ve learned by studying the history in order to understand the present.) If anything that I post below is incorrect, please let me know.


    The first use of the term computer, one who computes (to determine an amount or number), was as a label for humans who worked as a computer. They determined amounts or numbers using their brains. I’m not sure what kind of work they did though. Wikipedia mentioned mathematics for aerodynamic designs. There has to be a simpler example. Anyway, the human is the entire computer. The hardware is their hands. The software is their means of communication. For example, their language (English, Hindi, Arabic, etc.), their counting system (base 2 [binary], base 10 [decimal], base 16 [hexadecimal], etc.), etc. The data bits (oral information) was stored on memory (brain).

    So, that’s a computer. That is how it works. Now, I move on to understanding each part of a modern computer. You asked what I understand so far. In my above post, I mentioned the battery. I understand how to create a simple battery. That is electricity generated chemically (chemical energy). I understand how turbines work and also generators. A turbine is a device that transforms motion into energy. (flow of water[water wheel]/force of wind[windmill] to mechanical energy, combustion of explosive materials to mechanical energy) A generator is a device that transforms mechanical energy to electricity. (can use the same sources of mechanical energy listed with turbines) A generator would be like two dissimilar metals (zinc and silver) and then a coiled copper wire with other straight copper wire connected to it. The copper wire spins around the two metals and electricity is generated in the wire.

    So, I have a number of options for powering my computer that I understand albeit at a simple level. (that suffices for me since the concepts are the same) I need to understand the parts of the modern computer now individually. I don’t think there is an order to learning these. Just pick one, learn it, and move to the next component/area. I return to Mr. Young’s site with where I learn about microprocessors.

    1. What the difference between a processor and a microprocessor?
    Thoughts: I found this link:
    Difference Between CPU and MicroProcessor | Difference Between | CPU vs MicroProcessor

    I thought I understood the difference until the article stated “All CPUs are microprocessors, but not all microprocessors are CPUs.” But I think the microprocessors that are not CPUs that the article is referencing are the microprocessors that contained CPUs across a number of microprocessors before microprocessors were created with single CPUs on them. This was stated in the article:
    “It has managed to contain the CPU, at first in a couple of microprocessors, then finally into a single microprocessor.” correct?

    2. Why is the diagram on p.7 called an (address) decoder?
    How Computers Work: Memory: Page 7

    Thoughts: I have found two links:
    Address Decoder - Wikileki
    address decoder - Technical definition of address decoder
    Address decoder: Information from Answers.com

    I think there are four different possibilities that can be input by pressing A, B, A and B together, or pressing nothing at all. Each of these three inputs equals a different address (or sequence of lights that will light up) that will be shown when pressed or not pressed. I’m not sure though.

    3. “Truth table” is an arbitrary title taken from another field (Logic) and applied to the electronics definition below:
    “(Electronics) a similar table, used in transistor technology, to indicate the value of the output signal of a logic circuit for every value of input signal”
    truth table - definition of truth table by the Free Online Dictionary, Thesaurus and Encyclopedia.

    Thoughts: I inquire about this because I kept thinking that I was supposed to be getting some extra meaning from the word ‘truth’ in the name but when I looked up what it meant and what it signified then I knew that it was just arbitrarily called a “truth table”.

    4. I don’t understand the title “ROM (Read-Only Memory) With Enable (EN) Key (D)” for what is going on on p.7
    How Computers Work: Memory: Page 7

    Thoughts: I was reading this page:
    How computer memory works: A simple introduction

    But I just still don’t get it at all. However I am not sure if I am supposed to understand what is going on just yet...

    Ok, that’s enough questions for this post. I have more since I have gone over the entire book but I’ll post them slowly so it isn’t too cluttered.
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  12. #11  
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    Quote Originally Posted by doasl View Post
    1. What the difference between a processor and a microprocessor?
    Thoughts: I found this link:
    Difference Between CPU and MicroProcessor | Difference Between | CPU vs MicroProcessor
    That article isn't very well written. I wouldn't worry too much about this question. Nowadays the two terms are used almost interchangeably.

    But, if you want to be precise, the CPU is the bit that does logic and arithmetic operations. In a microprocessor, this is surrounded by circuitry to fetch and decode instructions, peripheral devices to do various forms of input and output of data, memory, possible specialized circuits for 2D and 3D graphics display, etc. etc.
    I thought I understood the difference until the article stated “All CPUs are microprocessors, but not all microprocessors are CPUs.” But I think the microprocessors that are not CPUs that the article is referencing are the microprocessors that contained CPUs across a number of microprocessors before microprocessors were created with single CPUs on them. This was stated in the article:
    “It has managed to contain the CPU, at first in a couple of microprocessors, then finally into a single microprocessor.” correct?
    Neither of those two sentences made much sense to me. The second one isn't even grammatical.

    2. Why is the diagram on p.7 called an (address) decoder?
    The data in a memory is stored in a series of memory cells. The memory is addressed by numeric address (0, 1, 2 ... up to the maximum size of the memory). These addresses are encoded in binary on the address bus. So the two address wires (A and B) can encode four addresses (and hence, access four memory cells):
    AB Address
    00 0
    01 1
    10 2
    11 3

    To use this binary address to access the data in a single memory cell, it has to be decoded to a signal on a single wire that provides access to that cell. So the example above needs to be decoded to one of four wires which each enable reading or writing a single cell.

    The reason for this is to reduce the number of address lines required. Here we access four cells with two address lines. In a realistic processor 32 address lines allow 4 billion memory cells to be accessed. (Note that, in this case, the decoding is slightly more complex.)

    Thoughts: I inquire about this because I kept thinking that I was supposed to be getting some extra meaning from the word ‘truth’ in the name but when I looked up what it meant and what it signified then I knew that it was just arbitrarily called a “truth table”.
    The name comes from the original idea that "Boolean logic" (named after the mathematician/philosopher George Boole) could be used to decide the truth or otherwise of normal language. It was later found to be much more useful! The word has carried over so that we still refer to the values 0 and 1 as "false" and "true".

    4. I don’t understand the title “ROM (Read-Only Memory) With Enable (EN) Key (D)” for what is going on on p.7
    The basic idea of a ROM is that the data is fixed when it is built (unlike a RAM where data can be written as well as read). The address decoder accesses locations which have had values (0 or 1) hard-wired into them. When the enable signal is set to 1, then the addressed value is output. If the enable is 0, then 0 is output. In a real memory, the outputs would be effectively disconnected when enable=0; this allows multiple memories to be connected to the same set of data wires. The enable signals then control which memory device is accessed.

    I have more since I have gone over the entire book but I’ll post them slowly so it isn’t too cluttered.
    You will probably find you need to go over it all once and then again once you have got the basic idea. (That's what usually happens when I ma learning something new.)

    Good luck and hope that helps.
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  13. #12  
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    As a side note, one of the first major users of human computers (way back when) was doing astronomical calculations, for both raw astronomy and navigation.
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    Thank you for your responses, Strange. But it seems like your explanations are a bit complex. I am going to try to break it down to the easiest level to make sure I understand it.

    About the differences between a processor and a microprocessor, I’ll just assume my summary was correct since I don’t think I know enough to understand what you posted (yet).

    I am going to go over your posts before I continue on to my next questions to ensure I know what you are talking about:

    Quote Originally Posted by Strange
    “The data in a memory is stored in a series of memory cells.”
    In the diagram, the data is the sequence of what is pressed down. A, B, both together or neither at all. The memory in the above sentence is just a type of circuit that has loops or a loop. Which means a circuit that is capable of saving data (you input the data [press A, B, or whatever] and the resulting output is saved [this ‘saving’ refers to when the text explained that a key is pressed in a loop and the magnet is energized and the key that was pressed stays pressed down until a force greater than the magnet holding it down changes the state of the key] ) The memory cells are the individual loops that save each bit of data (press only A = one bit of data, press only B = one bit of data, press A & B = one bit of data, both A & B not pressed down = one bit of data that can be saved)

    Quote Originally Posted by Strange
    “The memory is addressed by numeric address (0, 1, 2 ... up to the maximum size of the memory).”
    The memory (the circuit) is given it’s name according to how many addresses that are possible in it. In the case of the diagram, the maximum size of the memory is four addresses therefore that is called a four bit memory circuit. (1. could I also say it’s a four bit memory chip?)

    Quote Originally Posted by Strange
    “These addresses are encoded in binary on the address bus.”
    To start off, I do not know what an ‘address bus’ is. I have looked at some links and this link seems like it helps but I still don’t get it. (I’ll return to this in a bit.)
    Address Bus

    Moving along, with the focus sentence and the page we are discussing (page 7), we have now encountered the two words, encode and decode. According to the definitions of these words:
    encode - definition of encode by the Free Online Dictionary, Thesaurus and Encyclopedia.
    decode - definition of decode by the Free Online Dictionary, Thesaurus and Encyclopedia.

    To encode is to put a ‘plain message’ (language that we, as humans, understand ie English) into code (language that computers understand).
    To decode is put computer language (code) into human language.

    So, I am guessing that when you state ‘addresses are encoded in binary’ this means the addresses could be numbers or letters. For example, if 10 = letter g and 11 = letter o When I write what letters/number (or whatever) 10 and 11 (and also 01, 00 ) represent on the address bus (whatever that is), that means I am encoding the address bus. (2. Is that the way I state it?) So, this encoding process is done when I am creating the circuits and that is why it isn’t listed on page 7. Therefore 1011 would be ‘go’ in our language. I don’t know what an address bus is concerning page 7 and the diagram we are looking at though. I kind of have the feeling that the address bus is the column of four lights I, J, K, L. Each light individually is a memory cell as you wrote but together as a column they are called the address bus. But I’m not sure though.

    So, the decoder that is discussed on page 7 is called such because to retrieve the encoded human language message that I want, I must input the correct corresponding computer language code. It’s called a decoder since it takes that binary input that I press on the circuit with my fingers, decodes it, and gives me (outputs) the encoded message (that I set up when I set up the circuit beforehand). In the case of the diagram on page 7, the encoded message would be output in the lighting up of lights I, J, K, L. 3. Is all of this correct?

    Quote Originally Posted by Strange
    “In a realistic processor 32 address lines allow 4 billion memory cells to be accessed.”
    4. 4,294,967,296 to be exact, right?

    Quote Originally Posted by Strange
    “The name comes from the original idea that "Boolean logic"”
    Oh ok, so it comes from Boolean rules (aka logic). I’ll call it that and move on. Thank you.

    Quote Originally Posted by Strange
    “The basic idea of a ROM is that the data is fixed when it is built”
    Quote Originally Posted by Strange
    “The address decoder accesses locations which have had values (0 or 1) hard-wired into them.”
    I thought ‘having the data fixed when it is built’ in a ROM meant that there is no key (nothing to open or close/no option of false or true value) for a memory cell. There would be nothing to open or close (ie a key), just an address wire going to the memory cell. That is what the definition of hard-wire reads:
    hard-wire - definition of hard-wire by the Free Online Dictionary, Thesaurus and Encyclopedia.

    Hmm, I don’t know if that makes sense, but I am confused. Perhaps if there was diagram to contrast the two specfically (ROM / RAM).

    More thoughts on the above: 5. Wouldn’t I have to know beforehand which values are unchanging? I would be one setting that up, right? Either I am totally lost here or page 7 is not doing a good job at all of explaining this. Is the ‘enable’ key the one key that if pressed enables the read only memory to change? I’m not sure what to make of this.

    Quote Originally Posted by Strange
    “unlike a RAM where data can be written as well as read”
    I don’t think I know what it means ‘to read’ or ‘to write’ to memory regarding what I have been studying so far.

    Quote Originally Posted by Strange
    “When the enable signal is set to 1, then the addressed value is output.”
    6. ‘addressed value’ meaning the value hard-wired when the circuit was built, right?

    Quote Originally Posted by Strange
    “If the enable is 0, then 0 is output.”
    Regardless of the hard-wired value.

    Quote Originally Posted by Strange
    “In a real memory,”
    in other words -> “Contrasting with the learning aid memory diagram we are using to study with, ”

    Quote Originally Posted by Strange
    “this allows multiple memories to be connected to the same set of data wires.”
    This is the first mention of “data wires”. 7. Contrasted with address wires, which we have seen mentioned before, what is their meaning? Seems like it is the same thing as the 'address wires'. If one says 'address wires' then the focus is on the addresses but if one says 'data wires' then the focus is on the 'data'.

    Quote Originally Posted by Strange
    “The enable signals then control which memory device is accessed.”
    I think I understand what this means in a sense because at my dad’s office, he has multiple computers with multiple screens but with one mouse and one keyboard. To toggle between each computer and screen, I have to press a button on some box on his desk. I assume this is referring to something like that. While I understand that, I do not understand this sentence in the context of what we are studying on page 7.

    @MeteorWayne - I was looking more for a simple use(s) that I could do myself. Not too sure about raw astronomy and navigation. But it doesn’t matter though, I was just wondering out loud.
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    The work of Alan Turing occupies a big part of early computer science, he built his own valve based computer from scratch using parts from a telephone exchange.

    Automatic Computing Engine - Wikipedia, the free encyclopedia

    Alan Turing - Wikipedia, the free encyclopedia
    “The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.”

    Bertrand Russell
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    doasl,

    You really need to get a textbook or other book on how computing works. I don't think Strange intends to write one here for you. IMHO.
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    doasl,

    You really need to get a textbook or other book on how computing works. I don't think Strange intends to write one here for you. IMHO.
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    I would love if Strange would recommend a textbook for me that he feels will explain how computers work for the level of detail that I am trying to understand it at. I actually prefer that since it would just allow me to read and understand without typing so much. I hope something like this exists because I have not found anything yet hence why I started this thread and read Roger Young's entire book. I really hope that there is a book or a set of books that can break this down for me. And I hope it is something that whoever recommends it can truly vouch for it. Most people just say the names of random books without knowing anything about them and then after the person has bought them, it turns out to be not good at all and it's a waste of money/time. Any recommendations?
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  19. #18  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by doasl View Post
    About the differences between a processor and a microprocessor, I’ll just assume my summary was correct since I don’t think I know enough to understand what you posted (yet).
    Fair enough. They are used in so many different ways that the original meanings have been pretty much lost now anyway.

    In the case of the diagram, the maximum size of the memory is four addresses therefore that is called a four bit memory circuit. (1. could I also say it’s a four bit memory chip?)
    Correct.

    Quote Originally Posted by Strange
    “These addresses are encoded in binary on the address bus.”
    To start off, I do not know what an ‘address bus’ is. I have looked at some links and this link seems like it helps but I still don’t get it. (I’ll return to this in a bit.)
    Just the set of wires/signals which determine the specific data (memory cell) to be accessed. This is normally encoded as a binary number (0, 1, ... n) and internally is decoded to the single wore to access the memory cell. (Simplifying a bit.)

    To encode is to put a ‘plain message’ (language that we, as humans, understand ie English) into code (language that computers understand).
    To decode is put computer language (code) into human language.
    That is one meaning. In the case of address decoding, it is much simpler: it is just the process of going from the binary address (0, 1, 2, ... n) to a signal which identifies the specific memory cell. In more complex systems there may be multiple levels of this address decoding: first decode the address to determine which type of memory is being accessed (disk, ROM, RAM, etc) then decode the address further to determine which memory chip is being addressed then decode it further (within the selected chip) to get the specific data in a cell.

    So, I am guessing that when you state ‘addresses are encoded in binary’ this means the addresses could be numbers or letters. For example, if 10 = letter g and 11 = letter o When I write what letters/number (or whatever) 10 and 11 (and also 01, 00 ) represent on the address bus (whatever that is), that means I am encoding the address bus. (2. Is that the way I state it?)
    This sort of encoding is more likely to be used for data rather than addresses.

    Quote Originally Posted by Strange
    “In a realistic processor 32 address lines allow 4 billion memory cells to be accessed.”
    4. 4,294,967,296 to be exact, right?
    Correct.

    Hmm, I don’t know if that makes sense, but I am confused. Perhaps if there was diagram to contrast the two specfically (ROM / RAM).
    They are both types of memory. They have a series of locations/cells/whatever that each store a bit of data. In the case of RAM you can specify the address of a cell and the data you want to write into it. Later you can read it back by specifying the same address. (And then you can write new a data value). In the case of a ROM you cannot write data to it, you can only read the data that is in there.

    Is the ‘enable’ key the one key that if pressed enables the read only memory to change?
    The enable signal allows you to access the memory to read the data (at the specified address). In the case of a RAM there will be another signal (write enable) that allows you to write new data into the cell.

    Quote Originally Posted by Strange
    “unlike a RAM where data can be written as well as read”
    I don’t think I know what it means ‘to read’ or ‘to write’ to memory regarding what I have been studying so far.
    Read means to access or get the data stored in the addressed memory cell.
    Write means to change the data stored in the addressed memory cell.

    Quote Originally Posted by Strange
    “When the enable signal is set to 1, then the addressed value is output.”
    6. ‘addressed value’ meaning the value hard-wired when the circuit was built, right?
    Addressed value meaning the value in the cell at the memory address you provide. This will be the fixed (hard-wired) value in the case of a ROM. It will be the last value ou wrote in the case of a RAM.
    Quote Originally Posted by Strange
    “If the enable is 0, then 0 is output.”
    Regardless of the hard-wired value.
    Correct.

    Quote Originally Posted by Strange
    “In a real memory,”
    in other words -> “Contrasting with the learning aid memory diagram we are using to study with, ”
    Correct.

    Quote Originally Posted by Strange
    “this allows multiple memories to be connected to the same set of data wires.”
    This is the first mention of “data wires”. 7. Contrasted with address wires, which we have seen mentioned before, what is their meaning? Seems like it is the same thing as the 'address wires'. If one says 'address wires' then the focus is on the addresses but if one says 'data wires' then the focus is on the 'data'.
    There are three sets of signals connected to a memory:

    Address wires or bus: the signals which specify the memory cell which is to be accessed
    Control signals: determine what the memory will do; for example the "enable" signal will cause it to use the address to access the data in the cell specified by the address, the "write enable" will cause new data to be written to the cell
    Data wires or bus: the wire(s) or signal(s) that return the value(s) in the addressed cell, or that provide the data to be written to the addressed cell.

    Quote Originally Posted by Strange
    “The enable signals then control which memory device is accessed.”
    I think I understand what this means in a sense because at my dad’s office, he has multiple computers with multiple screens but with one mouse and one keyboard. To toggle between each computer and screen, I have to press a button on some box on his desk. I assume this is referring to something like that. While I understand that, I do not understand this sentence in the context of what we are studying on page 7.
    At this stage, you probably shouldn't worry about it. But, just to expand on the idea a bit. The total memory in a computer may be much more than a single memory chip. In this case, part of the address is first decoded to decide which memory chip has the cells being addressed; this generates an "enable" signal for that chip. The remaining part of the address is then used to access the cells within that chip.

    Sorry if some of this doesn't relate to the text you are reading, but I'm afraid I found that approach too confusing. It relies (for me) too much on low level detail (switches, wires, relays) rather than the concepts. I know people learn in different ways: some like to get the "big picture" and then understand the details; others like to understand the details and then how they go together to make the big picture. I am the first type.

    I don't really know any good introductory books, I'm afraid. You might find some of the material here helpful: CSC101 Readings Sections 1 & 2
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    Or some anecdotals from old timers. (Like me!) Stories of being ecisted by a text line editor, writing basic math functions in assembly, visiting an entire warehouse full of file cabinets, full of neatly organized piles of cards that represented early meteorological programs, 16KB/s rubber phone cup connections etc. Friends tell my some of the Fortran 77 cloud radiative transfer subroutines I wrote are still incorporated in the modern models, because they work and there's been no reason to change them. I grew up during that awkward time between teams of 10 pound brains who acted as "computers" to the real things we know today. I don't miss those times, especially the routine 6-8 week waits to get something in the mail because of paper and carbon copy admin time-- and layers upon layers of metadata for find essential documents before we had databases.

    Not sure that helps but perhaps puts some perspective into the history of computing.
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