21. What is a computer?#
++{“lesson_part”: “main”}
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?
21.1. Let’s start with a dictionary#
we can start with a dictionary
note that this starts with reference to a person.
21.1.1. 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
21.1.2. Computers as Machines#
Computers as machines started later. We started with mechanical, analog and then moved to electronic and then digital.
21.1.3. How much do we talk about computers?#
21.2. 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
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 royal privilege from France in 1649 to be only person allowed to build a manufactured Computing a calculator is like mechanical calculators
Contrast this royal privelege with the 1970s where in resolving some other conflict, a court that declared the content of the computer cannot be copyrighted and it’s free for anyone to use the concept of a computer
21.3. How did this change over time?#
calculators that are still analog so they’re still working with mechanical systems using Waze electricity becomes easier
21.4. Timeline of Computing#
21.4.1. 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
21.5. Early Computers#
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
21.6. von Neumann Architecture#
21.7. 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.
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
21.8. Prepare for Next Class#
Trace through the ripple carry adder to see how different calculations take different amounts of time.
come up with 2 example addition problems that demonstrate how much the time can vary(one short, one long), comment on this issue and have them ready at the start of class.
hint use electron mode instead of immediate and it will count. There is also a “reload” button that will reset the counter.
21.9. Badges#
Pick a component that is in the more detailed von Neumann (other than the ALU) and contribute an explanation of what it is to your group repo. Coordinate with your team so that each contribution is a different component by creating an issue stating what you will work on before contributing. Link to your PR in the group repo in your badge PR. All contributions should include a description of the component- what it does and how it is built- and it’s predecessors. All must include sources as markdown links.
review a classmate’s PR providing feedback and either approving or requesting changes
Work with your group mates to ensure both your PR and the one you reviewed get approved and merged.
Pick a component that is in the more detailed von Neumann (other than the ALU) and contribute an explanation of what it is to your group repo. Coordinate with your team so that each contribution is a different component by creating an issue stating what you will work on before contributing. Link to your PR in the group repo in your badge PR. All contributions should include a description of the component- what it does and how it is built- and it’s predecessors. All must include sources as markdown links.
review a classmate’s PR providing feedback and either approving or requesting changes
Work with your group mates to ensure both your PR and the one you reviewed get approved and merged.
Read about systems abstractions in CACM and answer reflection questions below in systemsabstractions.md based on the systems abstraction reading:
1. What are your overall thoughts on this article? (include how much is neew vs familar, easy vs hard to understand, etc)
2. How has you undertanding of these changed during this course.
3. Do you think you understand this article more now than you would have at the beginning of the semester
4. Write 3 questions and their answers that could be a quiz to see if someone understood or had misconceptions about the abstractions in this article.
21.10. Experience Report Evidence#
read through the timeline, add reflections on what historical facts are most interesting and what parts of vonn neuman architecure you are not familiar with.