What is a computer?

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?

Let’s start with a dictionary¶

we can start with a dictionary

• note that this starts with reference to a person.

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

Computers as Machines¶

Computers as machines started later. We started with mechanical, analog and then moved to electronic and then digital.

How much do we talk about computers?¶

how much do we talk about them changes over time

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 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

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

How to store a value¶

We need a few more components:

• mux select one of two values

• flip-flop hold a value until told otherwise

register

Registers give us SRAM which can hold a value as long as the system has power

another way to physically store a value¶

DRAM uses one transistor and one capacitor. (SRAM uses 4-6 transistors)

a capacitor holds a charge for a time, but gradually fades, so it has to be refreshed

ROM is a diode matrix traditionally

• hardward encodes the instructions

• cannot be changed without rewiring

PROM¶

• can be reprogrammed once after device is made

• used for firmware/microcode

(programmable ROM)

EPROM or EEPROM¶

• treated like ROM

• can be erased & reprogrammed

• but not infinitely, very limited number of tmes

• holds value when power goes away, UV light or electriciy can re-program

SRAM:¶

• is volatile; it needs power to hold a value

• is fast

• takes up more space on the chip (uses 4-6 transistors per bit)

• typically used of cache and internal registers

DRAM:¶

• is volatile; it needs power to hold a value

• is slower and requires a refresh

• is small (1 transistor + 1 capacitor per bit) and space efficient

• used for the main RAM

Flash memory¶

• non-volatile; holds a value without power, can be electircally erased and re-programmed

• comprised of memory “cells” in layerd boards

• memory cells are mosfets - a different type of transistor that retains a state after power is removed and put bag

• implemented with EEPROM

• designed for large blocks and limited writes (~10k)

• used for ssd, usb flash drives, smartphones, etc

• slow to write, fast to read

Prepare for Next Class¶

1. think about what you know about networking

2. make sure you have putty if using windows

3. get the big ideas of hpc, by reading this IBM intro page and some hypothetical people who would attend an HPC carpentry workshop. Make a list of key terms as an issue comment

Badges¶

Experience Report Evidence¶

Questions After Today’s Class¶

Do you think that the heights we have hit now with computers is what the forefathers imagined?¶

It might be what some imaginged, but others definitely wanted more things to be free and open source.

How was there enough technolgy to make tvs back in the day but yet computers were huge and not that advanced?¶

TVs also used vacuum tubes and were also pretty big. Additionally, the content the TV showed was analog.

ow much farther do you think we can push memory and overal storage for personal computers? Is there a limit we will hit?¶

I don’t have a good answer for this, but it is a good explore badge topic.

Are there more computer history museums beyond the ones in North Kingstown and California?¶

A wikipedia article has tabulated a large global list.

How much more can computers improve? is there a limit, and are we approaching it?¶

There are limits in some aspects, for example, Moore’s Law, which said the number of transistors would double every two years, may be over. We can’t make things smaller, past a certain point, but other changes could happen.