"how punched cards were used" The first use was in tabulating the census of 1910, I think that was the year. They were invented by James(?) Hollerith. I am looking at a punched card right now. The card was divided into rows and columns.
There were 80 columns and I think 12 rows, the top 3 rows were called zones and indicated how the remaining rows were encoded.
Each column could be a letter(A - Z) or decimal number/(0 - 9). There are 26 letters so each zone punch along with one of the lower 9 was one of 9 letters -- 3 zones times one of 9 lower rows covered the 26 letters. I think this is accurate, no punch was zero and a punch in a lower row was 1 - 8. The cards were read by having a spring loaded contact that would fall through the hole so that whichever made contact that would be the meaning of the punched hole.
What are the engineering and design challenges in creating successful IoT devices? These devices are usually small, resource-constrained electronics designed to sense, collect, send, and/or interpret data. Some of the devices need to be smart enough to act upon data in real time, 24/7. Are the design challenges the same as with embedded systems, but with a little developer- and IT-skills added in? What do engineers need to know? Rick Merritt talks with two experts about the tools and best options for designing IoT devices in 2016. Specifically the guests will discuss sensors, security, and lessons from IoT deployments.