Computer Basic Lesson 24- The Sharing
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Earlier we focus on how computers, how to read and write data from memory, perform operations such as adding two numbers together.
Also briefly talked about the next instruction, which is a computer program.
But we have not talked about is: how the program "into the" computer.
01
Machine programming needs
You should remember that earlier, we talked about a step by step example of a program, then the sake of simplicity, we assume that the program has been magical in memory, but the fact is that the program needs to be loaded into memory, it's not magic, computer science!
The demand for machine programming, long before computers appeared there.
The most famous example from the textile industry, if you just want to weave a big red tablecloths, red line can be placed directly into the loom. But if you want to design how to do? Such as striped or checkered, workers have to be adjusted once every moment looms, because it is very labor consuming, so the pattern textile expensive, there is no specific location perforation determines the line is high or low, from the upper horizontal line is through / from. To make each row of different patterns, even paper cards into strips to form a continuous instruction, sound familiar? Many people think Jacquard loom was the first programming .
02
Perforated paper card for census
Facts have proved perforated paper card is cheap, reliable, and easy to understand.
After nearly a century, punched paper cards for the 1890 United States Census, we mentioned in the first section, a card store a person's information, such as race, marital status, number of children, country of birth and so on.
For each question, the corresponding position census workers will punch, when the card insertion machine summary, the corresponding holes will sum value +1. The card can be inserted into the entire population of the country, to get each worth at the end.
It is worth noting that the machine is not a summary of early computers, because they only do one thing - aggregated data, the operation is fixed and can not be programmed. Perforated paper card data is stored, not the program.
03
Plug plate
After 60 years, these machines are strengthened, you can do subtraction, multiplication, division, or even make some small decisions, decide when to execute a command. In order to properly perform different calculations, programmers need some kind of control panel. There are many small jack panel, the programmer can insert wire, so that different parts of the machine and transmit the data signals to each other, it is also called " patch panel ."
Unfortunately, this means running different programs to re-wiring, so to the 1920s, into a control panel pluggable. Make programming more convenient, you can insert different programs to the machine.
For example, a patch panel sales tax calculation, another payroll calculation, but a very complex programming patch panel, a line drawing mess. The total count is responsible for profit and loss accounts for the IBM 402 machine.
In the 1940s that it is very popular, not only popular in electromechanical computer with a patch panel programming, the world's first general-purpose computer, ENIAC , completed in 1946, with a lot of power strip. After a good program design on paper, to the ENIAC connection, it may take up to three weeks.
Since early computers are very expensive, only a few weeks off for the exchange program, totally unacceptable. People need faster and more flexible new approach to programming.
04
Stored program computer
Fortunately, the late 1940s to early 1950s, the memory becomes lower prices, increased capacity. Rather than present the program strip, in memory becomes possible. This program easy to modify, easy to read fast CPU, this type of machine is called "stored program computer."
If enough memory, you can not only save the program you want to run, you can also store the data required for the program, including new data generated by the program is running, the program and data are present in one place, called "von Neumann architecture" . Named from John von Neumann, an outstanding mathematician and physicist involved in the Manhattan Project and the early computer project.
He said: I was thinking of something much more important than bombs - the computer.
Von Neumann computer flag is a processor (with an arithmetic logic unit) data registers + + + instruction register + memory instruction address register (data and instructions stored in charge). I hope this sounds familiar, because earlier we made a von Neumann computer. The first Von Neumann architecture "stored program computer", the construction done by the University of Manchester in 1948, nicknamed "Baby." Even now you see the video of the computer, but also with the same architecture.
The next section we continue to talk.
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