Computer Memory - History, Timeline and More

Computer Memory - History, Timeline and More Drum memory, an early form of computer memory, used the drum as a working part,  with data loaded to the drum. The drum was a metal cylinder coated with a recordable ferromagnetic material. The drum also had a row of read-write heads that wrote and then read the recorded data. Magnetic core memory (ferrite-core memory) is another early form of computer memory. Magnetic ceramic rings called cores, stored information using the polarity of a magnetic field. Semiconductor memory is computer memory we are all familiar with, computer memory on an integrated circuit or chip. Referred to as random-access memory or RAM, it allowed data to be accessed randomly, not just in the sequence it was recorded. Dynamic random access memory (DRAM) is the most common kind of random access memory (RAM) for personal computers. The data the DRAM chip holds have to be periodically refreshed. Static random access memory or SRAM doesnt need to be refreshed. Timeline of Computer Memory 1834 - Charles Babbage begins to build his Analytical Engine, a precursor to the computer. It uses read-only memory in the form of punch cards. 1932 - Gustav Tauschek invents drum memory in Austria. 1936 - Konrad Zuse applies for a patent for his mechanical memory to be used on his computer. This computer memory is based on sliding metal parts. 1939 - Helmut Schreyer invents a prototype memory using neon lamps. 1942 - The Atanasoff-Berry Computer has 60 50-bit words of memory in the form of capacitors mounted on two revolving drums. For secondary memory, it uses punch cards. 1947 - Frederick Viehe of Los Angeles applies for a patent for an invention that uses magnetic core memory. Magnetic drum memory is independently invented by several people: An Wang invented the magnetic pulse controlling device, the principle upon which magnetic core memory is based.Kenneth Olsen invented vital computer components, best known for Magnetic Core Memory Patent No. 3,161,861 and as being the co-founder of Digital Equipment Corporation.Jay Forrester was a pioneer in early digital computer development and invented random-access, coincident-current magnetic storage. 1949 - Jay Forrester conceives the idea of magnetic core memory as it is to become commonly used, with a grid of wires used to address the cores. The first practical form manifests in 1952-53 and renders obsolete previous types of computer memory. 1950 - Ferranti Ltd. completes the first commercial computer with 256 40-bit words of main memory and 16K words of drum memory. Only eight were sold. 1951 - Jay Forrester files a patent for matrix core memory. 1952 - The EDVAC computer is completed with 1024 44-bit words of ultrasonic memory. A core memory module is added to the ENIAC computer. 1955 - An Wang was issued U.S. patent #2,708,722 with 34 claims for magnetic memory core. 1966 - Hewlett-Packard releases their HP2116A real-time computer with 8K of memory. The newly formed Intel starts to sell a semiconductor chip with 2,000 bits of memory. 1968 - USPTO grants patent 3,387,286 to IBMs Robert Dennard for a one-transistor DRAM cell. DRAM stands for Dynamic RAM (Random Access Memory) or Dynamic Random Access Memory. DRAM will become the standard memory chip for personal computers replacing magnetic core memory. 1969 - Intel begins as chip designers and produces a 1 KB RAM chip, the largest memory chip to date. Intel soon switches to being notable designers of computer microprocessors. 1970 - Intel releases the 1103 chip, the first generally available DRAM memory chip. 1971 - Intel releases the 1101 chip, a 256-bit programmable memory, and the 1701 chip, a 256-byte erasable read-only memory (EROM). 1974 - Intel receives a U.S. patent for a memory system for a multichip digital computer. 1975 - Personal consumer computer Altair released, it uses Intels 8-bit 8080 processor and includes 1 KB of memory. Later in the same year, Bob Marsh manufacturers the first Processor Technologys 4 kB memory boards for the Altair. 1984 - Apple Computers releases the Macintosh personal computer. It is the first computer that came with 128KB of memory. The 1 MB memory chip is developed.

How to Separate Salt and Sand †3 Methods

How to Separate Salt and Sand - 3 Methods One practical application of chemistry is that it can be used to help separate one substance from another. The reasons materials may be separated from each other is because there is some difference between them, such as size (separating rocks from sand), state of matter (separating water from ice), solubility, electrical charge, or melting point. Separating Sand and Salt Students are often asked to separate salt and sand to learn about mixtures and to explore the differences between forms of matter that can be used to separate mixture components.Three methods used to separate salt and sand are physical separation (picking out pieces or using density to shake sand to the top), dissolving the salt in water, or melting the salt.Probably the easiest method to separate the two substances is to dissolve salt in water, pour the liquid away from the sand, and then evaporate the water to recover the salt. Physical Separation of Salt and Sand Since both salt and sand are solids, you could get a magnifying glass and tweezers and eventually pick out particles of salt and sand. Another physical separation method is based on the different densities of salt and sand. The density of salt is  2.16  g/cm ³ while the density of sand is 2.65  g/cm ³. In other words, sand is slightly heavier than salt. If you shake a pan of salt and sand, the sand will eventually rise to the top. A similar method is used to pan for gold, since gold has a higher density than most other substances and sinks in a mixture. Separating Salt and Sand Using Solubility One method of separating salt and sand is based on solubility. If a substance is soluble it means it dissolves in a solvent.  Salt  (sodium chloride or NaCl) is an ionic compound that is soluble in water. Sand (mostly silicon dioxide) is not. Pour the salt and sand mixture into a pan.Add water. You dont need to add a lot of water. Solubility is a property that is affected by temperature, so more salt dissolves in hot water than cold water. Its okay if the salt doesnt dissolve at this point.Heat the water until the salt dissolves. If you get to where the water is boiling and there is still solid salt, you can add a bit more water.Remove the pan from heat and allow it to cool until its safe to handle.Pour the salt water into a separate container.Now collect the sand.Pour the salt water back into the empty pan.Heat the salt water until the water boils. Continue boiling it until the water is gone and youre left with the salt. Another way you could have separate the saltwater and sand would be to stir up the sand/saltwater and pour it through a coffee filter to capture the sand. Separating Mixture Components Using Melting Point Another method to separate components of a mixture is based on melting point. The melting point of salt is 1474 °F (801 °C), while that of sand is  3110 °F (1710 °C). Salt becomes molten at a lower temperature than sand. To separate the components, a mixture of salt and sand is heated above  801 °C, yet below  1710 °C. The molten salt may be poured off, leaving the sand.  Usually this in not the most practical method of separation because both temperatures are very high. While the collected salt would be pure, some liquid salt would contaminate the sand, like trying to separate sand from water by pouring off water. Notes and Questions Note, you could have simply let the water evaporate from the pan until you were left with the salt. If you had chosen to evaporate the water, one way you could have sped up the process would have been to pour the saltwater into a large, shallow container. The increased surface area would have exchanged the rate at which water vapor could have entered air. The salt did not boil away with the water. This is because the boiling point of salt is much higher than that of water. The difference between boiling points can be used to purify water via distillation. In distillation, the water is boiled, but is then cooled so it will condense from vapor back into water and can be collected. Boiling water separates it from salt and other compounds, like sugar, but it has to be carefully controlled to separate it from chemicals that have lower or similar boiling points. While this technique can be used to separate salt and water or sugar and water, it would not separate the salt and sugar from a mixture of salt, sugar, and water. Can you think of a way to separate sugar and salt? Ready for something more challenging? Try purifying salt from rock salt.