High vs low electrical voltage is in some sense the universal language for binary values in a computer. This last part is important as the majority of high speed devices, like RAM and CPUs, used in a computer use electricity (or in some cases light). Further the devices can be controlled and accessed through electrical signals. The CPUs have direct electrical connectivity to RAM which serve as the working memory for the active programs running on our computers.įrom our perspective, the key point is that regardless of the technology, storage devices can be abstractly thought of as a fixed size array of units that can take on one of two distinct states. These components are often called the Memory or RAM (Random Access Memory) of our computers. However, unlike Hard drives, SSDs, and USB sticks, devices composed of these chips can be written and read very fast using electrical voltages on wires that are directly connected to them. If electricity is lost, eg your battery dies, then their values are lost. Other devices such as memory “chips” use cells that actively consume electricity to maintain their values. Depending on the technology used, the cells might represent states using electrical charge or changes in their electrical resistance. No head is required for these devices as the cells can be directly accessed. Modern Solid State Drives (SSDs) and things like “USB sticks” contain electrical cells that serve as their units. Similarly an electrical signal can be used to direct it to set the polarity if desired. When reading, it generates either a high or low voltage on a wire depending on the polarity of the region. Writing means setting the regions polarity to north or south and reading means detecting the regions current polarity. Integrated into these devices is one or more electro-magnetic heads that can “write” or “read” a region, when the region is below them. By dividing the surface into non-overlapping regions, we form units that individually and independently can have their magnetic polarity changed and detected. In these devices a surface is coated with a magnetic material. Some devices, such as older hard drives, use magnetic polarity - north vs south magnetic force. Depending on the device, various different physical mechanisms can be used to represent the values. Bi-stable means that each unit within the collection can reliably be in one of two distinct states. The pattern is a fixed size collection of bi-stable physical units. In general most physical components of a computer store, transmit, or operate on a pattern of binary values. Representing information - Preliminaries: Bits, Bytes and Notation # Program Anatomy IV: The Tree of Bytes and Data Structuresġ7. Information Representation - Native TypesĢ2. Representing information - Preliminaries: Bits, Bytes and Notationġ8. Machine Debuggers & Open Process Surgeryġ7. The Belly of the Beast: The von Neumann Architecture and Assembly Programmingġ5. The Shell - Part I: Having an ASCII conversation with the OSĥ. Organizing and Managing Information as a Tree of Files and DirectoriesĤ. What is a Terminal and why do we still use them?ģ. Under the Covers : The Secret Life of SoftwareĢ.
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