| | | |  RAM | | | | Random Access Memory. Solid state storage medium taking the form of a number of integrated circuits (ICs) or silicon chips, mounted on PCBs (Printed Circuit Boards). Ordinarily RAM is not mounted permanently on the motherboard of a personal computer but is installed separately in a number of discrete slots. The exception of this is the memory associated directly with the processor or "cache", which is onboard the CPU (central processing unit) itself. Data storage in RAM is short-term in that it is only held there as long as there is power to the computer. When the power is turned off it is lost, in contrast to long-term storage media such as ROM (Read Only Memory), magnetic HDDs (hard disk drives), optical disks and magnetic tape media. RAM is "random access" because data stored can be accessed in any order, not just sequentially, and with no relationship necessary between one piece of data and the next. Access time is not related to the physical position of the data because there are no moving parts, unlike other storage media such as tapes and hard disk drives where mechanical movement is required, which is the slowest part of the access procudure. Because of it's speed, RAM is used as primary storage for applications currently in use (including the operating system), data being handled and images to be displayed. In most common usage, RAM refers generally to DRAM, or Dynamic RAM, so called because it needs to be refreshed thousands of times per second. Unlike other storage media, when "full" RAM is still able to handle more data, however in order to do this the processor must continually go back and forth to other media (normally a hard drive) in order to use "virtual memory" (an area set aside on the hard drive for this purpose) so that it can overlay new data over old in the RAM. This greatly slows down the running of the computer and is often an indicator that more RAM should be installed. | | | | | | CMOS | | | | Complementary Metal Oxide Semiconductor. This term, "metal oxide semiconductor" refers to the physical structure found in some field effect transistors - a metal gate electrode set on top of an oxide insulator, on top of a semiconducting material. A very widely used silicon and germanium based integrated circuit (IC) design, almost ubiquitous across all electronic products - most modern chips (termed "die" or "dice" in the industry) are now constructed on the CMOS basis. The CMOS IC is a type of transistor that, unlike other transistors, uses a combination of both NMOS (negative polarity) and PMOS (positive polarity) circuits connected together. Only one of these circuit types is on at a particular time (CMOS circuits dissipate power only when switching), meaning that a CMOS chip uses less power than an equivalent NMOS or PMOS chip and is very efficient, also emitting less energy in the form of waste heat. As a result of the latter, certain CMOS chips can run very fast without risking heat damage. CMOS circuitry is more dense than other design types with the same functionality. The charge in the circuit can also stay in one state over an extended period of time. CMOS circuits also show a high level of immunity to electronic noise. All of this makes CMOS ICs ideal for use in battery powered devies such as laptop PCs and PDAs for example. CMOS memory is also used in PCs (and other devices) to store critical low-level system information such as system setup data and the time and date, where the minimal current drain on a small lithium ion "CMOS battery" on a motherboard (for example) can keep this data safe for many years. | | | | | | Operating System | | | | Sometimes shortened to OS. The software that controls the way the resources and internal tasks of a computer are managed. It is the first program to be loaded on switching on the machine, when the computer boots. The most basic part of the OS, the "Kernel" then remains resident in memory at all times. It interfaces between the hardware and the application programs running on the computer through the Application Program Interface (API), making requests for services, meaning that software developers do not have to account for interacting directly with every possible version of hardware as this is taken care of by the OS. Users interact with the operating system through either a Command Line Interface (CLI) or, more commonly now, a Graphical User Interface (GUI). The former relies on typing commands in directly from the keyboard in a text-only format and has a very basic appearance, whereas the latter uses mouse/stylus input too and the user can be separated from direct interaction at the command level by a variety of more visually appealing interfaces. The most commonly used operating systems today are Microsoft's Windows family, Linux and Unix-based systems and Mac OS X. Services performed by the operating system for application programs include: i) the prioritisation of applications in a multi-tasking environment, ii) management of memory resources, iii) communication with peripheral devices through "Drivers" (a generic or "abstracted" way of controlling each type of device by the operating system is interpreted for the specific device in question by the driver, which is a series of instructions writen for that piece of hardware in particular), iv) management of data storage (on hard disk drives, optical storage media and tape etc), v) networking requirements, including the TCP/IP protocol and others. | | | |
|
