Differentiate between the various types of memory

Memory is a temporary storage place for data, instructions, and information. Memory stores the operating system, application programs, and the data processed by application programs. A byte is the basic storage unit in memory. Memory size is measured by the number of bytes available for use.

·         A kilobyte (KB or K) of memory is approximately one thousand bytes,

·         a megabyte (MB) is approximately one million bytes, and

·         a gigabyte (GB) is approximately one billion bytes.

The system unit contains several types of memory.

RAM (random access memory) consists of memory chips that the processor can read from and write to. Most RAM is volatile memory, meaning that its contents are lost when the computer’s power is turned off. Two basic types of RAM chips are dynamic RAM and static RAM.

Dynamic RAM (DRAM) must be re-energized constantly or it loses its contents.

Static RAM (SRAM) is faster and more reliable than DRAM and has to be re-energized less often, but it is much more expensive.

Memory cache, also called a cache store or RAM cache, improves processing time by storing frequently used instructions and data.

ROM (read-only memory) refers to memory chips that only can be read and used; that is, they cannot be modified. ROM is non-volatile memory (NVM), meaning that its contents are not lost when the computer’s power is turned off. A variation of the ROM chip, called programmable read-only memory (PROM), is a blank chip on which you can place items permanently.

Flash memory, also known as flash ROM or flash RAM, is non-volatile memory that can be erased electronically and reprogrammed.

Complementary metal-oxide semiconductor (CMOS) memory, another type of memory chip, stores configuration information about the computer and uses battery power to retain information when the power to the computer is off.

Describe the types of expansion slots and cards in the system unit

An expansion slot is an opening, or socket, where you can insert a circuit board into the motherboard. These circuit boards – called cards, expansion cards, boards, expansion boards, adapters, adapter cards, interface cards, add-ins, or add-ons -- add new devices or capabilities to the computer. Four types of expansion cards found in most computers are a video card, a sound card, a network interface card, and a modem card.

A video card converts computer output into a video signal that is sent through a cable to the monitor, which displays an image.

A sound card enhances the sound-generating capabilities of a personal computer by allowing sound to be input through a microphone and output through speakers.

A network interface card (NIC) is a communications device that allows the computer to communicate via a network.

A modem card is a communications device that enables computers to communicate via telephone lines or other means. Many of today’s computers support Plug and Play, a capability with which the computer automatically can configure expansion boards and other devices as you install them.

Notebook and other portable computers have a special type of expansion slot used for installing a PC Card, which is a thin credit card-sized device that adds memory, disk drives, sound, fax/modem, and communications capabilities to a mobile computer.