Random Access Memory (RAM) Read Only Memory (ROM) & Flash Memory
RAM as we know it in 2002
Random Access Memory (RAM) is the main 'working' memory used by the computer. When the operating system loads from disk when you first switch on the computer, it is copied into RAM. The original IBM PC could only use up to 640 KB of memory (just over half a megabyte), whereas a modern computer can effectively house as much RAM is you can afford to buy! Commonly 2002 computers were supplied with over 256MB of RAM and the latest fastest RAM is known as DDRAM but this has been superceded. In 2009 2 to 4 gb of RAM is common with faster architecture DDR3.
Data and programs stored in RAM are volatile (i.e. the information is lost when you switch off the computer).
Read Only Memory (ROM) as the name suggests is a special type of memory chip that holds software that can be read but not written to. A good example is the ROM-BIOS chip, which contains read-only software. Often network cards and video cards also contain ROM chips. Unlike RAM
a/ It can't be written to without special programs or equipment
b/ It keeps its info all the time even when the computer is switched off.
The 'Read Only Memory Basic Input Output System' chip is a chip located on the computer's system (mother) board, which contains software. This software performs a variety of tasks. When you first switch on the computer the ROM-BIOS software performs a self-diagnostic to check that the computer is working OK. This software then loads your operating system from the disk into the RAM. flash BIOS? Most modern computers are actually supplied with a flash BIOS rather than a ROM-BIOS. This chip contains exactly the same type of in-built software, but has the advantage that the software on the chip can be upgraded. This upgrade is achieved by simply running a small program supplied by the computer manufacturer. Any updated information is maintained by a small battery in the Motherboard.
Video (graphics) memory-- The picture that you see on your screen is a form of data and this data has to be stored somewhere. The on-screen pictures are held in special memory chips called video memory chips, these chips are usually located on the video card. A modern computer will be supplied with many Megabytes or Gigabytes of video memory.
Memory is measured in Bits - the bits & bytes page covers this in detail.