Computer+Memory


 * __Computer Memory__**

The major hardware components of a computer system are: Bits and Bytes Kilobytes, megabytes, gigabytes Main memory Secondary memory
 * Processor
 * Main memory
 * Secondary memory devices
 * Input/output devices

Example: If you bought a new computer, about how much main memory would you expect it to have: 256 bytes, 256 kilobytes, or 256 megabytes? A new PC should have at least 256 megabytes, and more if possible. PCs have several gigabytes of main memory.


 * Main memory** is as vital as the processor chip to a computer system. Fast computer systems have both a fast processor and a large, fast memory. Some characteristics are true for both kinds of memory; others are true for just one.

Very closely connected to the = True for Main Memory processor.
 * Characteristics**

Holds programs and data that the = True for Main Memory processor is actively working with.

Used for long term storage. = True for Secondary Memory

The processor interacts with it = True for Main Memory millions of times per second.

The contents is easily changed = True for both Main and Secondary Memory

Relatively huge capacity. = True for Secondary Memory

Fast access. = True for Main Memory

Slow access. = True for Secondary Memory

Connected to main memory. = True for Secondary Memory

Holds programs and data. = True for both Main and Secondary Memory

Usually its contents are organized = True for Secondary Memory into //files//.

One bit of information is so little that usually computer memory is organized into groups of eight bits. Each eight bit group is called a byte. When more than eight bits are required for some data, a whole number of bytes are used. One byte is about enough memory to hold a single character. Often very much more than eight bits are required for data, and thousands, millions, or even billions of bytes are needed.
 * Byte**

Main memory consists of a very long list of bytes. In most modern computers, each byte has an //address// that is used to locate it. The picture shows a small part of main memory: Each byte has an address. The addresses for most computer memory start at 0 and go up in sequence until each byte has an address. Each byte contains a pattern of eight bits. When the computer's power is on, every byte contains some pattern or other, even those bytes not being used for anything. The address of a byte is not part of its contents. When the processor needs to access the byte at a particular address, the electronics of the computer "knows how" to find that byte in memory.
 * Main Memory**

"Stores Files" Hard disks (and other secondary memory devices) are used for long-term storage of large blocks of information, such as programs and data sets. Usually disk memory is organized into **files**.
 * Hard Drive**