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1. bit   2. Byte   3. Code   4. Data   5. Program   6. Chip   7. CPU   8. RAM   9. ROM   10. Computer   11. Peripheral   12. System


RAM
Chip that Temporarily Holds Instructions & Data - main memory.
Acronym: Ra = ct-THID-mm (pronounced See-tee THID em-em).

RAM (ram) is an acronym for Random Access Memory, also known as main memory.

Don't confuse the English definition of memory with the Computerese definition. Although you might think of memory as something that is soft or intangible, RAM consists of chips, and chips are hardware--as are your brain cells (no matter how "soft" they seem!). It's the instructions/data held in RAM chips and the thoughts held in your brain cells that are software.

But as with thoughts held in brain cells, instructions/data held in RAM chips can be forgotten. RAM is absolutely vital for computer operations, but its temporary nature also makes it the primary source of data loss.

When you type on a keyboard or perform a mouse action, you are actually resetting RAM switches inside the computer. RAM switches hold your instructions and data until the CPU fetches them for processing. RAM switches then hold the processed information until you store it permanently on disk.

 

The next time you type on a computer keyboard, imagine your hands reaching inside the computer and manually resetting hundreds of switches to match the 0s and 1s of your instruction and data.


Sometimes RAM is called primary storage, although it's best to avoid calling it such. When you use the term "storage," use it only in reference to disk storage (which ironically is sometimes called disk memory!) Disks are more properly called "storage" devices, since they store the switch settings that were created in RAM memory. BrainAid: diSk = Storage; raM = Memory.

RAM Features

Random Access
This means the CPU has random, or non-sequential, access to instructions/data on any part of the RAM chip. It's comparable to a phonograph record--you can directly place the needle on any part of the record you want. In contrast, sequential access, as in magnetic tape, requires you to fast forward or rewind to get to the instructions or data you want.

Read/Write
This means the CPU can read existing data in RAM and write new data to RAM.
* Read = sense the current switch settings.
* Write = change the current switch settings.

 
Volatile (VAWL-uh-tul or VAWL-uh-TIIL)
Volatile means temporary or unstable. With current technology, RAM requires constant power to hold its switches On. When you lose power, even for a fraction of a second, all switches turn Off. When all switches turn Off, the Off/On patterns representing your instructions and data are lost. This volatile or temporary nature makes RAM potentially dangerous--so I encourage you to form the habit of saving your data to magnetic disk every few minutes!


Speed
This is measured in nanoseconds (NA-noh-SEK-unts), abbreviated "ns" which are billionths of a second.

Capacity
This is measured in bytes. In general, more RAM means faster performance. The more instructions/data you can fit in RAM, the less your CPU will have to get them from the relatively slow disk.

RAM & Power Loss
1. With no power, observe the two RAM switches in Off position, representing no data.
2. When power is on, observe the dark RAM switch being set to On to represent data.
3. With the power again off, observe the dark RAM switch returning to Off, losing the data pattern.

 

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