Memory Unit I
Types of Memory
There are two main types of memory and they are:
1. Primary memory (Main memory)
2. Secondary memory (Auxiliary storages devices)
1. Primary memory (Main Memory): This is also called real memory or immediate access store. It holds data, instructions and any results waiting output to the output devices (Such as monitor, printer, etc).Main memory is the fastest storage device but it is expensive to manufacture.
The main memory is divided into two main parts:
i. Read Only Memory (ROM)
ii.Read Access Memory (RAM)
i. Read Only Memory (ROM): This is the permanent place of storage of instructions and programs for starting, testing and controlling of the operations of the computer. This is a pre-installed instruction by the manufacturers.
The content of the ROM is a non-volatile storage; the content can only be read but cannot be altered .Therefore is regarded as Read Only Memory
ii.Read Access Memory (RAM): This takes a dominant part of the main memory. The storage of currently worked application programs and data is carried out on it. The content of RAM is over-written by incoming ones after actions on the previous ones have been completed. This stores temporarily as the content on it is destroyed when switched off. It is therefore said to be volatile storage.
2. Secondary memory (Auxiliary storage devices): This can be regarded as any form of memory other than the main memory.
i. Hard Disk: Hard disks are normally fixed permanently inside the computer, but in the recent times there are external hard disks of high capacity as well. The first hard disk was made by IBM in 1973.It was a 30MB monster with 16-inch platters called Winchester. The storages capacities of hard disk have increased recently that it can hold up to 800 GB of data.
ii. Flash drive/Disk: These are old storage device that are used to make backups or duplication of files. These come in various sizes such as 3 ½ or 3.5 inch type and 5 ¼ or 5.25 inch type.
iii.Compact Disk (CD) /Digital Video Disk (DVD): CD/DVD drive is another storage that can read from or write to a CD disc. It comes in three different types such as CD-ROM, CD-R,CD-RW,DVD-ROM,DVD-R,DVD-RW etc.
Differences between Primary and Secondary Memory
Primary Memory |
Secondary Memory |
1.This is volatile
2.This is a Temporary Memory
3.Higher than HDD/Secondary Memory
4.Primary memory is directly accessible to the CPU
5.The memory devices used for primary memory are semiconductor memories 6.Primary memory is known as main memory
|
This is Non-volatile
This is a Permanent Memory
Lower Than primary Memory
Secondary memory is not directly accessible to the CPU
The secondary memory devices are magnetic and optical memories Secondary memory is known as additional memory or back memory |
Tests and Exercises
1. The Primary memory can also be regarded as ________
a. Control unit b. Main memory c. ALU d. All of the above. Answer: Main memory
2. Which of the following is also classified as temporary memory
a. Primary Memory b. Secondary memory c. Micro chips d. None of the above Answer: Primary memory
3. The main memory type that cannot store information when the computer is switched off is
a. ROM b. RAM c. Auxiliary storage devices d. All of the above Answer: RAM
4. Which of the following secondary memory has the highest storage capacity?
a. Compact disk b. Flash disk c. Hard disk d. None of the above. Answer: Hard disk
5. The main memory categories that take the dominant part is known as ______
a. RAM b. ROM c. EPROM d. EEPROM. Answer: ROM
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