44 total
By the end of this subtopic, you should be able to:
show understanding of why computers need input, output, primary memory, and secondary storage, including removable storage
show understanding of embedded systems, including their benefits and drawbacks
describe the principal operations of these hardware devices:
show understanding of the use of buffers
explain the differences between RAM and ROM, including how they are used in different devices and systems
explain the differences between SRAM and DRAM, including where each is used and why one may be chosen over the other
explain the difference between PROM, EPROM, and EEPROM
show understanding of monitoring systems and control systems, including:
A computer system works by taking in data, processing it, storing it, and producing results. For this to happen, the computer needs several main parts working together. These are input, output, primary memory, and secondary storage.
Input is any data or instruction entered into a computer. A computer cannot do useful work unless it is given something to process. This is why input is needed.
Input can come from a person, from another device, or from the environment. For example:
Without input, a computer would have no facts, no instructions, and no commands to work with.
After a computer has processed data, it needs to show the result. This is called output.
Output is needed because users must be able to understand the result of the processing. For example:
Without output, the computer might process data correctly, but the user would not know what the result was.
Primary memory is memory that the CPU can access directly. It is used while the computer is working.
The CPU needs very fast access to data and instructions. If it had to fetch everything from slower storage every time, the computer would be too slow. Primary memory solves this problem by holding the data and instructions that are needed right now.
Primary memory acts like the computer’s short-term working area. It is much faster than secondary storage, but it usually stores less data and costs more per gigabyte.
Primary memory includes:
You will learn the differences between these later in the notes.
Secondary storage is used to keep data and programs for a long time. It is non-volatile, which means it keeps its contents even when the power is turned off.
This is needed because primary memory alone is not enough. For example, RAM loses its data when power is lost, so the computer needs somewhere permanent to keep:
Examples of secondary storage include:
Some secondary storage is removable, which means it can be taken out of one device and used in another. Examples include:
Removable storage is useful for:
However, removable storage can also be easier to lose or damage.
Secondary storage is often grouped into three main types.
Magnetic storage stores data by magnetising tiny areas on a surface.
A common example is the hard disk drive (HDD). Magnetic storage usually offers high capacity and a low cost per gigabyte, so it is good for storing lots of data. However, it is slower than solid state storage and can be damaged more easily because it often has moving parts.
Optical storage uses a laser to read or write data on a disc.
Examples include:
Optical storage is portable and useful for sharing or archiving data, but it usually has lower capacity and slower access than other storage types.
Solid state storage uses flash memory cells to store data electronically.
Examples include:
Solid state storage is fast, silent, and durable because it has no moving parts. It is often chosen when speed and shock resistance are important. The main drawback is a higher cost per gigabyte than magnetic storage.
Sign in to view full notes