Unit 3 Computer systems
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What is meant by a “sign bit”?
The first Bit in a binary number that indicates if the number is positive or negative
Which sign bit do we use for negative numbers?
1
Which sign bit do we use for positive numbers?
0
What do Bit-mapped graphics do?
They store every pixel necessary to store an image
What is meant by the term resolution?
Resolution is used to state the total number of pixels in an image
Why are Bit-mapped graphics said to be “resolution-dependent”?
As once an Bit-mapped graphics’ resolution is created it is set and will not change
Why is compression of a Bit mapped graphic necessary?
• To reduce the size of an image so that it is less demanding of storage and memory • To reduce the file size of an image to allow faster transmission across a network
What are the different types of Compression of bit-mapped graphics/
• Run length encoding (RLE) • Lempel, Ziv, Welch (LZW)
Where can Run length encoding compression be used?
if a block of pixels in a sequence are the same colour
What does LZW compression do?
LZW compression will store patterns of repeated colours and store them in an index where they can be looked up
What are the factors that affect computer performance?
• number of processors • Width of Data-bus • Cashe memory • Clock speed
Why does an increased number of processors increase performance?
As by increasing the number of processors, more data can be processed at one time meaning that the overall speed of the machine is faster
Why does increasing the width of the data bus increase the performance of the computer?
By increasing the data bus, you are increasing the amount of data that can be passed between the processors and main memory
What does increasing cashe memory have to do with increasing computer performance?
Cache is a memory that is closer to the CPU than RAM and holds instructions for the CPU, cashe memory improves the performance of the computer as more cashe memory means that more instructions can be held in cashe and cashe is easier to obtain instructions from than RAM, this also saves time improving the processing speeds