Assuming that it takes 2 nsec to copy a byte, how much time does it take to completely rewrite that screen of an 80‐character x 25 line text mode memory‐mapped screen? what about a 1024 x 768 pixel graphics screen with 24‐bit color?

a.  0.04 msec

b. 23.59 msec

Explanation:

a. Text Mode

2 * 80 *25 = 4000 bytes

1 byte take 2nsec time so, 4000 bytes take

4000 * 10 nsec = 40000 nsec = 0.00004 sec = 0.04 msec

b. Graphics:

24 bit color

3 bytes per pixel

1024 * 768 * 3 = 2 359 296 bytes

2 359 296 * 10 nsec = 23592960 nsec = 0.02359296

sec =23.59 msec

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