CMPS 002 - Computer Literacy
Prof. Paulo Franca
How much memory does it take?
To store a book (text):
1 page -> 70 characters per line x 40 lines per page
2800 characters (bytes per page) -> 2.8 KB ~ 3 KB per page
a book with 500 pages -> 3KB x 500 = 1500KB = 1.5 MB
One character is one byte. It is even possible to create codes to compress the amount of storage needed for a large text. For example, a book with 1.5 million characters could be compressed into, say, 1MB instead of 1.5MB
To store images you must somehow describe each of the pixels in the image: the location and color. Therefore, storage depends on the number of pixels and the number of colors. An image that has 1280 pixes horizontally and 1024 pixels vertically (resolution 1280x1024) contains 1280x1024=1,310,720 pixels.
If the picture is black and white, then you need only one bit per pixel or 1,310,720 / 8 = 163,840 Bytes (163.8KB); however, if the picture is in high color, you may need 3 bytes to represent each pixel, which would give a total of 3x1,310,720 = 3,932,160 Bytes (3.9MB ~ 4 MB).
The point is, it takes much more storage space to store a picture than text. The same book with 500 pages would require much more storage if there were pictures along with the words.
A picture is worth a thousand words? Try again ... assuming that a word has 10 characters, 4MB (one picture) could be good for 400,000 words!
Using a CD Rom:
CD Roms can usually accommodate 600 MB. How many books of 1.5MB each could be stored?
600 MB / 1.5 MB = 400 books
Using a DVD
DVD's can store 4.7 GB. How many books of 1.5 MB each could be stored?
4700 MB / 1.5 MB = 3133 books
You can find hard drives from 40GB to 750GB. How many books of 1.5MB could be stored in a 750 GB hard drive?
750000 / 1.5 = 500,000 books.
Pages of text that are scanned into a computer are treated as images. Therefore scanned
pages require more storage space than regular text. Roughly, a scanned page takes about