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# computer science - PowerPoint PPT Presentation

CSCI 1001. overview of. computer science. REPRESENTING DATA I. What do each of these mean:. VII. 7. How do computers represent data ?. Review: Deci mal. What does the digit sequence 563 mean? . 5×10 2 + 6×10 1 + 3×10 0. bit: a value that is either 0 or 1.

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Presentation Transcript

CSCI 1001

overview of

### computer science

REPRESENTING DATA I

What do each of these mean:

VII

7

How do computers represent data?

Review: Decimal

What does the digit sequence 563 mean?

5×102 + 6×101 + 3×100

bit: a value that is either

0 or 1

string: a sequence of bits

byte: a string of 8 bits

Binary

A bit string can represent a number:

110 =

1×22 + 1×21 + 0×20

A byte has the place values:

What is the smallest possible byte?

the largest?

Input: a positive integer N

• Find the largest k so that 2k ≤ N
• for each power_of_2 ∈ {2k,2k-1,…,1}:
• if N ≥ power_of_2 then:
• set N = N - power_of_2 and output 1
• else:
• output 0
• 3. stop.
• setp = 1 and k = 0
• whilep ≤ N/2:
• set p = p×2 and k=k+1

PRACTICE: 11011100, 93, 42

Base 16:

0,1,2,…,9,A,B,C,D,E,F

0x37

• = 5510

0x1A

• = 2610

0xC2

• = 19410

How many bits for a hex digit?

4 (a nibble)

Hex

Binary

Decimal

0x2C

10100011

217

ascii

1 Letter = One byte

“MINNESOTA” ⇒ 0x4D494E4E45534F5441

Moby Dick = 1,255,836 bytes

1

1

1

1011

0111

+

1

1

0

0

0

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