Copyright © 2006, HaiVDC 1 Computer fundamentals Data Representation in Computers Copyright © 2006, HaiVD C 2 Objectives Introduction (Bit, Byte, KB, MB, GB) The Decimal Number System The Binary Number System Number Conversion between Number Systems Data Storage Binary Arithmetic Unit of Information Copyright © 2006, HaiVD C 3 Data Representation Data is stored in a computer in binary format as a series of 1s and 0s. Computers use standardized coding systems (such as ASCII) to determine what character or number is represented by what series of binary digits. Data is stored in a series of 8-bit combinations called a byte. Every letter, number, punctuation mark, or symbol has its own unique combination of ones and zeros. Copyright © 2006, HaiVD C 4 Data Representation On Off A bit or binary digit has one of two values, zero or one A byte is the smallest addressable unit of memory (8 bits) ASCII provides for 256 (or 2 8 ) characters 01000001 – A 01000010 – B etc. Copyright © 2006, HaiVD C 5 Memory Bits and Bytes 8 Bits = 1 Byte Copyright © 2006, HaiVD C 6 Memory Bits and Bytes Bits are switches turned ‘on’ or ‘off’ ON bits are said to be in a 1 state OFF bits are said to be in a 0 state Copyright © 2006, HaiVD C 7 Memory Bits and Bytes ON bits are said to be in a 1 state OFF bits are said to be in a 0 state 0 0 0 1 11 00 Combination of 1’s and 0’s represent the letters, numbers, and special characters. Allows for 256 combinations. Copyright © 2006, HaiVD C 8 Bits and Bytes 8 bits = 1 Byte (1 keyboard character) 1,024 bytes = 1 Kilobyte (1K) 1,024 K = 1 Megabyte (MB) 1,024 MB = 1 Gigabyte (GB) Copyright © 2006, HaiVD C 9 Memory Transient (erased when power turned off) Consider a UPS (uninterrupted power supply) Measured in bytes 1 Kilobyte = 2 10 characters (~1,000 bytes) 1 Megabyte = 2 20 characters (~1,000,000 bytes) 1 Gigabyte = 2 30 characters (~1,000,000,000 bytes) Need 256Mb or 512Mb of RAM Keep multiple programs & data files in memory Graphic-intensive programs demand a lot of memory The Original PC had 16Kb of memory Copyright © 2006, HaiVD C 10 The Decimal Number System In the decimal system use from 0 to 9 We consider the number: 365 (3x100) + (6x10) + (5x1) = 365 (3x10 2 ) + (6x10 1 ) + (5x10 0 ) = 365 Thus as we move one position to the left, the value of the digit increases by ten times The value of each digit in the number system is determined by: - The digit itself - The position of the digit in the number itself - The base/radix of the system . Copyright © 2006, HaiVDC 1 Computer fundamentals Data Representation in Computers Copyright © 2006, HaiVD C 2 Objectives Introduction. HaiVD C 3 Data Representation Data is stored in a computer in binary format as a series of 1s and 0s. Computers use standardized coding systems (such as