representation of data in computer systems notes

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  • basic unit is 0 or 1- this is a binary digit or bit
  • 4 bits - nibble
  • 8 bits- byte
  • 1024 bytes- kilobyte
  • 1024 kilobytes- megabyte
  • 1024 megabytes- gigabyte
  • 1024 gigabytes- terabyte


binary to denary- write out into a table and then add up the headings with totals of 1

denary to binary- divide by 2 repeatedly noting the remainder until the answer is 0. the answer is the remainder column starting at the last value

adding binary numbers- use column method. you can carry 1's. number that comes out with more than 8 bits is called an overflow and it is an error

hexadecimal numbers- base 16 system. uses values 0-9 and then a-f.

hexadecimal to denary- split into separate values and times by the heading. then add these values together

denary to hexadecimal- divide by 16 repeatedly and record the remainders until the answer is 0.


  • it is important that systems agree on the codes being used for characters if the data is to make sense
  • in 1960 the American Standards Association agreed on a set of codes to represent the main character set used in telegraph systems
  • ASCII- American Standard Code for Information Interchange. was agreed to deal with basic textual messages and included codes for all the main alphabetic characters, upper and lower case; all the numeric symbols, 0-9; 32 punctuation and other symbols…


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