# Number 4.5

Base 2 notation

Converting base 10 to base 2 : basetentotwo
Converting base 2 to base 10 : base2calc

Secret Message

Every keyboard character on a computer is represented by a number code, with a number from 0 to 127 (base ten), that is, from 0 to 1111111 (base 2). These codes are referred to as ASCII codes (American Standard Code for Information Interchange). List of the codes found here: asciicodes

Students can write a message in words, translate it into the ASCII code number, then in turn translate this into base 2 numbers. For example, the ASCII code for Hello Kim would be
72 101 108 108 111 32 75 105 109.
Turning this into base 2 numbers, the coded message becomes:
01001000 01100101 01101100 01101100 01101111 00100000 01001011 01101001 01101101. Notice that here the zeros are always written in front so that each base 2 number has exactly eight digits. This 8-digit base 2 number is called a byte. Count how many bytes are in your name. The message Hello Kim has 9 bytes. This gives meaning to the size of computer files, such as 150 kB (kilobytes) or 1.4 MB (megabytes).

Indices

Factors and Multiples

Fractions

Ratio and circles