Your computer screen displays images through a grid of tiny squares called pixels, each assigned a numerical color value. Pictures are stored numerically in the computer, with black and white images easier to encode than color since black and white pictures can be represented by numbers showing consecutive black or white pixels, with the first number always denoting white pixels.

2. Your computer screen is made up of a grid
of tiny squares called ‘pixels’ (Picture
Cells). Each tiny square is given a
numerical value which determines it’s
colour

3. A computer can only store numerical information. A picture therefore is stored in a
numerical form. Black and white pictures are easier to de-code than colour. Look at the
picture below:
When coding a black and white
image, the numbers represent how many
pixels are consecutively either black or
white. The first number will always
represent the number of white pixels.