Simple Present Tense

What is present tense ? Present tense is principal function is to locate a situation or event in present time.in present tense have a formula : Subject + Main verb + Object

example :I write a letter. 
         He gets up early in the morning.
         Sun rises in east. 

in present tense had a negative side.

example :I do not write a letter.
         He does not get up early in the morning.
         Sun does not rise in east.