how natural to express an action
how much text to express action 

how easy to understand and follow program

aids in understanding to make a modification

e.g., symbolic constants, data abstraction, polymorphism

Arrays, Records, If-then-else, for/while loops

efficiency improving transformations

if-then goto
if-then-else, while, for

subprograms with parameters
exception handling
coroutines
concurrent units

begin -- the begin reserved word
:= -- the assignment operator
[A-Z][A-Z0-9]* -- an identifier
[0-9]+  -- an integer literal

E --> E '+' E
E --> E '*' E
E --> '(' E ')'
E --> Identifier