$1)$ What is the difference between syntax and semantics?

$2)$ Why is it important for a grammar to be unambiguous?

$3)$ Show that the following grammar is ambiguous $$ show two distinct parse

trees for one terminal string.

$->+|*|()|$ a $|$ b$|$ c

$4)$ Show that the following grammar is ambiguous $$ show two distinct parse

trees for one terminal string.

E$->$ E $+$ E $|$ id

$5)$ Write a grammar for the language consisting of strings over the alphabet $\{$a$,$b$\}$

where all strings start with the letter a and can have a$$s and b$$s after.

$6)$ Write a grammar for the language over the alphabet $\{$a$,$b$,$c$\}$ consisting of

strings that start and end with the letter a and have a$$s b$$s c$$s in between.

$7)$ Write a grammar for the language over the alphabet $\{$a$,$b$,$c$\}$ consisting of

strings where every b is immediately followed by the letter c

$8)$ Write an EBNF statement for a C$++$ float constant.

$9)$ Compute the weakest precondition for the following assignment statement

given the postcondition.

y $=2$y $1\{$ y $>1\}$

$10)$ Compute the weakest precondition for the sequence of statements:

$($Statement $1)$ b $=2$b $+1$;

$($Statement $2)$ b $=$ b$-3\{$b $<0\}$

$11)$ Compute the weakest precondition for the selection construct.

if $($a $==5)$

b $=2$b $+1$

else

b $=2$b;

$\{$b $>1\}$