Error SP2-0310 ; explain to me why it was fixed by substituting ; with / (below) the line

I was executing

-- install.sql includes
start c:\TABLES\deletetables.sql;
commit;
start c:\TABLES\createtables.sql;
commit;

So i rung install
sql>start c:\install.sql

it was giving me an  SP2-0310: unable to open file "c:\TABLES\deletetables.sql;"

Then what i did is changing the install.sql to

-- install.sql includes
start c:\TABLES\deletetables.sql
/
commit;
start c:\TABLES\createtables.sql
/
commit;


and it worked fine.

Can you please tell me why is that happening ?