assign is a function that copy the external file content
to internal text variable,the delcaration like this:
assign(variable, file name);
let's go for the read function:
first ,when we want to read a file,we must be
reset the file variable,and also read/readln function
are used to read
like this
sample 1:
var
abc:text;
content:string;
begin
assign(abc,' BBQ.TXT'); {first BBQ.txt must be
persent because of reading
according to the function reset}
reset(abc);
readln(abc,content); {then
we use readln function to read a line in variable}
{If there are many lines in the program,or storing a article, a LOOPING
and array of "content" may be used for read the data.}
writeln('file content:',content );{output content}
close(abc);{remember to close the abc before program end!!
else the file may dead(data lost)!!
end.
let's go for the write function: a rewrite function is needed
to replace
the reset function,
sample2:
var
abc:text;
content:string;
begin
assign(abc,' BBQ.TXT'); {BBQ.txt can be absent ,if absent
,PASCAL will help you to create a new one else the pascal will overwrite
the old one according to the function rewrite}
rewrite(abc);
writeln('please enter a text here(1-79)');
readln(content);
writeln(abc,content); {then
we use writeln function to put a variable in line}
writeln('file content added:',content );{output content}
close(abc);
end.
when you want to completly kick out a file,Don't use dummy variable
for writing instead, use the function "Erase(variable text)" is most approriate!!
that's the end of this day, next day(sure?) we will talk about record and two data structure (linked list and list)