Program in pascal [duplicate] - pascal

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What is that the Error of Illegal assignment and how to correct it?
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Just started to learn the Pascal programming language, I wrote an assignment that was given at the university, here is my assignment:
Build a program that will perform the following actions:
retrieve data of N elements (brand, name, atomic weight, density)
find the average density value
finding the three elements with the lowest atomic mass
writing the inputs and outputs to the text file "elements.txt"
wrote code for it, in theory everything should work, but it gives out some strange errors, if I have standard errors, I apologize for them.
program MINERALY_;
uses Crt;
const NMAX=200;
type MINERAL=record
NAZOV:string;
HUST:real;
ATOM:real;
ZNACKA:real;
end;
MINERALY=array[1..NMAX] of MINERAL;
var N,i,C,D:integer;
V:real;
MI:MINERALY;
S:string;
SUB:text;
PTVRD,CTVRD:real;
MINATOM:real;
begin
ClrScr;
Writeln('Program pre nacitanie mineralov a vypocet hodnot ich jednotlivych
vlastnosti.');
Writeln('===============================================================================');
{Vynulovanie hodnot}
CTVRD:=0;
PTVRD:=0;
MINATOM:=0;
{Nacitanie poctu mineralov}
Writeln;
Write('Zadajte pocet nacitavanych mineralov (Maximalne 200): ');
repeat
Readln(S);
Val(S,D,C);
if (C<>0) or (D<=0) or (D>200) then
begin
Writeln;
Writeln('Zadali ste nespravny pocet, alebo ste zadali nespravne znaky !');
Writeln('Hodnota moze byt od 1-200');
Write('Zadajte pocet mineralov este raz: ');
end;
N:=D;
until(N>0) and (N<=200) and (C=0);
{nacitavanie udajov, zistovanie max. a min. hodnot atd.}
for i:=1 to N do
begin
Writeln;
Write('Zadajte Znacku: ');
Readln(MI[i].ZNACKA);
Writeln;
Write('Zadajte nazov: ');
Readln(MI[i].NAZOV);
Write('Zadajte hustotu (musi byt vacsia ako 0): ');
repeat
Readln(S);
Val(S,V,C);
if (C<>0) or (V<0) then
begin
Writeln;
Writeln('Zadali ste nespravnu hodnotu, alebo ste zadali nespravne znaky !');
Write('Zadajte hustotu este raz (musi byt vacsia ako 0): ');
end;
until (V>0) and (C=0);
MI[i].HUST:=V;
CTVRD:=CTVRD+MI[i].HUST;
Write('Zadajte atómovou hmotnosťou (musi byt vacsia ako 0): ');
repeat
Readln(S);
Val(S,V,C);
if (C<>0) or (V<0) then
begin
Writeln;
Writeln('Zadali ste nespravnu hodnotu, alebo ste zadali nespravne znaky !');
Write('Zadajte atómovou hmotnosťou este raz (musi byt vascia ako 0): ');
end;
until (V>0) and (C=0);
MI[i].ATOM:=V;
if (i=1) then MINATOM:=MI[i].ATOM;
if (MI[i].ATOM<MINATOM) then MINATOM:=MI[i].ATOM;
PTVRD:=CTVRD/N;
Writeln;
Writeln('Vypocitane hodnoty: ');
Writeln('===================================');
Writeln;
Writeln('Priemerna tvrdost mineralov: ',PTVRD:2:2);
Writeln('Najnizsia hustota: ',MINATOM:2:2);
Assign(SUB,'mineral.txt');
Rewrite(SUB);
Writeln(SUB,'Nacitane mineraly: ');
Writeln(SUB,'===================================');
Writeln(SUB,'');
for i:=1 to N do
begin
Writeln(SUB,i,'. mineral: ');
Writeln(SUB,'Nazov: ',MI[i].NAZOV);
Writeln(SUB,'Znacka: ',MI[i].ZNACKA);
Writeln(SUB,'Tvrdost: ',MI[i].HUST:2:2);
Writeln(SUB,'Hustota: ',MI[i].ATOM:2:2);
Writeln(SUB,'');
end;
Writeln(SUB,'===================================');
Writeln(SUB,'Vypocitane hodnoty: ');
Writeln(SUB,'===================================');
Writeln(SUB,'');
Writeln(SUB,'Priemerna tvrdost mineralov: ',PTVRD:2:2);
Writeln(SUB,'Najnizsia hustota: ',MINATOM:2:2);
Close(SUB);
Writeln;
Writeln;
Writeln('Pre ukoncenie programu stlacte ENTER !');
Readln;
end.
Here are the errors this code gives me:
Compiling main.pas
main.pas(109,14) Error: Illegal assignment to for-loop variable "i"
main.pas(132,4) Fatal: Syntax error, ";" expected but "." found
Fatal: Compilation aborted
Error: /usr/bin/ppcx64 returned an error exitcode

Answer 1

Error: Illegal assignment to for-loop variable "i"
is when you are trying to change the value of i while the loop is still working.
since you didn't end; the loop you canno't change the value of i you can use another variable, j for example, unless your first for-loop is over and you forgot the end; key