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Languages :: Pascal :: record numbers in pascal.....
By: skitz0 U.S.A.  Date: 28/04/2003 00:00:00  English  Points: 75 Status: Answered
Quality : Excellent
right here goes....this is my project...and what i need to do is have a search procedure (which i have tried to do in procedure "view cand")..but the only way i can search for candidates is if i search for the record numbers....is there any way that i can search by the candidate number(candrecord.candnum) or is there any way in which i can view the record number when i list all the candidates....any help will be appreciated....

program assignment;
uses crt;
type candrecordtype = record
name:string[40];
candnum:integer;
centrenum:integer;
subrefcode:string;
origmark:integer;
remarkmark:integer;
request:boolean;
origG:string;
remarkG:string;
yes:string;
recnum;integer;
end;

var
diskfile:file of candrecordtype;
candrecord:candrecordtype;
counter:integer;
choice:integer;
loop:integer;

procedure open;
begin
assign (diskfile, 'c:\windows\desktop\work\record.dat');
reset (diskfile);
end;

procedure listcand;
begin
reset(diskfile);
clrscr;
writeln ('candidates in database');
for loop :=0 to (filesize(diskfile)-1) do
begin
seek(diskfile,loop);
read(diskfile,candrecord);
writeln ('candidate name : ',candrecord.name);
writeln ('candidate number : ',candrecord.candnum);
writeln;
end;
readln;
end;

procedure addcand;
var
yes:string;
begin
clrscr;
writeln ('Add Candidate To Database');
writeln ('please enter candidate name');
readln (candrecord.name);
writeln ('please enter candidate number');
readln (candrecord.candnum);
writeln ('please enter centre number');
readln (candrecord.centrenum);
writeln ('please enter subject reference code');
readln (candrecord.subrefcode);
writeln ('please enter original mark');
readln (candrecord.origmark);
writeln ('please enter re-mark (leave blank if not yet marked)');
readln (candrecord.remarkmark);
repeat
writeln ('did the centre request the script back? y/n');
readln (yes);
if (yes='y') then candrecord.request:=true;
if (yes='n') then candrecord.request:=false;
until (yes='y') or (yes='n');
seek(diskfile,(filesize(diskfile)));
write(diskfile,candrecord);
writeln ('record saved');
readln;
end;

procedure viewcand;
var
number:integer;
begin
clrscr;
writeln('enter candidate number');
readln (number);
if number>(filesize(diskfile)-1) then
begin
writeln ('this record does not exist');
readln;
end
else
begin
reset(diskfile);
seek(diskfile,number);
read (diskfile,candrecord);
with candrecord do
begin
writeln ('candidate name : ',name);
writeln ('candidate number : ',candnum);
writeln ('centre number : ',centrenum);
writeln ('subject reference code : ',subrefcode);
writeln ('origional mark : ',origmark);
if remarkmark>0 then writeln ('remark : ',remarkmark)
else writeln ('remark : N/A');
writeln;
readln;
end;
end;
end;



begin
repeat
clrscr;
open;
writeln ('Ukab Database');
writeln ('1. add candidate to database');
writeln ('2. view all candidates');
writeln ('3. view individual candidate');
writeln ('4. exit');
readln (choice);
case choice of
1:addcand;
2:listcand;
3:viewcand;
4:exit;
end;

until choice=4

end.
By: VGR Date: 28/04/2003 07:41:00 English  Type : Answer
with direct access like in here, no.
You need an index.
Or to have sorted your records on candnum so that any algorithm can be used (dichotomy is first possibility)

For now, assuming you've none of the above, the answer is : yes, you can, but in stead of accessing directly (on record number) a precise record (no search), you've to search in ALL the recoprds (or at least until the candnum searched for is found, trivially)

something like

read (diskfile,candrecord);
if candrecord.candnum<>searchedvalue Then
while (NOT Eof(diskfile)) AND (candrecord.candnum<>searchedvalue) Do read (diskfile,candrecord);
// you get out either on positive candrecord.candnum=searchedvalue or on eof (not found)
By: skitz0 Date: 28/04/2003 07:57:00 English  Type : Comment
erm....still the same....when i search it for the record number.....but not for the candidate number....
By: VGR Date: 28/04/2003 09:27:00 English  Type : Comment
sorry, but it should work. show your current code
By: skitz0 Date: 28/04/2003 09:37:00 English  Type : Comment
erm...i got it runnin a different way now mate....but after trying your code a second time it does work (when i put it in the right place) hehe....so u get the points :)
By: VGR Date: 29/04/2003 05:03:00 English  Type : Comment
tsssk tsssk tsssk :D

thanks a lot

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