A Level Computing: What is a hashing algorithm?

I hate algorithums. There the only thing I don't understand

We should make a topic for those odd questions that catch everyone out. Im in the process of doing 20 practice papers and in the 1st one i've found 2 that completely caught me out

Reply 2

OP

OMGWTF

I hate algorithums. There the only thing I don't understand

We should make a topic for those odd questions that catch everyone out. Im in the process of doing 20 practice papers and in the 1st one i've found 2 that completely caught me out

Yeah i know, some algorithms are ok, but this hashing one i just do not get the use for.

What questions have caught you out?

Yeah this can be the thread for a level computing revision questions.

Cheers

Flukey :smile:

Reply 3

Ziggy Stardust

Hashing algorithm. Isn't that used for passwords? Yeah, tis!

Reply 4

azukibean

6

hmm....i would think a hashing algorithm is where the record has to go through some form of algorithm(which can be anything) to store itself...

but i've heard that one possible hashing method is the 'division/remainder method'. This is where the record is divided by the total number of addresses on the file and the remainder of this would be taken as the address of the record.

in my textbook it shows an example...

record number is 75481
1000 records

so 75481/1000 = 75 remainder 481

therefore the address is 481.

MOD 1000...well you cant just have that by itself...it's basically taking a remainder of a number...as i shown above...

75481 MOD 1000 would mean...
75481 divided by 1000...and taking the remainder which is 481 (as mentioned above)

I hope this made sense....i'm terrible at explaining things but i tried =D

Reply 5

The Difference Between Archiving and Backuping

This is what I put, Archiving is saving data for use later wheras backing up is saving data incase of an emergency to stop all data being lost

Thats one of them. BTW does anyone know where i can get the AQA Grade Boundaries, i've got all the exam papers and mark schemes

Reply 6

OP

jakayaki

hmm....i would think a hashing algorithm is where the record has to go through some form of algorithm(which can be anything) to store itself...

but i've heard that one possible hashing method is the 'division/remainder method'. This is where the record is divided by the total number of addresses on the file and the remainder of this would be taken as the address of the record.

in my textbook it shows an example...

record number is 75481
1000 records

so 75481/1000 = 75 remainder 481

therefore the address is 481.

MOD 1000...well you cant just have that by itself...it's basically taking a remainder of a number...as i shown above...

75481 MOD 1000 would mean...
75481 divided by 1000...and taking the remainder which is 481 (as mentioned above)

I hope this made sense....i'm terrible at explaining things but i tried =D

Oh i get you, you exlpained it very well. Shall rep you!

Thanks for that, much appreciated. It's crystal clear now!

Flukey :smile:

Reply 7

One other thing.

CD ROM, not CD. That caught me out, even Compact Disc isn't acceptable

Reply 8

OP

OMGWTF

The Difference Between Archiving and Backuping

This is what I put, Archiving is saving data for use later wheras backing up is saving data incase of an emergency to stop all data being lost

Thats one of them. BTW does anyone know where i can get the AQA Grade Boundaries, i've got all the exam papers and mark schemes

grade boundaries:

<40% U
=>40% E
=>50% D
=>60% C
=>70% B
=>80% A

Note: => is greater than or equal too.

Reply 9

OP

OMGWTF

The Difference Between Archiving and Backuping

This is what I put, Archiving is saving data for use later wheras backing up is saving data incase of an emergency to stop all data being lost

Thats one of them. BTW does anyone know where i can get the AQA Grade Boundaries, i've got all the exam papers and mark schemes

Yeah thats a good explanation, the exam board should accept that. Nice one! :smile:

OMGWTF

One other thing.

CD ROM, not CD. That caught me out, even Compact Disc isn't acceptable

oh right didn't know that, thanks for the advice.

Cheers

Flukey :smile:

Reply 10

trev

15

OMGWTF

The Difference Between Archiving and Backuping

This is what I put, Archiving is saving data for use later wheras backing up is saving data incase of an emergency to stop all data being lost

Thats one of them. BTW does anyone know where i can get the AQA Grade Boundaries, i've got all the exam papers and mark schemes

Refer to these examiners report for the grade boundaries: http://www.aqa.org.uk/qual/gceasa/comp_exam.html Click on anyone to see the grad boundaries, it is located near the end of the report, and you should see a few tables.

I can't believe the exam is in 2 days time. Good luck!

Reply 11

Chiral

but those grade boundries are UMS not raw.

Archiving is copying the data to whatever (CD-R, tape drive, etc.) THEN REMOVING THE ORIGINAL DATA

Backing up is copying the data to whatever, and KEEPING THE ORIGINAL DATA 'online'

Reply 12

trev

15

The A-level computing 5th edition text book has definitions on archiving and back up. They are:

archiving: removing a file from an online storage and used for future reference
backing up: making a copy of a file to guard against data loss from accidents or deliberate damage

Reply 13