Re: [sheflug] a- level questions need help

[Alex Hudson <nospam [at] alexhudson.com>]

On Sat, May 19, 2001 at 09:56:02PM +0100, Sammy wrote:
> I need a clear definition of recursion and cache memory and how it works

Getting sheflug to do your homework eh? :)

Recursion: defining a function in terms of itself, kind of. It's a bit like
proof by induction. Don't confuse recursivity with iterative or functional
programming - procedural and recursive function can be defined in either
iterative or functional languages. If i was anal, I'll call them orthogonal.

Cacheing works on the priniciple that you use a small number of things
often. So, the things you use often you keep nearby to increase the overall
speed. Having a fast piece of RAM (for example) is expensive, whereas slow
RAM is less expensive, so if you have a small area of fast RAM and a large
area of slower RAM you can use a cacheing scheme to make best use of the
small area (the cache). Lookup anything on microprocessor design -
particularly virtual memory, translation lookaside buffers and opcode
loading.

> and any pointer to databas normalisation.

Anything on databases will cover it.

> please help i haven't got any decent difinition and am having problem with
> normalisation

If a database is normal, it has a set of known properties - for example, no
piece of information is repeated. So, if you have a database of customers,
you don't store their name more than once. Normalisation is the process of
taking a database design and making it normal - there are a set of rules
which you follow to achieve normal forms (the degree of normality within the
database).

Cheers,

Alex.
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