Re: Pointers to "why C behaves like that ?"

"jacob navia" <jacob@jacob.remcomp.fr>
15 Nov 2002 00:40:39 -0500

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Pointers to "why C behaves like that ?" skwong@sun80.acae.cuhk.edu.hk (WONG SAI-KEE) (2002-11-12)
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From: "jacob navia" <jacob@jacob.remcomp.fr>
Newsgroups: comp.compilers
Date: 15 Nov 2002 00:40:39 -0500
Organization: Wanadoo, l'internet avec France Telecom
References: 02-11-059
Keywords: design
Posted-Date: 15 Nov 2002 00:40:39 EST

> Why the C lang behaves like that:
> We need to delare variable in advance, in contrast to other
> lang, the program simply use without declaring it.
>


suppose this code:


void updateAccount(newAmount)
{
        CurrentAmount = ReadCurrentAccount(database);
        CurrentAmunt =CurentAmount+newAmount;
        StoreDatabase(CurrentAmount);
}


You see the problem?


A typo in the spelling of the variable "CurrentAmunt" in line 2
creates a new variable "CurrentAmunt" that receives the result of the
addition. Since the CurrentAmount variable is stored, the account
receives a wrong value, and there is NO WAY to spot this bug until
runtime!


This means that any error when writing down the name of a variable is
a fatal error that will never be spotted. C prevents this by requiring
you to explicitly state the names you want at least twice!

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