dereference

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dereference

(programming)
To access the thing to which a pointer points, i.e. to follow the pointer. E.g. in C, the declarations

int i; int *p = &i;

declare i as an integer and p as a pointer to integer. p is initialised to point at i ("&i" is the address of i - the inverse of "*"). The expression *p dereferences p to yield i as an lvalue, i.e. something which can appear either on the left of an assignment or anywhere an integer expression is valid. Thus

*p = 17;

would set i to 17. *p++ is not the same as i++ however since it is parsed as *(p++), i.e. increment p (which would be an invalid thing to do if it was pointing to a single int, as in this example) then dereference p's old value.

The C operator "->" also dereferences its left hand argument which is assumed to point to a structure or union of which the right hand argument is a member.

At first sight the word "dereference" might be thought to mean "to cause to stop referring" but its meaning is well established in jargon.

dereference

To go to an address before performing the operation. For example, in C programming, a dereferenced variable is a pointer to the variable, not the variable itself. The expression int Num; declares an integer variable named "Num." The expression *pNum = &Num; places the address of the variable Num (not its contents) into the pointer. The ampersand is the "address of" operator.

Another example is found in the tar archiving program. The dereference switch causes files referenced by symbolic links to be archived rather than the symbolic link itself. The term always refers to "following the link" in order to obtain the intended resource. See symbolic link.