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A pointer a pointing to the memory address associated with a variable b, i.e., a contains the memory address 1008 of the variable b.In this diagram, the computing architecture uses the same address space and data primitive for both pointers and non-pointers; this need should not be the case.
In the C programming language, struct is the keyword used to define a composite, a.k.a. record, data type – a named set of values that occupy a block of memory. It allows for the different values to be accessed via a single identifier, often a pointer. A struct can contain other data types so is used for mixed-data-type records.
The element pc requires ten blocks of memory of the size of pointer to char (usually 40 or 80 bytes on common platforms), but element pa is only one pointer (size 4 or 8 bytes), and the data it refers to is an array of ten bytes (sizeof * pa == 10).
In C++, classes can be forward-declared if you only need to use the pointer-to-that-class type (since all object pointers are the same size, and this is what the compiler cares about). This is especially useful inside class definitions, e.g. if a class contains a member that is a pointer (or a reference) to another class.
typedef is a reserved keyword in the programming languages C, C++, and Objective-C.It is used to create an additional name (alias) for another data type, but does not create a new type, [1] except in the obscure case of a qualified typedef of an array type where the typedef qualifiers are transferred to the array element type. [2]
On C compilers targeting the 8086 processor family, far pointers were declared using a non-standard far qualifier; e.g., char far * p; defined a far pointer to a char. The difficulty of normalizing far pointers could be avoided with the non-standard huge qualifier. On other compilers it was done using an equally non-standard __far qualifier. [2]
However, every C and C++ compiler supports a more clear and concise mechanism to declare function pointers: use typedef, but don't store the pointer as part of the definition. Note that the only way this kind of typedef can actually be used is with a pointer - but that highlights the pointer-ness of it.
In the C programming language, restrict is a keyword, introduced by the C99 standard, [1] that can be used in pointer declarations. By adding this type qualifier, a programmer hints to the compiler that for the lifetime of the pointer, no other pointer will be used to access the object to which it points. This allows the compiler to make ...