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This chapter presents the following content: Resizing the vector, push_back function, parameters passing mechanism, primitive arrays of constants, multidimensional arrays, the standard library string type. | Lecture 09 Recap Resizing the Vector Push_back function Parameters passing Mechanism Primitive Arrays of Constants Multidimensional Arrays The Standard Library string Type Pointer Syntax in C++ To have a pointer point at an object, the target object's memory address must be known For any object obj , its memory address is given by applying the unary address-of operator & Thus &obj is the memory location that stores obj We can declare that an object ptr points at an int object by saying int *ptr; The value represented by ptr is an address using ptr before assigning anything to it invariably produces bad results Continued . Suppose we have declaration int x=5; int y=7; make ptr point at x by assigning to ptr the memory location where x is stored. Thus ptr = &x; / / LEGAL The unary dereferencing operator * access the data through pointer To dereference something that is not a pointer is illegal The * operator is the opposite of & Dereferencing works not only for reading values from an object, but also for writing new values to the object *ptr = 10; // LEGAL changed the value of x to 10 Continued . Declaration of pointer can be done as int x = 5; int y = 7; int *ptr = &x; / / LEGAL Wrong declaration int *ptr = &x; // ILLEGAL: x is not declared yet int x = 5; int y = 7; Continued . Wrong declaration int x = 5; int y = 7; int *ptr = x; // ILLEGAL: x is not an address Correct but not meaningful declaration int x = 5; int y = 7; int *ptr; // LEGAL but ptr is uninitialized Continued . A dereferenced pointer behaves just like the object that it is pointing at. So, following declaration will save x=15 x = 5; ptr = &x; *ptr += 10; Two more declaration of dereferenced operator *ptr +=1; *ptr ++; In the first statement the += operator is applied to *ptr, but in the second statement the ++ operator is applied to ptr Continued . If ptr1 and ptr2 are pointers to the same type, then following sets ptrl to point to the same location as ptr2 ptr1 = ptr2; Following assigns the . | Lecture 09 Recap Resizing the Vector Push_back function Parameters passing Mechanism Primitive Arrays of Constants Multidimensional Arrays The Standard Library string Type Pointer Syntax in C++ To have a pointer point at an object, the target object's memory address must be known For any object obj , its memory address is given by applying the unary address-of operator & Thus &obj is the memory location that stores obj We can declare that an object ptr points at an int object by saying int *ptr; The value represented by ptr is an address using ptr before assigning anything to it invariably produces bad results Continued . Suppose we have declaration int x=5; int y=7; make ptr point at x by assigning to ptr the memory location where x is stored. Thus ptr = &x; / / LEGAL The unary dereferencing operator * access the data through pointer To dereference something that is not a pointer is illegal The * operator is the opposite of & Dereferencing works not only for reading values from an .
