There are two main operators for working with pointers.The operator is used when declaring a pointer and when dereferencing a pointer.Dereferencing can be used to either indirectly get a value from the pointer address or to assign a value to the pointer address. In this example we have used dereferencing to both get and set values.
For a compiler, a variable is a symbol for a starting memory address.
The compiler knows two things about any variable, the name and the type. Back when C was created, computers were much slower. Programmers needed to be much more efficient at solving problmes.
For , tells the compiler how much memory to store starting at that address. The more detailed answer has to do with call semantics. When you call a function in C, the value of any parameters are literally copied into the function’s call stack. Pass a char and 1-byte is copied into the function.
A C compiler converts C source code to assembly source code. What happens when you need to pass a 100k element int array into a function?
In this post we will start with variables and memory. The location that is allocated is the variable’s memory address.
Pointer Assignment In C
Most programmers will say a variable is a name for a piece of data that can change in a program.
For 64 bit systems, like most are these days, pointers will be 8-bytes or 64-bits. It is telling the compiler, “I have the address of a variable in the pointer.
The // declare an int pointer name ptr int *ptr; // declare an int with the value of 1 int val = 1; // get the address of the val variable and store it in ptr ptr = &val; // dereference the ptr variable to get the int value at the address stored int deref = *ptr; // dereference the ptr variable to set the int value at the address stored *ptr = 2; operator to get the address-of a variable of the correct type. I want to access that pointed-to address either to get a value or set a value “.
During that conversion variable names are converted to relative memory addresses. Don’t worry, you don’t need to know assembly to know pointers. C programs have different types of variables including ints, floats, arrays, chars, structs, and pointers. You don’t want to have to copy the 400,000 bytes into a function. Instead you have a pointer which references the array.
An int holds an integer number, a float holds a floating point decimal number. A pointer is a variable that holds the memory address of another variable. The pointer, all 4 or 8 bytes of it, is copied into the function where it can be dereferenced and the array accessed. Don’t pass a copy of the large struct in, pass in a pointer to the struct.