C Pointers Flashcards
What is a pointer?
A data type that contains a memory address
What do we use pointers for?
To indirectly get to the values of variables
When we declare an array, is the index automatically declared?
No, declaring a variable doesn’t create a pointer to the variable.
I can manipulate the index value without changing:
the array value
I can change pointer values without affecting:
the memory data
What do the * and -> operators do?
They say “look in memory for” as the array name does with [] notation for arrays.
With pointers, how many values are we dealing with?
Two; the address stored by the pointer and the value at the address the pointer points.
What is the & operator used for?
To give us the memory address of a variable
What is * used for?
Used to tell it to look through the pointer to the underlying data
Where do we include *?
Right before the variable name in the declaration.
What does this do?
int *integer_pointer;
Declares a place to store an address and the thing that is at that address is an integer.
What must we assign a pointer?
A memory address
How do we get a variable’s memory address?
Precede it with &
How do we set a pointer value in C code?
int *integer_pointer;
int a;
integer_pointer= &a;
How do we read or change underlying data?
Precede the variable name with a *
Example: int *integer_pointer; int a; int b = 20; integer_pointer = &b; a = *integer_pointer; *integer_pointer = 10;
How do we declare a pointer?
int *p;
void *q;
How do we dereference a pointer?
int *p;
*p = 7;
How do we assign a pointer from a regular variable?
int *p;
int a;
p = &a;
What is used for a non-existent memory address?
A value from NULL (from sodlib.h)
What are the two ways of declaring a function in C?
Include all of the code for a function before it is used
Define a prototype of the function at the top of the C file and then give the code later.
How do we compile with multiple C files in one gcc command?
gcc -o executable file1.c file2.c file3.c
How do we read in C files?
#include "filename.h" Note the "" instead of
What items are in .h files?
- Constant Definitions
- TYpe definitions
- Function prototypes
- # include statements for other .h files
What are not in .h files?
Function implementations
What are the five steps in the compilation process?
Pre-process Compile Assemble Link Load
