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docs/blog/posts/pointer.md

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+---
+date: 2024-10-05
+categories:
+  - C
+  - pointers
+---
+
+# Pointers
+
+- Pointer: group of cells that hold
+
+```c
+p = &c // & gives address of an object (=c)
+```
+
+- `*object`: indirection (dereferencing) operator
+  - access the object which pointer points to
+
+```c
+int x = 1, y = 10;
+int *p; // p is a pointer to int
+
+p = &x // p points to x (=1)
+y = *p // x = y = 1
+```
+
+- **Every pointer points to a particular object**
+
+```c
+int x = 1
+int *p; // declaration
+
+p = &x;
+*p = *p + 10; // x = x + 10
+```
+
+## Pointers-functions
+
+- Using pointers as arguments, you can modify parameters even if c follows call by value rule
+
+```c
+f(&a[2]) == f(a + 2)
+
+f(int array[]) == f(int *arr)
+```
+
+## Pointers-arrays
+
+- Pointer is almost equal to array except one difference.
+- The difference is that pointer is variable so it can be passed as arguments.
+- Example
+
+```c
+int *pa;
+pa = &a[0] // == (pa = a)
+
+&a[i] == a + i
+a[i] == *(a + i)
+
+*(pa + i) == a + i
+*(pa + i) == pa[i]
+```
+
+- String: arrays which contain character
+
+```c
+char s[] == char *s
+```
+
+reference: C programming language 2d edition