[\<- Notes 01/15](01-15.md)

---

# Structures Continued

- typedef can be used to give the structure an alias
	- For example:

```
typedef struct info{
	int number;
	char character;
	char string[10];
	int array[10];
} INFO;

...

INFO real_info;
INFO *p;
```

- In the above example, struct info is called "INFO"
- The same can be done using a `#define` statement:

```
#define INFO struct info

...

struct info{
	int number;
	char character;
	char string[10];
	int array[10];
};

...

INFO real_info;
INFO *p;
```

- Initializing a struct in one line:

```
struct info{
	int number;
	char character;
	char string[10];
	int array[10];
};

struct info i1 = {99, 'Z', "abc", {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}};
```

- Alternatively, you can set members one at a time:

```
struct info1, info2;
...
info1.number = 99;
info1.character = 'Z';
strcpy(info1.string, "abc");
for(i = 0; i < 10; i++){
	info1.array[i] = i;
}
```

- You can also copy one structure to another very easily:

```
info2 = info1;
```

- Now I want to print each member of `i1`:

```
printf("%d\n", i1.number);
printf("%c\n", i1.character);
printf("%s\n", i1.string);
for(i = 0; i < 10; i++){
	printf("%d\n", i1.array[i]);
}
```

- Arrays of structures can also be declared:

```
struct info lots_of_info[20];
lots_of_info[0].number = 17;
```

- Here is a struct in action:

```
struct simple{
	int value1;
	int value2;
}

int main(void){
	struct simple s1 = {10, 15};
	...
}
```

- Structures can be passed as an argument either as a "Call by Value" or "Call by Reference
- Example of "Call by Value":

```
void fun1(struct simple s){
	s.value1++;
	s.value2*=2;
}
```

- Example of "Call by Reference":

```
void fun1(struct simple *s){
	s->value1++;
	s->value2*=2;
}
```

- This is the same idea as passing variables as copies versus as pointers to memory