Cirrus Logic CS485 Instrukcja Użytkownika Pobierz pdf (Strona 27)

CS485G Spring 2015 27

27 Arrays

1. Lecture 15, 2/23/2015

2. C declaration: T myArray[L], where T is some type and L is the

number of elements (the ﬁrst is number 0).

3. Contiguously allocated region of L × sizeof(T ) bytes.

4. Examples

declaration length

char string[12] 12

int val[5] 20

double a[3] 24

char

p[3] 12 (on x86)

char

p[3] 24 (on x86 64)

5. C syntax, given int val[5]; stored starting at location x, contain-

ing 1, 2, 3, 4, 5.

expression type value

val[4] int 3

val int * x

val+1 int * x+4

&val[2] int * x+8

val[4] int 5

val[5] int garbage

(val+1) int 2

val + i int * x+4i

6. Using the same type for several arrays

1 #define ZLEN 5

2 typedef int myArrayType[ZLEN];

3 myArrayType cmu = { 1, 5, 2, 1, 3 };

4 myArrayType mit = { 0, 2, 1, 3, 9 };

5 myArrayType uky = { 9, 4, 7, 2, 0 };

It’s possible, but not guaranteed, that the three arrays are consecutive

in memory.

7. Simple example: return uky[dig];

# assume d = uky

# assume a = dig

movl (%edx,%eax,4),%eax # a = uky[dig]

1 2 ... 22 23 24 25 26 27 28 29 30 31 32 ... 66 67

Brak uwag

Cirrus Logic CS485 Instrukcja Użytkownika Strona 27